DOF and Cropping take 2

Started 10 months ago | Discussions
lacix
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Re: DOF and Cropping take 2
In reply to MightyMike, 10 months ago

Exactly!

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Great Bustard
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Equivalence.
In reply to Ian Stuart Forsyth, 10 months ago

Ian Stuart Forsyth wrote:

http://www.dpreview.com/forums/post/53084843

continued from the post above

Just a highlight key points I would like to address

red is Ian

Green is GossCTP

and Black awaldram

But I see it as equivalent please see below

Do you really believe this website above , I mean really ?

How accurate is the information they provide ?

I haven’t read over the whole page so I will trust you when you say with everything you have provided here as true. But what if I can prove that they are wrong (if I rely on what you have said above that cropping has no effect on DOF)

What if I crop my k5 shot with 300mmF2.8 by a factor of 1.8

K5 shot with the 300mm F2.8 Cropped by 1.8 will have a resulting image that would share the same DOF and FOV as a k5 shot with a 540mm lens at F5

Below is a screen grab using the DOF calculator of a trusted site that I used more than once & that I believe to be true

As you can see that it calculates the same equivalent of lens and F stop as I had calc’d

Here is a quote from the site

“As sensor size increases, the depth of field will decrease for a given aperture (when filling the frame with a subject of the same size and distance). This is because larger sensors require one to get closer to their subject, or to use a longer focal length in order to fill the frame with that subject. This means that one has to use progressively smaller aperture sizes in order to maintain the same depth of field on larger sensors. The following calculator predicts the required aperture and focal length in order to achieve the same depth of field (while maintaining perspective).

As an example calculation, if one wanted to reproduce the same perspective and depth of field on a full frame sensor as that attained using a 10 mm lens at f/11 on a camera with a 1.6X crop factor, one would need to use a 16 mm lens and an aperture of roughly f/18. Alternatively, if one used a 50 mm f/1.4 lens on a full frame sensor, this would produce a depth of field so shallow it would require an aperture of 0.9 on a camera with a 1.6X crop factor — not possible with consumer lenses!”

And a reminder that whether you crop an image in the camera or in post with PS you are altering the size of the format, just as many do with a D7100 or a D800 in camera or during post

Now which site do I believe yours or mine?

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens). However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor:

25mm f/1.4 on mFT (4/3) is equivalent to 31mm f/1.8 on 1.6x (Canon APS-C), 33mm f/1.9 on 1.5x (APS-C for everyone else), and 50mm f/2.8 on FF (FX), where "equivalent to" means:

  • The photos all have the same diagonal angle of view (25mm x 2 = 31mm x 1.6 = 33mm x 1.5 = 50mm) and aperture diameter (25mm / 1.4 = 31mm / 1.8 = 33mm / 1.9 = 50mm / 2.8 = 18mm).
  • The photos all have the same perspective when taken from the same position.
  • The photos all have the same DOF (as well as diffraction softening) when they are taken from the same position with the same focal point and have the same display size.
  • The photos all have the same motion blur for the same shutter speed (regardless of pixel count).
  • The same total amount of light falls on the sensor for the same DOF and shutter speed.
  • The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).
  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.
  • The same total light will result in the same noise for equally efficient sensors (regardless of pixel count and regardless of the ISO setting).
  • If the 25mm lens at f/1.4 has twice the resolution as the 50mm lens at f/2.8 on FF, 1.33x the resolution of the 33mm lens at f/1.8 on 1.5x, and 1.25x the resolution of the 31mm at f/1.8 on 1.6x, the sensors have the same pixel count and same AA filter strength, then all systems will also resolve the same detail.
  • Other elements of IQ, such as bokeh, color, distortion, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".
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justin23
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Re: DOF and Cropping take 2
In reply to lacix, 10 months ago

The way I see this is, say you are on an african safari with a FF camera and a APS-C camera and you have the same lens on each camera

You see a lion in the distance and the shot from the APS-C is good. With the FF you crop it and magnify it to the same size and guess what you get the same image with same FOV and same DOF.

When you think about it the same image is projected onto the focal plane and in one camera you capture more of that image than the other camera. but its still the same image captured at the same focal length with the same aperture.

The whole equivalence thing is about using a lens on the FF camera rather than using a crop and magnify, yet you'll get the same image with a longer lens and smaller aperture. There are many reason why this would be worse or better.

So we've been shown using the same lens and cropping and magnifying gives the same results, regardless of the format and this makes complete sense. Because the lens is not going to change the image it produces base on what is capturing the image.

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moving_comfort
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Awaldram
In reply to Great Bustard, 10 months ago

Great Bustard wrote:

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens). However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor:

25mm f/1.4 on mFT (4/3) is equivalent to 31mm f/1.8 on 1.6x (Canon APS-C), 33mm f/1.9 on 1.5x (APS-C for everyone else), and 50mm f/2.8 on FF (FX), where "equivalent to" means:

  • The photos all have the same diagonal angle of view (25mm x 2 = 31mm x 1.6 = 33mm x 1.5 = 50mm) and aperture diameter (25mm / 1.4 = 31mm / 1.8 = 33mm / 1.9 = 50mm / 2.8 = 18mm).
  • The photos all have the same perspective when taken from the same position.
  • The photos all have the same DOF (as well as diffraction softening) when they are taken from the same position with the same focal point and have the same display size.
  • The photos all have the same motion blur for the same shutter speed (regardless of pixel count).
  • The same total amount of light falls on the sensor for the same DOF and shutter speed.
  • The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).
  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.
  • The same total light will result in the same noise for equally efficient sensors (regardless of pixel count and regardless of the ISO setting).
  • If the 25mm lens at f/1.4 has twice the resolution as the 50mm lens at f/2.8 on FF, 1.33x the resolution of the 33mm lens at f/1.8 on 1.5x, and 1.25x the resolution of the 31mm at f/1.8 on 1.6x, the sensors have the same pixel count and same AA filter strength, then all systems will also resolve the same detail.
  • Other elements of IQ, such as bokeh, color, distortion, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

.

So Awaldram, you've called Falk's paper a 'fallacy', although I doubt you'd really think the whole thing could be a fallacy. I'm left with not knowing what parts of it you agree with or not. So let's move to the above - what do you think is false or 'crackpot' to use your word, in the above?

You seem to not agree with:

  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.

Based on what you said here (in reference to Ian stating a correct equivalent relationship he layed out which would have required the FF image to use ISO 225 to match the aps-c ISO 100 with the same total amount of light) :

...Ian/MC said FF required iso225 to match iso100 aps-c - wrong

...On another subject you keep saying iso100 on aps-c = iso 225 on FF

...Again your doing some kind of weird 'equivalence' to push some FF agenda

And you seem to disagree with the following: "...However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor"

Based on what you said here:

...Ian/MC said DoF is a function of sensor size - wrong

...I said an f2.8 lens is an f2.8 lens on any sensor - Check Proved

...Ian/MC stated a lens alters it behaviour and f2.8 is not the same but depends on sensor size - yet again wrong.

So, anything else you disagree with in the above (or can you be more specific about what you disgaree with in Falk's paper? )

.

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Mark Ransom
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Re: DOF and Cropping take 2
In reply to awaldram, 10 months ago

I think your calculations for motion blur are off. The motion blur is caused by the motion of the camera, which is independent of sensor size - if the sensor is 1.5x smaller then the blur must also be 1.5x smaller to maintain the same visibility across the frame. So if you need 1/400 for FF, you'll also need 1/400 for APS-C and 1/400 for the Q.

Anti-shake technology may mean the 1/FL guideline can be loosened a bit, but again that should be the same for all sensor sizes.

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Ian Stuart Forsyth
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Re: Cropping from within a format (101)
In reply to James O'Neill, 10 months ago

James O'Neill wrote:

Ian Stuart Forsyth wrote:

James O'Neill wrote:

Ian Stuart Forsyth wrote:

As you can see that they share the same FOV and DOF now why is this? (bear with me if you Know)

They are all the same because you have not achieved the same FoV by changing focal length but by cropping, In one you have cropped once and the rest you have cropped twice.

The test was not to change the FOV by FL see below

The smaller the fragment of the image you zoom in to, the easier it is to see what is out of focus. The cereal is just as out of focus in the whole frame as it is in the cropped-down-to-Q frame, but at such you can't see it in the whole frame.

This does not prove F4 on any of the 4 format sizes is the same but rather that if we crop an image from format and compare it to another format at the same FOV that the DOF will be the same only because the share the size portion of the project image circle from the 55mm F4 lens (same format size). So at the end of the day we still have F2.8 is not equal to F2.8 across formats.

That's not the clearest phrasing in the history of English. A small image from the camera - whether it started small or was cropped from a bigger one - has to be magnified more than large one to fill the same size sheet of photographic paper or computer screen. As you magnify what was in the D.o.F zone because you couldn't see it was slightly out of focus is revealed to be blurred.

D.o.F isn't some magical "What's in is perfectly focused" zone , but "What's in is so slightly out of focus you don't notice". The same focus "error" with the same lens and same aperture will produce the same distance of blurring on the film or sensor: 0.02 mm of blur is harder to see on a 33x44mm image than a 3x4 mm one. Hence all d.o.f. calculations use a circle of confusion size which depends on image size : and that is image size after all cropping has been done.

The test showed this.

Taking images with 4 different format sizes and cropping them all to the same FOV

You didn't though. You took an image and cropped it to 4 sizes. Then you cropped the large size a second time, so cropped the same image down to the same image in 4 different ways.

yes and the reason why is below

You can argue it both ways - if you magnify a section of the image that has a smaller FoV but it is the magnification - or more accurately the change in workable Circle of Confusion size - that has the impact on DoF. If you change the FoV by changing image size and not focal length , it reduces the circle size.

By cropping the 645 to this FOV you are using another format,…. And cropping the Q to the same FOV you are using the same format size as the crop from the 645 image. So when a person uses this practice as proof of F4 is equal to F4 all they have done is shown that yes they have the same DOF only because they have been using the same final format size of 1.06mmx0.76mm with surface area of 0.81mm2( same portion of the image circle)

It has nothing to do with the image circle of the lens. It doesn't matter if the 50mm lens is for a Q or for 645 . And I don't know what fragment of an image was 1.06mmx0.76mm

That is the final size of the format that would have capture that image.

When people show a crop from a big image and whole of a small image made with the same focal length and aperture and say "look they are the same" they are: they must be otherwise the lens would be doing something different to the light depending on what was behind it. But that is like saying the pixels that represent the shape of this letter > O < is the same whether you look at normal resolution or whether you magnify the screen 10 times, but it looks Circular, and black on white , right ? But if you magnify it you get this.

I will start from the beginning

The First image taken with the 645 is basically there to show what a 645 crop of the image circle using a 55mm F4 looks like or another way to put it, it’s the negative. And from that negative I cut out a full frame negative, APSC negative, and a Q negative. This way we can see what is happening as we use different formats.

In the second part I took those negatives above and again cropped them all again to the same size of negative the Q would have captured. So of course they will all be the same size of negative. What I am trying to debunk is individual that use this kind of cropping between formats as evidence that a 55mm F/4 lens has the same DOF regardless the format. My intention was to show that all they have done is created equal size negatives using 4 different format sizes from the same image circle, so of course they will have the same DOF.

An example of this is a person using a Apsc 55mm F/4 image cropping it to the same FOV as what a Q 55mmF/4 would capture. Then they would use Q55mmF/4 image scaling it the size of that Apsc image. They would then put this up as side by side comparison to prove that Apsc 55mmF/4 has the same DOF as a Q 55mm F/4. My intent was to show all they done was convert the Apsc into lower resolution Q format camera and that they are not truly comparing APSC to the Q.

I hope this helps out

Think of film. I shoot with with a 10"x8" plate camera, (254mm x 208mm) and something a certain amount out of focus turns into a circle 0.07mm wide that's 3/10,000th of the width. Too small to see . The I crop down to a Q sensor-size at 7.4mm X 5.6mm that same circle size is 1/100th of the image width, plenty big enough to see. The same thing has different APPARANT sharpness depending on the magnification.

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Ian Stuart Forsyth
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Re: Cropping from within a format (101)
In reply to moving_comfort, 10 months ago

moving_comfort wrote:

James O'Neill wrote:

Ian Stuart Forsyth wrote:

James O'Neill wrote:

Ian Stuart Forsyth wrote:

As you can see that they share the same FOV and DOF now why is this? (bear with me if you Know)

They are all the same because you have not achieved the same FoV by changing focal length but by cropping, In one you have cropped once and the rest you have cropped twice.

The test was not to change the FOV by FL see below

The smaller the fragment of the image you zoom in to, the easier it is to see what is out of focus. The cereal is just as out of focus in the whole frame as it is in the cropped-down-to-Q frame, but at such you can't see it in the whole frame.

This does not prove F4 on any of the 4 format sizes is the same but rather that if we crop an image from format and compare it to another format at the same FOV that the DOF will be the same only because the share the size portion of the project image circle from the 55mm F4 lens (same format size). So at the end of the day we still have F2.8 is not equal to F2.8 across formats.

That's not the clearest phrasing in the history of English. A small image from the camera - whether it started small or was cropped from a bigger one - has to be magnified more than large one to fill the same size sheet of photographic paper or computer screen. As you magnify what was in the D.o.F zone because you couldn't see it was slightly out of focus is revealed to be blurred.

D.o.F isn't some magical "What's in is perfectly focused" zone , but "What's in is so slightly out of focus you don't notice". The same focus "error" with the same lens and same aperture will produce the same distance of blurring on the film or sensor: 0.02 mm of blur is harder to see on a 33x44mm image than a 3x4 mm one. Hence all d.o.f. calculations use a circle of confusion size which depends on image size : and that is image size after all cropping has been done.

The test showed this.

Taking images with 4 different format sizes and cropping them all to the same FOV

You didn't though. You took an image and cropped it to 4 sizes. Then you cropped the large size a second time, so cropped the same image down to the same image in 4 different ways.

viewing them at the same magnification is a practice that many use to show that F4 is the same as F4 across format. But this is not correct and will not prove that F 4 is the same. Here’s why, the size of the final viewed image is in fact another format size with a different FOV.

You can argue it both ways - if you magnify a section of the image that has a smaller FoV but it is the magnification - or more accurately the change in workable Circle of Confusion size - that has the impact on DoF. If you change the FoV by changing image size and not focal length , it reduces the circle size.

By cropping the 645 to this FOV you are using another format,…. And cropping the Q to the same FOV you are using the same format size as the crop from the 645 image. So when a person uses this practice as proof of F4 is equal to F4 all they have done is shown that yes they have the same DOF only because they have been using the same final format size of 1.06mmx0.76mm with surface area of 0.81mm2( same portion of the image circle)

It has nothing to do with the image circle of the lens. It doesn't matter if the 50mm lens is for a Q or for 645 . And I don't know what fragment of an image was 1.06mmx0.76mm

When people show a crop from a big image and whole of a small image made with the same focal length and aperture and say "look they are the same" they are: they must be otherwise the lens would be doing something different to the light depending on what was behind it. But that is like saying the pixels that represent the shape of this letter > O < is the same whether you look at normal resolution or whether you magnify the screen 10 times, but it looks Circular, and black on white , right ? But if you magnify it you get this.

Think of film. I shoot with with a 10"x8" plate camera, (254mm x 208mm) and something a certain amount out of focus turns into a circle 0.07mm wide that's 3/10,000th of the width. Too small to see . The I crop down to a Q sensor-size at 7.4mm X 5.6mm that same circle size is 1/100th of the image width, plenty big enough to see. The same thing has different APPARANT sharpness depending on the magnification.

James, I don't want to speak for Ian but I think you're misinterpreting what he was trying to show.

Basically, I think he was just trying to show how if you crop an image, and then display the crop magnified (ie, at the same or 'regular' display sizes) the DOF changes - more of the image is 'in focus' after the crop and magnification. It's the act of magnification that does this, nothing changes internally in the image.

It's exactly the same reason why a native FF shot has a different DOF (for the same FOV, aperture and distance) as a native aps-c shot taken from the same position - but if you crop the FF shot to match the aps-c FOV and then follow through by magnifying that crop to the same display size, the DOF is now the same as the aps-c shot - when before it was different.

Yes thank you

This is what (I think) Ian was tying to show in order to convince awaldram, who's now claiming he never denied it. I don't think Ian's crop examples there were the best idea, because awaldram thought they were meant to show him that the "DOF is always the same".

Anyway, that's my take on this sub-thread

.

.

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awaldram
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Re: U R Slippery II
In reply to moving_comfort, 10 months ago

moving_comfort wrote:

By the way, can you explain how you changed your story on this answer you gave below?

.

You changed your story on that, which represents progress - what made you change?

As I said earlier I'm bored with this now but have to pull you up on that miss quoting

you said

you I used to hold the position it does not (change DoF when displayed at same size)

I did do and always will do , Ian posted examples that prove it , I posted examples that prove it, and both James and myself posted algorithms that prove it.

No amount of trying to make something different will alter that.!

DoF is relative to magnification.

Equivalence as defined by you ,Ian and Lumo is just wrong and misleading.

A lens does not change any of it characteristics ever !

Altering Focal length aperture etc as you change format to produce a similar image and then stating it is equivalent is based on the idea the larger format is superior to the smaller.

Often it is not often the smaller format has higher pixel density , lower relative noise, more efficient pixels or better DR this then completely breaks you equivalence.

take a 6mp FF and a k5 run you 'equivalent ideas to create ti 'equivalent pictures.

Only they wont be the FF will be noisey and grainy

How come ?

take these to images as I asked before both shot from an external light meter reading why are they the same exposure ?

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

do you see the error in your thinking yet?

You can approximate DoF or FoV but to then assume those approximations are some kind of equivalent across all parameters leads to your La La worlds and is easily disproved as the images below.

.

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awaldram
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Re: DOF and Cropping take 2
In reply to Mark Ransom, 10 months ago

Mark Ransom wrote:

I think your calculations for motion blur are off. The motion blur is caused by the motion of the camera, which is independent of sensor size - if the sensor is 1.5x smaller then the blur must also be 1.5x smaller to maintain the same visibility across the frame. So if you need 1/400 for FF, you'll also need 1/400 for APS-C and 1/400 for the Q.

Anti-shake technology may mean the 1/FL guideline can be loosened a bit, but again that should be the same for all sensor sizes.

Yeah , your to kind I was talking rubbish of cause camera blur remains constant due to FoV scaling inversely to sensor size.

I was thinking about this and having a play it doesn’t quite work and I can't see why.?

I can hold a 40mm lens easily without IS on a 5.5 crop sensor @1/3 of a second which is ridiculous for 220mm FoV

I can't do the same with 150mm on aps-c

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awaldram
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Re: Awaldram
In reply to moving_comfort, 10 months ago

moving_comfort wrote:

Great Bustard wrote:

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens). However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor:

25mm f/1.4 on mFT (4/3) is equivalent to 31mm f/1.8 on 1.6x (Canon APS-C), 33mm f/1.9 on 1.5x (APS-C for everyone else), and 50mm f/2.8 on FF (FX), where "equivalent to" means:

  • The photos all have the same diagonal angle of view (25mm x 2 = 31mm x 1.6 = 33mm x 1.5 = 50mm) and aperture diameter (25mm / 1.4 = 31mm / 1.8 = 33mm / 1.9 = 50mm / 2.8 = 18mm).
  • The photos all have the same perspective when taken from the same position.
  • The photos all have the same DOF (as well as diffraction softening) when they are taken from the same position with the same focal point and have the same display size.
  • The photos all have the same motion blur for the same shutter speed (regardless of pixel count).
  • The same total amount of light falls on the sensor for the same DOF and shutter speed.
  • The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).
  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.
  • The same total light will result in the same noise for equally efficient sensors (regardless of pixel count and regardless of the ISO setting).
  • If the 25mm lens at f/1.4 has twice the resolution as the 50mm lens at f/2.8 on FF, 1.33x the resolution of the 33mm lens at f/1.8 on 1.5x, and 1.25x the resolution of the 31mm at f/1.8 on 1.6x, the sensors have the same pixel count and same AA filter strength, then all systems will also resolve the same detail.
  • Other elements of IQ, such as bokeh, color, distortion, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

.

So Awaldram, you've called Falk's paper a 'fallacy', although I doubt you'd really think the whole thing could be a fallacy. I'm left with not knowing what parts of it you agree with or not. So let's move to the above - what do you think is false or 'crackpot' to use your word, in the above?

You seem to not agree with:

  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.

Based on what you said here (in reference to Ian stating a correct equivalent relationship he layed out which would have required the FF image to use ISO 225 to match the aps-c ISO 100 with the same total amount of light) :

...Ian/MC said FF required iso225 to match iso100 aps-c - wrong

...On another subject you keep saying iso100 on aps-c = iso 225 on FF

...Again your doing some kind of weird 'equivalence' to push some FF agenda

And you seem to disagree with the following: "...However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor"

Based on what you said here:

...Ian/MC said DoF is a function of sensor size - wrong

...I said an f2.8 lens is an f2.8 lens on any sensor - Check Proved

...Ian/MC stated a lens alters it behaviour and f2.8 is not the same but depends on sensor size - yet again wrong.

So, anything else you disagree with in the above (or can you be more specific about what you disgaree with in Falk's paper? )

Do you read what you quote??

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens).

Yet another source agrees with me !

You see what you miss is the qualifiers which then leads you to make assumptions based on insufficient data.

In your quote iso100- iso225

the premise Ian is taking is that to match DoF you need to shut the aperture down this intern means you need to up iso to maintain the exposure solution.

Now it seems good stuff ? ....But you could also crop the same image from the same lens across format and achieve the exact same result but without altering exposure, (because an f2.8 lens is always an f2.8 lens !!!!)

Yet you alter multiple factors and then use them singularly to 'prove' your fallacy.

As to Falconeyes white paper I said it was unproven and thefore made up, It's his view and like most things has stuff I agree with and stuff I don't but if unproven its all conjecture.

Nothing wrong with that , but you then are using it as 'the bible on equivalents' is just funny ... an unproven source is your mantra .

Given the evidence above it obvious to all  the 'Equivalent ' model your pushing as some kind of new photography rule is wrong and broken.

It only works for a very small subset of conditions and only if you assume FF is superior to anything else.

Something we all know all those proposing it are indeed FF Zealots.

.

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Re: Equivalence.
In reply to Great Bustard, 10 months ago

Great Bustard wrote:

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens). However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor:

25mm f/1.4 on mFT (4/3) is equivalent to 31mm f/1.8 on 1.6x (Canon APS-C), 33mm f/1.9 on 1.5x (APS-C for everyone else), and 50mm f/2.8 on FF (FX), where "equivalent to" means:

  • The photos all have the same diagonal angle of view (25mm x 2 = 31mm x 1.6 = 33mm x 1.5 = 50mm) and aperture diameter (25mm / 1.4 = 31mm / 1.8 = 33mm / 1.9 = 50mm / 2.8 = 18mm).
  • The photos all have the same perspective when taken from the same position.
  • The photos all have the same DOF (as well as diffraction softening) when they are taken from the same position with the same focal point and have the same display size.
  • The photos all have the same motion blur for the same shutter speed (regardless of pixel count).
  • The same total amount of light falls on the sensor for the same DOF and shutter speed.
  • The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).
  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness of the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.
  • The same total light will result in the same noise for equally efficient sensors (regardless of pixel count and regardless of the ISO setting).
  • If the 25mm lens at f/1.4 has twice the resolution as the 50mm lens at f/2.8 on FF, 1.33x the resolution of the 33mm lens at f/1.8 on 1.5x, and 1.25x the resolution of the 31mm at f/1.8 on 1.6x, the sensors have the same pixel count and same AA filter strength, then all systems will also resolve the same detail.
  • Other elements of IQ, such as bokeh, color, distortion, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

Good work agree 100% with this , wish I'd written it

Covers off the areas that break the 'equivalence' model nicely.

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Re: U R Slippery II
In reply to awaldram, 10 months ago

awaldram wrote:

moving_comfort wrote:

By the way, can you explain how you changed your story on this answer you gave below?

.

You changed your story on that, which represents progress - what made you change?

As I said earlier I'm bored with this now but have to pull you up on that miss quoting

you said

you I used to hold the position it does not (change DoF when displayed at same size)

I did do and always will do , Ian posted examples that prove it , I posted examples that prove it, and both James and myself posted algorithms that prove it.

No amount of trying to make something different will alter that.!

DoF is relative to magnification.

Equivalence as defined by you ,Ian and Lumo is just wrong and misleading.

A lens does not change any of it characteristics ever !

Altering Focal length aperture etc as you change format to produce a similar image and then stating it is equivalent is based on the idea the larger format is superior to the smaller.

Often it is not often the smaller format has higher pixel density , lower relative noise, more efficient pixels or better DR this then completely breaks you equivalence.

take a 6mp FF and a k5 run you 'equivalent ideas to create ti 'equivalent pictures.

Only they wont be the FF will be noisey and grainy

How come ?

take these to images as I asked before both shot from an external light meter reading why are

A very simple question, at the single photocell level why does the K 5 pixel show up as bright as a Q pixel when both are shot at the same shutter speed, Fstop and iso when viewed on the back of the camera. We know that the k5 photocell is several times large than the Q’s giving the k5 photocell more light whereas the Q’s is smaller and would receive less light. This should make k5 image way brighter as it has captured more light right?

  1. The photocell of the Q is several times more efficient at gather light so it would show up as bright
  2. That all sensor have a gain applied to them to bring them up to the same brightness to meet the standard iso rating and make up for the smaller photon count of a smaller photocell
  3. Physics is out the window
  4. Size of the photocell has nothing to do with how much light is gathered

they the same exposure ?

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

do you see the error in your thinking yet?

You can approximate DoF or FoV but to then assume those approximations are some kind of equivalent across all parameters leads to your La La worlds and is easily disproved as the images below.

.

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Re: Equivalence.
In reply to awaldram, 10 months ago

awaldram wrote:

Great Bustard wrote:

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

This nicely cover off everything in this thread

  • Equivalence is only relevant when comparing different formats. For example, if we are comparing the performance of a 50mm lens designed for FF to a 50mm lens designed for APS-C or mFT (4/3), both lenses being used on the same camera, Equivalence does not come into play.
  • Neither the focal length nor the f-ratio of a lens change as a function of format: 50mm = 50mm and f/2 = f/2 regardless of the format the lens is used on.
  • The effect of the focal length and f-ratio of a lens, however, do change as a function of format.
  • The DOF is the same for all systems for a given perspective, framing, aperture diameter, and display display size. For the same aperture diameter and shutter speed, the same total amount of light will fall on the sensor for all systems, resulting in a lower exposure for larger sensors systems (same total amount of light distributed over a larger area results in a lower exposure, since exposure is the density of the light falling on the sensors).
  • The same total amount of light falling on the sensor will result in the same noise for equally efficient sensors, regardless of pixel size or the ISO setting. Typically, sensors of the same generation are rather close in efficiency, but there are most certainly exceptions.
  • Larger formats do not necessarily have a more shallow DOF than smaller formats. Larger formats have the option of a more shallow DOF than smaller formats for a given perspective and framing when using a lens that has a larger aperture diameter, as the lenses for larger formats usually, but not always, have larger aperture diameters for a given AOV. However, people using Auto, P, or Tv modes on the camera will likely find that the larger format camera will choose a wider aperture in many situations, resulting in a more shallow DOF. In addition, many choose to use a wider aperture (resulting in a more shallow DOF) to get more light on the sensor and thus less noise.
  • Equivalence says nothing about shallow DOF being superior to deep DOF, as this is entirely subjective.
  • The resolved detail is a function of the lens, the AA filter, the sensor, and the processing (RAW vs default jpg, for example). A sharper lens (greater lp/mm) on a smaller sensor will not necessarily resolve more than a less sharp lens on a larger sensor. Instead, we need to compare the resolutions in lw/ph, as DPR does with their MTF-50 tests (discussed in more detail here). Furthermore, the resolved detail is also a function of the number of pixels on the sensor (discussed in more detail here), and all systems suffer the same amount of diffraction softening equally at the same DOF, although the system that began with more detail will retain more detail (although the advantage asymptotically vanishes as the DOF deepens -- discussed in more detail here).
  • Equivalence makes no claims whatsoever about which system is superior to another system, especially given that there are so many aspects about systems that Equivalence does not address. For example, in terms of IQ, Equivalence says nothing about bokeh, moiré, distortion, color, etc., and in terms of operation, Equivalence says nothing about AF, build, features, etc. In fact, Equivalence can even work against larger sensor systems by denying them their "noise advantage" when they need to match both the DOF and shutter speed of smaller sensor systems.
  • However, Equivalence does make the argument that it makes no sense to artificially handicap one system or the other by requiring identical settings for a comparison, when identical settings result in different effects on different systems.

This point

The reason that smaller sensors are more noisy than larger sensors is not because they are less efficient, but because less light falls on them for a given exposure. If the larger sensor is more efficient than the smaller sensor, then the noise gap will widen, if the smaller sensor is more efficient, the noise gap will shrink.

I don't think tells the whole story , because we use ISO to define the sensitivity of the sensor then surely for a give ISO every sensor will be identical.?

So my view would be

The reason smaller sensors are more noisy than larger sensors is because less light fall on them (light density) they therefore have higher internal gain per ISO to compensate.

This gain increases the noise for any given exposure solution.

As per Nikon USA

How much light is needed is determined by the sensitivity of the medium used. That was as true for glass plates as it is for film and now digital sensors. Over the years that sensitivity has been expressed in various ways, most recently as ASA and now ISO.

So for any sensor size ISO 100 will deliver the same exposure (and why external light-meters work across formats)

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Re: U R Slippery II
In reply to Ian Stuart Forsyth, 10 months ago

Ian Stuart Forsyth wrote:

awaldram wrote:

moving_comfort wrote:

By the way, can you explain how you changed your story on this answer you gave below?

.

You changed your story on that, which represents progress - what made you change?

As I said earlier I'm bored with this now but have to pull you up on that miss quoting

you said

you I used to hold the position it does not (change DoF when displayed at same size)

I did do and always will do , Ian posted examples that prove it , I posted examples that prove it, and both James and myself posted algorithms that prove it.

No amount of trying to make something different will alter that.!

DoF is relative to magnification.

Equivalence as defined by you ,Ian and Lumo is just wrong and misleading.

A lens does not change any of it characteristics ever !

Altering Focal length aperture etc as you change format to produce a similar image and then stating it is equivalent is based on the idea the larger format is superior to the smaller.

Often it is not often the smaller format has higher pixel density , lower relative noise, more efficient pixels or better DR this then completely breaks you equivalence.

take a 6mp FF and a k5 run you 'equivalent ideas to create ti 'equivalent pictures.

Only they wont be the FF will be noisey and grainy

How come ?

take these to images as I asked before both shot from an external light meter reading why are

A very simple question, at the single photocell level why does the K 5 pixel show up as bright as a Q pixel when both are shot at the same shutter speed, Fstop and iso when viewed on the back of the camera. We know that the k5 photocell is several times large than the Q’s giving the k5 photocell more light whereas the Q’s is smaller and would receive less light. This should make k5 image way brighter as it has captured more light right?

  1. The photocell of the Q is several times more efficient at gather light so it would show up as bright
  2. That all sensor have a gain applied to them to bring them up to the same brightness to meet the standard iso rating and make up for the smaller photon count of a smaller photocell
  3. Physics is out the window
  4. Size of the photocell has nothing to do with how much light is gathered

That is simple we have a standard that define how a film/sensor/plate will react to the amount of light it receives.

It called ISO and is constant for any given luminosity cameras are calibrated to it and DXO measure how much those manufacturers egg the cake (erm hello Nikon)

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

What will alter is noise levels as the more efficient a sensor at capturing light be that  through size or well the lower gain it will need to 'calibrate' to the ISO scale.

As this calibration is outside user control you cannot alter it all you can do is prove it existence by showing the exposure is constant across sensor sizes for the same lens and aperture used (at 18% grey)

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Re: U R Slippery II
In reply to awaldram, 10 months ago

awaldram wrote:

moving_comfort wrote:

By the way, can you explain how you changed your story on this answer you gave below?

.

You changed your story on that, which represents progress - what made you change?

As I said earlier I'm bored with this now but have to pull you up on that miss quoting

you said

you I used to hold the position it does not (change DoF when displayed at same size)

I did do and always will do , Ian posted examples that prove it , I posted examples that prove it, and both James and myself posted algorithms that prove it.

No amount of trying to make something different will alter that.!

DoF is relative to magnification.

Equivalence as defined by you ,Ian and Lumo is just wrong and misleading.

A lens does not change any of it characteristics ever !

Altering Focal length aperture etc as you change format to produce a similar image and then stating it is equivalent is based on the idea the larger format is superior to the smaller.

Often it is not often the smaller format has higher pixel density , lower relative noise, more efficient pixels or better DR this then completely breaks you equivalence.

take a 6mp FF and a k5 run you 'equivalent ideas to create ti 'equivalent pictures.

Only they wont be the FF will be noisey and grainy

How come ?

take these to images as I asked before both shot from an external light meter reading why are they the same exposure ?

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

You just proved why it shouldn't be under exposed with your answer here kind of

http://www.dpreview.com/forums/post/53107658

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

the Q at F/2.8 1/80 iso 800 needs more gain as it has captured 13 times less total light than K3 at F/2.8  1/80 iso 800 because of the sensor size difference

We can reduce the AP on the K3 to F/10 raise the iso 3000 and then it would gather around the same total light as the Q F/2.8 1/80 iso 800

Or another way to look at it the Q iso 800 = k3 iso 3000

I could only find the Q7 to compare to the K3

do you see the error in your thinking yet?

You can approximate DoF or FoV but to then assume those approximations are some kind of equivalent across all parameters leads to your La La worlds and is easily disproved as the images below.

.

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Re: Equivalence.
In reply to awaldram, 10 months ago

awaldram wrote:

awaldram wrote:

Great Bustard wrote:

Here we are:

http://www.josephjamesphotography.com/equivalence/#quick

This nicely cover off everything in this thread

  • Equivalence is only relevant when comparing different formats. For example, if we are comparing the performance of a 50mm lens designed for FF to a 50mm lens designed for APS-C or mFT (4/3), both lenses being used on the same camera, Equivalence does not come into play.
  • Neither the focal length nor the f-ratio of a lens change as a function of format: 50mm = 50mm and f/2 = f/2 regardless of the format the lens is used on.
  • The effect of the focal length and f-ratio of a lens, however, do change as a function of format.
  • The DOF is the same for all systems for a given perspective, framing, aperture diameter, and display display size. For the same aperture diameter and shutter speed, the same total amount of light will fall on the sensor for all systems, resulting in a lower exposure for larger sensors systems (same total amount of light distributed over a larger area results in a lower exposure, since exposure is the density of the light falling on the sensors).
  • The same total amount of light falling on the sensor will result in the same noise for equally efficient sensors, regardless of pixel size or the ISO setting. Typically, sensors of the same generation are rather close in efficiency, but there are most certainly exceptions.
  • Larger formats do not necessarily have a more shallow DOF than smaller formats. Larger formats have the option of a more shallow DOF than smaller formats for a given perspective and framing when using a lens that has a larger aperture diameter, as the lenses for larger formats usually, but not always, have larger aperture diameters for a given AOV. However, people using Auto, P, or Tv modes on the camera will likely find that the larger format camera will choose a wider aperture in many situations, resulting in a more shallow DOF. In addition, many choose to use a wider aperture (resulting in a more shallow DOF) to get more light on the sensor and thus less noise.
  • Equivalence says nothing about shallow DOF being superior to deep DOF, as this is entirely subjective.
  • The resolved detail is a function of the lens, the AA filter, the sensor, and the processing (RAW vs default jpg, for example). A sharper lens (greater lp/mm) on a smaller sensor will not necessarily resolve more than a less sharp lens on a larger sensor. Instead, we need to compare the resolutions in lw/ph, as DPR does with their MTF-50 tests (discussed in more detail here). Furthermore, the resolved detail is also a function of the number of pixels on the sensor (discussed in more detail here), and all systems suffer the same amount of diffraction softening equally at the same DOF, although the system that began with more detail will retain more detail (although the advantage asymptotically vanishes as the DOF deepens -- discussed in more detail here).
  • Equivalence makes no claims whatsoever about which system is superior to another system, especially given that there are so many aspects about systems that Equivalence does not address. For example, in terms of IQ, Equivalence says nothing about bokeh, moiré, distortion, color, etc., and in terms of operation, Equivalence says nothing about AF, build, features, etc. In fact, Equivalence can even work against larger sensor systems by denying them their "noise advantage" when they need to match both the DOF and shutter speed of smaller sensor systems.
  • However, Equivalence does make the argument that it makes no sense to artificially handicap one system or the other by requiring identical settings for a comparison, when identical settings result in different effects on different systems.

This point

The reason that smaller sensors are more noisy than larger sensors is not because they are less efficient, but because less light falls on them for a given exposure. If the larger sensor is more efficient than the smaller sensor, then the noise gap will widen, if the smaller sensor is more efficient, the noise gap will shrink.

I don't think tells the whole story , because we use ISO to define the sensitivity of the sensor then surely for a give ISO every sensor will be identical.?

So my view would be

The reason smaller sensors are more noisy than larger sensors is because less light fall on them (light density) they therefore have higher internal gain per ISO to compensate.

This gain increases the noise for any given exposure solution.

This is why Iso 100 on dx is the same as iso 225 on FF Full Frame needs less gain to start with

what happens if FF shoots at Iso 100 and DX shoots at iso 100 for the same exposure?

As per Nikon USA

How much light is needed is determined by the sensitivity of the medium used. That was as true for glass plates as it is for film and now digital sensors. Over the years that sensitivity has been expressed in various ways, most recently as ASA and now ISO.

So for any sensor size ISO 100 will deliver the same exposure (and why external light-meters work across formats)

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Re: U R Slippery II
In reply to Ian Stuart Forsyth, 10 months ago

Ian Stuart Forsyth wrote:

awaldram wrote:

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

You just proved why it shouldn't be under exposed with your answer here kind of

http://www.dpreview.com/forums/post/53107658

Yep but thats obvious iso 100 = iso 100 on any format , f2.8 = f.28 , 1/180 = 1/180 format is irrelevant there a constant.

Hence my bewilderment about your claims to the contrary.

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

the Q at F/2.8 1/80 iso 800 needs more gain as it has captured 13 times less total light than K3 at F/2.8 1/80 iso 800 because of the sensor size difference

Not sure what you trying to say. the Q will produce more noise at iso 800 than the k3 because it requires more internal gain to match sensitivity but both will have the same light sensitivity at iso800.

We can reduce the AP on the K3 to F/10 raise the iso 3000 and then it would gather around the same total light as the Q F/2.8 1/80 iso 800

Why would you do this.?

Or another way to look at it the Q iso 800 = k3 iso 3000

No chance ISo is a standard its calibrated and set on every camera ever made , without it photography would not exist as it does today. Every camera would require custom algorithms for every exposure

Q iso800 = k3 iso 800 = 645d iso80 = glass plate camera iso800 = hubble telescope iso800.

As the image I posted proved setting the same aperture , the same shutter and the same iso results in the same exposure across formats.

Not sure what your showing maybe that the k3 noise at 3200 is similar to Q7 @800?

I could only find the Q7 to compare to the K3

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justin23
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Re: U R Slippery II
In reply to awaldram, 10 months ago

awaldram wrote:

Ian Stuart Forsyth wrote:

awaldram wrote:

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

You just proved why it shouldn't be under exposed with your answer here kind of

http://www.dpreview.com/forums/post/53107658

Yep but thats obvious iso 100 = iso 100 on any format , f2.8 = f.28 , 1/180 = 1/180 format is irrelevant there a constant.

Hence my bewilderment about your claims to the contrary.

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

the Q at F/2.8 1/80 iso 800 needs more gain as it has captured 13 times less total light than K3 at F/2.8 1/80 iso 800 because of the sensor size difference

Not sure what you trying to say. the Q will produce more noise at iso 800 than the k3 because it requires more internal gain to match sensitivity but both will have the same light sensitivity at iso800.

We can reduce the AP on the K3 to F/10 raise the iso 3000 and then it would gather around the same total light as the Q F/2.8 1/80 iso 800

Why would you do this.?

Or another way to look at it the Q iso 800 = k3 iso 3000

No chance ISo is a standard its calibrated and set on every camera ever made , without it photography would not exist as it does today. Every camera would require custom algorithms for every exposure

Q iso800 = k3 iso 800 = 645d iso80 = glass plate camera iso800 = hubble telescope iso800.

As the image I posted proved setting the same aperture , the same shutter and the same iso results in the same exposure across formats.

Not sure what your showing maybe that the k3 noise at 3200 is similar to Q7 @800?

I could only find the Q7 to compare to the K3

What you are really comparing is relative noise. Yes ISO 800 on smaller sensors is likely to have more noise and may have similar noise to a K-3 ISO 3200, but if you take a photo on a K3 at say iso 800 f8 and 1/250 you will use the same settings on a Q for the same exposure. In fact the sensor pitch is more important, because on a per area basis they'll all get the same amount of light, its just how well the sensor can capture it, a bigger sensor with the same sensor pitch as a smaller sensor captures the same amount of light per area and should be close on noise.

However the smaller sensor tend to have a much higher pitch and thus the noise is higher.  What amuses me most is the only reason we don't have FF sensors with such a high pitch is cost and the smallish market.

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Ian Stuart Forsyth
Senior MemberPosts: 1,877Gear list
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Re: U R Slippery II
In reply to awaldram, 10 months ago

awaldram wrote:

Ian Stuart Forsyth wrote:

awaldram wrote:

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

You just proved why it shouldn't be under exposed with your answer here kind of

http://www.dpreview.com/forums/post/53107658

Yep but thats obvious iso 100 = iso 100 on any format , f2.8 = f.28 , 1/180 = 1/180 format is irrelevant there a constant.

Hence my bewilderment about your claims to the contrary.

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

the Q at F/2.8 1/80 iso 800 needs more gain as it has captured 13 times less total light than K3 at F/2.8 1/80 iso 800 because of the sensor size difference

Not sure what you trying to say. the Q will produce more noise at iso 800 than the k3 because it requires more internal gain to match sensitivity but both will have the same light sensitivity at iso800.

yes

We can reduce the AP on the K3 to F/10 raise the iso 3000 and then it would gather around the same total light as the Q F/2.8 1/80 iso 800

Why would you do this.?

If you required the K3 to have the same DOF as the Q at F2.8

Or think about this if you don't need F10 open it up to F2.8 and shoot the k3 at iso 3200 with a shutter speed 13 times faster and still capture the same total light as the Q F2.8 iso 800 1/80

Or another way to look at it the Q iso 800 = k3 iso 3000

No chance ISo is a standard its calibrated and set on every camera ever made , without it photography would not exist as it does today. Every camera would require custom algorithms for every exposure

Some  sensors photocells collect 10 and other can only collect 2 for that given exposure so each series of  sensor will need a  different gain to meet the iso standard ( kind of like a pre gain)

Q iso800 = k3 iso 800 = 645d iso80 = glass plate camera iso800 = hubble telescope iso800.

As the image I posted proved setting the same aperture , the same shutter and the same iso results in the same exposure across formats.

but different amount of total light collected because of sensor size and different amount of pre gain to bring them up to the iso standard ( think of it this way more total light gathered less pre gain need)

But the Q needs a pre gain 13 times higher to meet that iso standard

this is why the K3@ iso 3200 looks like the Q at iso 800

Not sure what your showing maybe that the k3 noise at 3200 is similar to Q7 @800?

yes same total light same total noise

I could only find the Q7 to compare to the K3

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The Camera is only a tool, photography is deciding how to use it.
The hardest part about capturing wildlife is not the photographing portion; it’s getting them to sign a model release

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falconeyes
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Re: Awaldram
In reply to awaldram, 10 months ago

awaldram wrote

As to Falconeyes white paper I said it was unproven and thefore made up, It's his view and like most things has stuff I agree with and stuff I don't but if unproven its all conjecture.

I just see this now. Didn't know people exist who consider it a conjecture. However as I wrote in the white paper, I went through the math to proove every statement I make in the paper. So, it isn't a conjecture. And as it is easy to proove, just textbook exercise level, I never saw a point to bother readers with the math. They either understand (and are easily able to replicate) the math or they don't. Moreover, I had extensive private communications about it and its math was never challenged (equations need a minor modification if you drop the assumption of small magnification).

I really think the problem is one of language. E.g., terms "exposure", "illuminance", "luminance" and "luminous flux" are sources of confusion (I don't exclude my white paper here because I didn't anticipate this problem).

Esp. exposure should be avoided or clearly defined, e.g., if it represents an EV or a LV.

Another point is what "equivalent" means: It does not mean that, e.g., a change in sensor size or a crop changes a lens' focal length. It does mean that, for any given camera 0 with settings exposure time t0, focal length f0, aperture n0, sensitivity iso0, and sensor size s0, another camera 1 does exist (with settings t1, f1, n1, iso1, s1) where t0=t1 but all other parameters different. And where both camera 0 and 1 produce indistiguishable images, making both parameter sets "equivalent", in the mathematical meaning of equivalence classes. And as s0 and s1 differ, this may then be an ideal starting point in a reasoning about the impact of sensor size on produced images.

Regarding this thread, I wonder what is discussed actually. There seems to be a basic consensus. I think what remains is different use of words and assumptions about possible hidden agenda of some participants. Which is funny as the underlying facts are too simple to spend more than, say 3 posts

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Falk Lumo

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