"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions
amtberg
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You are quite correct!
In reply to walkaround, Apr 28, 2013

I have no idea why people get so confused by this.  Factoring in the crop factor, lenses of equal maximum aperture will produce the same framing and exposure across systems.  Only depth of field will differ.  Thus the lenses are equivalent in one respect and not equivalent in another.

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tko
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Re: What you have demonstrated is not what they mean by equivalence
In reply to JosephScha, Apr 28, 2013

1. Equivalence means what they say it means. What is equivalent is perspective (you got that right), framing, depth of field, shutter speed and displayed size. Nothing more.

And noise. You forgot noise. Shutter speed is not included. That's an input variable. Display size is a constant. Noise, DOF, and framing. Only three.

2. It is not about equivalent exposure (light per unit area), it is about total light reaching the sensor. The goal is to measure efficiency of different sensors.

It has nothing to do with efficiency of sensor as the term is commonly used (photons in, electrons out.) It assumes are sensors are approximately equal.

In your pictures you made exposure the same, and (therefore) depth of field was different. That is meaningful, maybe even more intuitive, but it is not what the people you are aiming at mean by equivalence. Once I understood that I was more happy to let them mean whatever they want. I am not yet convinced that thinking that way will be very useful, but it's not totally bogus. They just defined equivalence as they wanted to serve that particular purpose.

Equivalence only has one definition. What settings should you adjust to make the images from two differently size sensors look as much as possible the same. That is where the name--equivalence--comes from.

If you want to introduce your own theory, give it a new name.

While I'm writing:
3. Exposure only means total light hitting the sensor. Everything after that is "brightening". I a really like that, the only problem is general usage. Even the top slider in ACR is labelled "exposure" when it's clearly iso adjust, or brightening.

Actually, I agree with you, but one must be careful in renaming industry terms -- even if they are wrong. For example, most people would think of changing ISO as adjusting exposure, but under your definition it doesn't. The exposure triangle would collapse into the exposure line. Something about letting sleeping dogs lie. The problem is ISO no longer measures sensor light sensitivity. It is how much gain there is afterwards.

4. 4/3 needs two stops more open than FF to have same total light on the sensor.

Correct.

I'd better stop here. There is tons more to read, some of it quite mathematical, to see where the definition they use for "equivalence" came from and how it can be useful. My intent here is just to ask you to allow them their definition, and if it's not what you care about that is OK.
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js

Mathematics is only useful when you have the basic concepts and big picture down. Equivalence is so simple you can derive all the formulas in a few minutes, so simple you can state the premise in one sentence.

What camera settings make the images look most similar in terms of noise, framing, and DOF?

I find pages of math are frequently used to obscure simple concepts. You don't need complicated math here!

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amtberg
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Re: What you have demonstrated is not what they mean by equivalence
In reply to tko, Apr 28, 2013

I think you are discounting the fact that shutter speed often does cause images to look different.  You aren't accounting for motion blur.

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DigiMatt
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to walkaround, Apr 28, 2013

walkaround wrote:

"Total light on the sensor" is a meaningless concept.

The only thing you have demonstrated is your ignorance.

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Ricardo Maia
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to DigiMatt, Apr 28, 2013

DigiMatt wrote:

walkaround wrote:

"Total light on the sensor" is a meaningless concept.

The only thing you have demonstrated is your ignorance.

Got to love these spitting posts without any explanation whatsoever...

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DigiMatt
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to Ricardo Maia, Apr 28, 2013

Ricardo Maia wrote:

DigiMatt wrote:

walkaround wrote:

"Total light on the sensor" is a meaningless concept.

The only thing you have demonstrated is your ignorance.

Got to love these spitting posts without any explanation whatsoever...

What more do you want? Equivalence has been explained about 500 times already in the DPR forums. Do you need it repeated 500 more times?

Just read and understand this. I think it will help.

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Great Bustard
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Re: An answer:
In reply to Olymore, Apr 28, 2013

Olymore wrote:

GB, Thanks for that.

De nada.

I was thinking of a situation where the sensors were identical except for size (so effectively the M43 sensor would be a crop of the FF one), so the explanation is excellent.

I'm surprised that there would be one less stop of DR for equivalent photos with the FF but it makes sense after your explanation.

Excellent!

Would similar apply to other IQ factors like colour depth ?

Indeed:

http://www.dxomark.com/index.php/About/In-depth-measurements/Measurements/Color-sensitivity

Color sensitivity is the number of reliably distinguishable colors up to noise. Roughly speaking, two colors are considered as distinguishable if their difference is larger than the noise. In this respect, color sensitivity is the generalization of color to the notion of tonal range.

I suppose that within a generation or two M43 sensors will have similar efficiency to the D800 sensor...

They already do.

...which I've read is getting close to the theoretical limit of sensor efficiency and (barring new technological breakthroughs) the amount of DR available will hit a ceiling.

It will be possible to get endless DR if pixels can reset during an exposure and the bit depth of the image file is larger (say 24 bits).  The problem is representing that DR in a meaningful matter in the output medium (e.g. monitor or print).

So, if you want to maximise DOF and DR, there may be an advantage in choosing a smaller sensor when that occurs (assuming the number of pixels on FF is scaled up proportionately) ?

No, not really.  The Canon 6D, for example is a match for the EM5 for equivalent photos.

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Olymore
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Re: An answer:
In reply to Great Bustard, Apr 28, 2013

Okay, from your last response to my question about maximising DOF and DR I either haven't understood correctly or...

what you mean is that for the FF camera you can get the same DOF and potentially an additional stop of DR by using a slower shutter speed (assuming that's a viable option) .

Your comment earlier where you said "for Equivalent photos, the FF sensor would collect the same amount of light, but the read noise would still be twice as much, so the ratio of the saturation limit to the noise floor would be have as much, and thus one stop less DR"

So if an equivalent photo (presumably using 2 lower F-stops to achieve the same DOF and receiving the same light as an M43 sensor) results in 1 stop less DR at the same shutter speed for sensors of the same efficiency /pixel density  how can a FF frame camera then have more DR when you want to maximise DOF in a landscape photograph unless you lower the shutter speed by 2 stops to increase the total light to 2 stops more than the M43 sensor ?

I'll browse your equivalence  tomorrow for an answer as it's late here

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Great Bustard
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Re: An answer:
In reply to Olymore, Apr 28, 2013

Olymore wrote:

Okay, from your last response to my question about maximising DOF and DR I either haven't understood correctly or...

what you mean is that for the FF camera you can get the same DOF and potentially an additional stop of DR by using a slower shutter speed (assuming that's a viable option) .

Correct.

Your comment earlier where you said "for Equivalent photos, the FF sensor would collect the same amount of light, but the read noise would still be twice as much, so the ratio of the saturation limit to the noise floor would be have as much, and thus one stop less DR"

Correct, based on a FF sensor being made of the same pixels as the mFT sensor.

So if an equivalent photo (presumably using 2 lower F-stops to achieve the same DOF and receiving the same light as an M43 sensor) results in 1 stop less DR at the same shutter speed for sensors of the same efficiency /pixel density...

A FF sensor made of the same pixels as an mFT sensor would not be the same efficiency (they would have the same QE, but not the same read noise / µphoto -- it would be twice as high, which would not be an issue except in dark shadows, keeping in mind that the higher the ISO, the more of the photo that is actually shadow, just with brightening applied by the higher ISO setting -- see gollywop's excellent article).

...how can a FF frame camera then have more DR when you want to maximise DOF in a landscape photograph unless you lower the shutter speed by 2 stops to increase the total light to 2 stops more than the M43 sensor ?

If the sensor is more efficient.  The Canon 6D sensor is slightly less efficient than the EM5 sensor at low ISOs, and equally efficient at higher ISOs.  The D800 sensor is more efficient at low ISOs, and slightly less efficient at high ISOs.

I'll browse your equivalence  tomorrow for an answer as it's late here

Many criticize Equivalence saying that things don't work this way in the real world.  They ignore the conditions of noise / DR equivalence, which requires equally efficient sensors.  The further apart are in efficiency (keeping in mind that the sensor efficiency depends on the ISO setting for many sensors due to differences in read noise), the less exact noise / DR equivalence will be.

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John King
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to DigiMatt, Apr 29, 2013

DigiMatt wrote:

Ricardo Maia wrote:

DigiMatt wrote:

walkaround wrote:

"Total light on the sensor" is a meaningless concept.

The only thing you have demonstrated is your ignorance.

Got to love these spitting posts without any explanation whatsoever...

What more do you want? Equivalence has been explained about 500 times already in the DPR forums. Do you need it repeated 500 more times?

Just read and understand this. I think it will help.

It doesn't really.

It merely makes a very simple explanation of the differences between different formats (that has been well understood since at least 50 years before I was born) into a tortuous, convoluted, complex mess ...

The true purpose of "equivalence theory" is explained here:
http://www.dpreview.com/forums/post/51372419

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pavinder
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"Equivalence" is not "Equivalence" - try a new terminology.
In reply to John King, Apr 29, 2013

Seems to me these endless arguments mainly come down to what people interpret "equivalent" to mean.

There are quantitative interpretations (amount of light hitting sensors etc.) and qualitative interpretations (framing, exposure, DOF etc).

There's absolutely no argument that a larger sensor will generally capture a cleaner, less noisy image.  As an analogy 8x10 negatives contain more information than 110 cartridge film negatives, and digital sensor sizes are simply an electronic version of this.

So perhaps we just need to introduce extra terminology to stop these petty and ultimately irrelevant arguments.

As photographers we simply want to make an image that looks a certain way.
What that means, I would have thought, is pretty obvious:
1. what's in the frame, 2. how light or dark the various parts look, 3. DOF, 4. perspective.

Anything else, such as noise levels, are technical issues, they're not part of the first-level aesthetic qualities of the image as listed above.

Of course to some photographers, only the items 1-4 are relevant, and the technical considerations are considered "extra stuff" which rarely becomes important (unless, for example in extremely low light, they become extremely problematic). As long as their image is "clean enough" many people are happy.  For example if people are printing small, or only shooting for the web.

In this case "equivalent" simply means "looks the same" in those qualities mentioned.  If you took two photos, one with a MFT and the other with a FF, stuck them on the web and they "look the same" then they're "equivalent".

We don't care what f-stop it was, what focal length was used, etc.  And we absolutely don't give a 5h1t at all whether the total amount of light on the sensor was more, or less, or more per unit area or whatever!!

It looks the same = it's equivalent.

So what I'm suggesting is simply that these different interpretations be given different names and then there should be be no more need for bickering.  Of course people will then find something else to bicker about, but that's not our concern here.

I suggest "quantitatively equivalent" and "qualitatively equivalent", or perhaps "aesthetically equivalent".  Yes, I know these are also ambiguous terms, but at least it's providing some basis for mutual agreement.

And most of the threads on this topic would be reduced to a handful of posts or until someone points out "yes, they're aesthetically equivalent but not quantitatively equivalent " or vice versa.

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Great Bustard
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to John King, Apr 29, 2013

John King wrote:

DigiMatt wrote:

Ricardo Maia wrote:

DigiMatt wrote:

walkaround wrote:

"Total light on the sensor" is a meaningless concept.

The only thing you have demonstrated is your ignorance.

Got to love these spitting posts without any explanation whatsoever...

What more do you want? Equivalence has been explained about 500 times already in the DPR forums. Do you need it repeated 500 more times?

Just read and understand this. I think it will help.

It doesn't really.

It merely makes a very simple explanation of the differences between different formats (that has been well understood since at least 50 years before I was born) into a tortuous, convoluted, complex mess ...

The true purpose of "equivalence theory" is explained here:
http://www.dpreview.com/forums/post/51372419

I love that you link someone as clueless as yourself! 

Anyway, glad you came to troll, John.  First of all, no, you didn't understand (and still don't):

http://www.dpreview.com/forums/post/36441248

Your whole argument about "total light" is wrong. If you have some sort of "evidence" that supports your view on this, I would suggest that it is purely coincidence.

Secondly, well, there is no secondly, actually.  Wait, maybe there is -- from the same link:

So please find another whipping boy. I am too old, too sick and too tired to argue the toss with you about these things that properly belong in the Open Talk forum, not here.

Huh.  Apparently you got younger and less sick, eh?  'Cause you just ran over to jump into this thread looking for "entertainment", didn't you?

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JosephScha
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Re: What you have demonstrated is not what they mean by equivalence
In reply to tko, Apr 29, 2013

Your opinion does not match what this page:

http://www.josephjamesphotography.com/equivalence/index.htm

which says that shutter speed *is* included, that's how you make sure you get the same amount of light on both sensors.

I didn't invent this stuff, I am not in the "in" crowd the developed these concepts. But I did read the entire page I just gave you a link to and I printed out some earlier posts that tried to explain it here on dpreview. I referred to them when I wrote the previous post.  You are welcome to disagree, but it's not because what I typed is "wrong".  What I typed matches the reference given above and as much as I expressed I am sure I agree with it.  That doesn't mean it's particularly useful day to day, but it does make sense.

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Great Bustard
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to pavinder, Apr 29, 2013

pavinder wrote:

Seems to me these endless arguments mainly come down to what people interpret "equivalent" to mean.

There are quantitative interpretations (amount of light hitting sensors etc.) and qualitative interpretations (framing, exposure, DOF etc).

There's absolutely no argument that a larger sensor will generally capture a cleaner, less noisy image.  As an analogy 8x10 negatives contain more information than 110 cartridge film negatives, and digital sensor sizes are simply an electronic version of this.

So perhaps we just need to introduce extra terminology to stop these petty and ultimately irrelevant arguments.

As photographers we simply want to make an image that looks a certain way.
What that means, I would have thought, is pretty obvious:
1. what's in the frame, 2. how light or dark the various parts look, 3. DOF, 4. perspective.

Anything else, such as noise levels, are technical issues, they're not part of the first-level aesthetic qualities of the image as listed above.

Of course to some photographers, only the items 1-4 are relevant, and the technical considerations are considered "extra stuff" which rarely becomes important (unless, for example in extremely low light, they become extremely problematic). As long as their image is "clean enough" many people are happy.  For example if people are printing small, or only shooting for the web.

In this case "equivalent" simply means "looks the same" in those qualities mentioned.  If you took two photos, one with a MFT and the other with a FF, stuck them on the web and they "look the same" then they're "equivalent".

We don't care what f-stop it was, what focal length was used, etc.  And we absolutely don't give a 5h1t at all whether the total amount of light on the sensor was more, or less, or more per unit area or whatever!!

It looks the same = it's equivalent.

So what I'm suggesting is simply that these different interpretations be given different names and then there should be be no more need for bickering.  Of course people will then find something else to bicker about, but that's not our concern here.

I suggest "quantitatively equivalent" and "qualitatively equivalent", or perhaps "aesthetically equivalent".  Yes, I know these are also ambiguous terms, but at least it's providing some basis for mutual agreement.

And most of the threads on this topic would be reduced to a handful of posts or until someone points out "yes, they're aesthetically equivalent but not quantitatively equivalent " or vice versa.

I asked earlier today:

http://www.dpreview.com/forums/post/51372996

In terms of the visual properties of the final photo, what parameters do you think are "more equivalent" than the parameters I have used [photos with the same perspective, framing, DOF, shutter speed, and display size]?

From where I sit, I find it ironic that so many would be happy to define "Equivalent" as photos with the same AOV and exposure, despite the fact that they would have rather different visual properties.

What do you think?

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pavinder
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Re: What you have demonstrated is not what they mean by equivalence
In reply to JosephScha, Apr 29, 2013

And this link:
http://www.josephjamesphotography.com/equivalence/index.htm
conflates incompatible terms and properties.

First he chooses "5 equal parameters....visual properties of the final photo, .... independent of the technology".

In the next sentences he hits on noise levels, quantum efficiencies and amount of light on sensors.
And then says that "other visual properties.....may be different"!

How he deems it acceptable to choose a specific 5 visual properties as necessarily the same but allows others to be different gives absolutely no basis for a credible argument.

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pavinder
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to Great Bustard, Apr 29, 2013

Great Bustard wrote:

I asked earlier today:

http://www.dpreview.com/forums/post/51372996

In terms of the visual properties of the final photo, what parameters do you think are "more equivalent" than the parameters I have used [photos with the same perspective, framing, DOF, shutter speed, and display size]?

From where I sit, I find it ironic that so many would be happy to define "Equivalent" as photos with the same AOV and exposure, despite the fact that they would have rather different visual properties.

What do you think?

Of the parameters you used, I'd class perspective, framing and DOF as visual properties.  But shutter speed and display size are technical properties.

Personally I think one needs to choose between

a) visual properties (DOF, framing, bokeh, etc), and

b) technical properties (noise, camera settings, quantum stuff).

Of the parameters you used, I'd class perspective, framing and DOF as visual properties.  But shutter speed and display size are technical properties.

Shutter speed is a technical point.  As are focal length, aperture, ISO and all other camera settings.

One can look at two photos, compare them aesthetically and declare them "visually equivalent" without ever needing to know the shutter speed, aperture or focal length etc., yet alone amount of captured light and so on.

It makes little sense to me to arbitrarily define some visual properties as important and relegate others as not important to the discussion.

But if the discussion is kept to aesthetic vs technical then it becomes much easier.

I also completely agree that it's baffling how people could class photos with the same AOV and exposure as "equivalent" even if they look completely different.

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Great Bustard
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to pavinder, Apr 29, 2013

pavinder wrote:

Great Bustard wrote:

I asked earlier today:

http://www.dpreview.com/forums/post/51372996

In terms of the visual properties of the final photo, what parameters do you think are "more equivalent" than the parameters I have used [photos with the same perspective, framing, DOF, shutter speed, and display size]?

From where I sit, I find it ironic that so many would be happy to define "Equivalent" as photos with the same AOV and exposure, despite the fact that they would have rather different visual properties.

What do you think?

Personally I think one needs to choose between

a) visual properties (DOF, framing, bokeh, etc), and

b) technical properties (noise, camera settings, quantum stuff).

I tend to agree.

Shutter speed is a technical point.

I disagree -- it pertains to motion blur which is a visual property.  For sure, if there is no motion in the scene it is irrelevant, but it's relevant more often than it isn't, methinks.

The same applies to DOF -- if the whole of the scene is within the DOF at any aperture (astrophotography, for example), then DOF is irrelevant.  However, DOF matters more often than it doesn't.

As are focal length, aperture, ISO.

Agreed.

One can look at two photos, compare them aesthetically and declare them "visually equivalent" without ever needing to know the shutter speed or focal length etc.

Again, motion blur.

In any case to me it makes little sense to define some visual properties as important and relegate others as not important to the discussion.

Well, Equivalence doesn't do that.  It talks about visual properties that can be made equal, regardless of the system, and then adds in:

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

If the sensors are equally efficient, this will result in the same total noise.  If the mFT (4/3) lens is twice as sharp as the FF lens, and the 1.6x lens is 1.6x as sharp as the FF lens, the sensors have the same pixel count and AA filter, then all will capture the same detail.

Of course, with more stipulations, you can add in more visual properties.  However, there is a significant difference between "equivalent" and "equal".

But if the discussion is kept to aesthetic vs technical then it becomes much easier.

I kinda think that's exactly what Equivalence, as defined, does.

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pavinder
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to Great Bustard, Apr 29, 2013

Great Bustard wrote:

Shutter speed is a technical point.

I disagree -- it pertains to motion blur which is a visual property.  For sure, if there is no motion in the scene it is irrelevant, but it's relevant more often than it isn't, methinks.

The same applies to DOF -- if the whole of the scene is within the DOF at any aperture (astrophotography, for example), then DOF is irrelevant.  However, DOF matters more often than it doesn't.

I absolutely agree that shutter speed, aperture etc. are critical in affecting the visual properties of an image - that's why we shoose them accordingly.

One can look at two photos, compare them aesthetically and declare them "visually equivalent" without ever needing to know the shutter speed or focal length etc.

Again, motion blur.

Maybe I wasn't clear with my point - that yes, shutter speed affects the visual properties such as motion blur on a moving subject.
Similarly with a static subject, shutter speed is irrelevant.  1/15 at f22 vs. 1/125 at f8 - here the aperture is what makes the difference in terms of DOF.

But I can nevertheless look at and compare two photos taken with different cameras at different settings and say they are "visually equivalent" without needing to know what actual shutter speed/aperture/etc was used in each photo.  I can still say they look the same because they have the same framing, perspective, lightness, DOF, blur etc. without needing to know any of the numbers.

In any case to me it makes little sense to define some visual properties as important and relegate others as not important to the discussion.

Well, Equivalence doesn't do that.  It talks about visual properties that can be made equal, regardless of the system, and then adds in:

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

If the sensors are equally efficient, this will result in the same total noise.  If the mFT (4/3) lens is twice as sharp as the FF lens, and the 1.6x lens is 1.6x as sharp as the FF lens, the sensors have the same pixel count and AA filter, then all will capture the same detail.

Of course, with more stipulations, you can add in more visual properties.  However, there is a significant difference between "equivalent" and "equal".

But if the discussion is kept to aesthetic vs technical then it becomes much easier.

I kinda think that's exactly what Equivalence, as defined, does.

...which is why I suggested using two different terms to avoid people confusing things.

It's like arguing the question "What is Art?".  People have their own interpretations.  Some say only painting and sculpture are Art.  Others include photography and video.  Others allow installations as Art.  And there are also people who do things like cook food in a gallery and call it "Art".

But if we at least agree on "this work is a painting", "this is an installation", "this is a performance" etc. then we are much closer to finding out why we might disagree on the question of "is this thing we're looking at a work of Art?".

Similarly to say "these 2 photos are visually equivalent but not technically equivalent" is far more helpful than to just argue about whether they are "equivalent" under some all-encompassing definition.

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pavinder
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to pavinder, Apr 29, 2013

...And, in terms of how this relates to IQ, I think the conclusion of your linked article sums it up really well.

"Each photographer must balance the operation of a system against its IQ potential not only in concert with the display size of the image, but also with both their skills in photography and post-processing, to decide what system best gets the job done for the type of photography that they do."

However we then will get into discussions of what constitutes "high IQ"!

Can we say "aesthetic IQ" and "technical IQ"?   (・_・)

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Great Bustard
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to pavinder, Apr 29, 2013

pavinder wrote:

Great Bustard wrote:

Shutter speed is a technical point.

I disagree -- it pertains to motion blur which is a visual property.  For sure, if there is no motion in the scene it is irrelevant, but it's relevant more often than it isn't, methinks.

The same applies to DOF -- if the whole of the scene is within the DOF at any aperture (astrophotography, for example), then DOF is irrelevant.  However, DOF matters more often than it doesn't.

I absolutely agree that shutter speed, aperture etc. are critical in affecting the visual properties of an image - that's why we shoose them accordingly.

One can look at two photos, compare them aesthetically and declare them "visually equivalent" without ever needing to know the shutter speed or focal length etc.

Again, motion blur.

Maybe I wasn't clear with my point - that yes, shutter speed affects the visual properties such as motion blur on a moving subject.
Similarly with a static subject, shutter speed is irrelevant.  1/15 at f22 vs. 1/125 at f8 - here the aperture is what makes the difference in terms of DOF.

But I can nevertheless look at and compare two photos taken with different cameras at different settings and say they are "visually equivalent" without needing to know what actual shutter speed/aperture/etc was used in each photo.  I can still say they look the same because they have the same framing, perspective, lightness, DOF, blur etc. without needing to know any of the numbers.

What I'm saying, however, is that if there is "enough" motion in the scene, and the shutter speeds are not the same for both systems, there will be a noticeable difference between the photos.  This is why shutter speed is one of the five parameters of Equivalence as I've defined it.

No, not all scenes have "enough" motion where shutter speed matters, just as, no, not all scenes have "enough" DOF where aperture matters.  But, if DOF is to be considered a visual element that should be equal for Equivalent photos, then so should shutter speed.

In any case to me it makes little sense to define some visual properties as important and relegate others as not important to the discussion.

Well, Equivalence doesn't do that.  It talks about visual properties that can be made equal, regardless of the system, and then adds in:

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

If the sensors are equally efficient, this will result in the same total noise.  If the mFT (4/3) lens is twice as sharp as the FF lens, and the 1.6x lens is 1.6x as sharp as the FF lens, the sensors have the same pixel count and AA filter, then all will capture the same detail.

Of course, with more stipulations, you can add in more visual properties.  However, there is a significant difference between "equivalent" and "equal".

But if the discussion is kept to aesthetic vs technical then it becomes much easier.

I kinda think that's exactly what Equivalence, as defined, does.

...which is why I suggested using two different terms to avoid people confusing things.

It's like arguing the question "What is Art?".  People have their own interpretations.  Some say only painting and sculpture are Art.  Others include photography and video.  Others allow installations as Art.  And there are also people who do things like cook food in a gallery and call it "Art".

But if we at least agree on "this work is a painting", "this is an installation", "this is a performance" etc. then we are much closer to finding out why we might disagree on the question of "is this thing we're looking at a work of Art?".

Similarly to say "these 2 photos are visually equivalent but not technically equivalent" is far more helpful than to just argue about whether they are "equivalent" under some all-encompassing definition.

So, what are your parameters for "visually equivalent" and what are your parameters for "technically equivalent"?  I mean, next thing we know we're going to be talking all sorts of "equivalences" for size, weight, price, AF speed/accuracy, build, etc., etc., etc.

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