"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions
Great Bustard Forum Pro • Posts: 41,906
Re: Your examples do not demonstrate 'equivalence'
1

boggis the cat wrote:

Great Bustard wrote:

boggis the cat wrote:

(Note that the ISO on the 5D is raised 'two stops' to counter the relative aperture being lowered two stops -- ISO isn't really measured in 'stops', thus my quote marks to appease the anal types.)

What is ISO "really measured" in, then?

It's a proxy for sensitivity (or was, in film times).  It relates the exposure to the resulting image density for a given film (rated in ISO or an equivalent scale).

Unitless, I guess.

The point being that you need to factor exposure parameters (aperture and shutter speed) and sensitivity (ISO) to determine a "correctly exposed" photograph.  Use too high an ISO and it will be over-saturated; too low and it will be too dark (and possibly have excessive apparent noise).

Now, since you can start from a correctly exposed photograph of, for example, f/2 1/125" at ISO 100 then change the aperture to f/2.8 (-1 stop) and compensate by either changing the shutter speed to 1/64" or the ISO to 200 it can be useful to consider ISO changes in terms of a 'stop', even though that isn't technically accurate.

Indeed, I tend to consider 'exposure' to mean both exposure proper and ISO, even though that is completely incorrect from a technical point of view -- ISO is not an exposure parameter at all.  This is when I am thinking in terms of a correctly exposed photograph -- so, really, 'exposure' would be my short-form thinking for 'how I want this photograph to look' (generally, balanced or 'correctly exposed').

So if I change the f-ratio or shutter speed by one stop, how do I desribe what I do with the ISO to keep the same exposure without using the term "stop"?

What you should get, in theory, is two 'identical'(ish) shots with the same characteristics -- framing (actually no, due to 3:2 v 4:3, but you should get the same angular coverage across the diagonal), DOF, and also apparent brightness and noise.

You will most likely find that this is not quite the case, due to the 5D being an older design and having a comparatively worse sensor.

However, if you ignore the fact that this doesn't really work in reality, it is a reasonably solid idea.

In reality, it's pretty freakin' close for sensors of the same generation.

Well, you admit that your 'equivalent photographs' concept ignores many image quality parameters.

The 5D and GX1 are not very close so I would expect the results to be skewed against the 5D.

Well, a photo at f/2.8 with the GX1 is going to look more like a photo at f/5.6 with the 5D than a photo at f/2.8, so...

Now, you have to bear in mind that unless noise is an important issue then this is something of an irrelevance (IMO).

There's still DOF.  So I guess you're saying that if noise and DOF (which necessarily means the corners will be rendered significantly different for the vast majority of scenes) don't matter, then, sure.  May as well just use a compact then, right?

DOF is a fairly obvious difference.

Except, you claim that 50mm f/2 on 4/3 is "equivalent to" 100mm f/2 on FF, so this "fairly obvious difference" doesn't seem to matter to you.

Also, I am still wanting to pick up a Panasonic FZ200 to -- shockingly enough -- take photographs with.  It must amaze Panasonic that there are still people stupid enough to want a different set of compromises in some cases and not all want to use "full frame" (aka 135 format) for every purpose.

Funny you say that, 'cause I've recommended the FZ200 to several people, along with the RX100, GX1, etc.

Have you considered writing a spy novel?  You could improve it by making the spy use a 135 system instead of one of those entirely useless tiny spy-camera things to copy the secret documents.

I've also said, countless times, that the vast majority are better suited with systems smaller than FF.  I just love how you, and people like you, constantly, and intentionally, misrepresent me.

Oh, and also bear in mind that my caveats above with respect to 'equivalence' can also be ignored if you use the phrase "all else being equal".  This is what Joe (Great Bustard) prefers to use, and is perfectly fine provided you realise that this is not likely to be the case in reality.

All else is never equal.  But "all else" can often be accounted for.  It's like gravity -- for the most part, we only need to worry about the earth.  But if we want to explain the tides, we have to include the moon.  If we want to explain spring tides, we need to include the sun.  Etc., etc., etc.

Sure, but you can't explain tidal behaviour at a given location purely with reference to the tidal pull of the Moon and Sun (and any other orbiting bodies you may care to include if you like meaningless precision).

This is not to say that the general theory is useless, of course.  Someone could have saved Bill O'Reilly some embarrassment if they'd bothered to explain the general gist of it to him when he was a child, for example.

Fact of the matter is that f/2.8 on mFT (4/3) produces photos much more similar to f/5.6 on FF than f/2.8 on FF.

Great Bustard Forum Pro • Posts: 41,906
Re: An answer:
1

Olymore wrote:

Then, when the pixel density is the same, (so number of MP smaller) and the  sensors have the same QE, the smaller sensored camera would have a DR advantage but a resolution disadvantage assuming the same total light.

No.  Again, it's not the pixel count that matters, but the QE and read noise / µphoto.  The evidence so far shows that pixel size has no effect on QE, but read noise is all over the place with different sensor designs.

Basically I'm hoping that some point in the future when sensors have reached a ceiling for QE  I can carry a 2/3 inch or 1 inch sensored camera up a mountain and get the same DR as a much larger sensor for photos that predominantly require large DOF.

This will be done when pixels can refresh during the exposure and one can effectively have no ISO limit at the bottom end (bit depth of the image file permitting).

However, keep in mind that two photos with the same DR can have quite a different look, since DR does not include photon noise in the measure.

Current resolution and noise is sufficient for me.

Current resolution of what?  Compacts with 2/3 inch sensors?  Same question for noise.

I'll read Gollywop's explanation when I get home tonight.

Thanks for the help

Here's something to think about:  the D800 has more than 2 stops more DR than the Canon 5D3.  What does that mean in terms of IQ?  Try this thread for an answer:

http://www.dpreview.com/forums/post/51364990

Great Bustard Forum Pro • Posts: 41,906
If I might interject....
3

walkaround wrote:

Can you please understand that the point of my original post was merely to show that f/2 is f/2 regardless of the format. To prove that I used identical ISO and shutter speed. Is that so difficult to get? Stop trying to make it about noise, image quality, dof. The EXPOSURES are the same in my post. The light areas are equal lightness and the dark areas are equal darkness. I shoot at base ISO, I don't give a sh*t about sensor noise. I never said "the noise" is the same, or the image quality. And I explicitly stated that the dof is different.

Everyone already knew that f/2 resulted in the same exposure regardless of format and regardless of focal length (for a given scene luminance and shutter speed).  There was nothing to prove.

The point of Equivalence, since you still don't seem to know, is that the same exposure on different formats produces different results, ergo, photos from different formats with the same exposure are *not* equivalent.

And since you "don't give a sh*t about sensor noise", then what is the difference in "exposure" between f/2.8 ISO 100, f/4 ISO 200, f/5.6 ISO 400, etc.?

OP walkaround Senior Member • Posts: 2,551
Re: You are crushing my patience.

ljfinger wrote:

Why do you suppose MF cameras do better in low light than 35mm cameras, or 35mm cameras do better in low light than 110 cameras even when using the same type of film?

Medium Format film cameras "do better" in low light? This is news to me. I thought they just had higher resolution. Source?

OP walkaround Senior Member • Posts: 2,551
Re: If I might interject....

Great Bustard wrote:

Everyone already knew that f/2 resulted in the same exposure regardless of format and regardless of focal length

"Everyone"? I wish that were true, but there are too many posts on dpreview that prove you wrong, including that Sigma reveiw. "Everyone" did not know that, mostly due to confusion sewn by your singular definition of "Equivalence". That's why I posted what I did, even knowing that it would provide you with "entertainment".

The point of Equivalence, since you still don't seem to know, is that the same exposure on different formats produces different results, ergo, photos from different formats with the same exposure are *not* equivalent.

In your narrow definition of the term. Why is your definition more valid than mine?

Great Bustard Forum Pro • Posts: 41,906
Defining "Equivalent"
1

Amin Sabet wrote:

I recently took all my cameras and shot some photos of the same subject from the same distance with them.

These were my settings:

Leica M9 and 35mm lens at f/8, 1/60s, ISO 6400 (2500 pushed 1.3 stops in Lightroom)

Sony NEX-5N and 24mm lens at f/3.2, 1/60s, ISO 1000

Fuji X-E1 and 24mm lens at f/5, 1/60s, ISO 2500

Olympus E-PM2 and 17mm lens at f/4, 1/60s, ISO 1600

I resized all of those to the same diagonal pixel dimension and showed them to a bunch of family and friends, asking the simple question "Which of these images look equivalent to you?"  When pressed to explain what I meant by equivalent, I offered the guidance "Similar in visual properties".

Good test.

According to Joe's proposed definition of "equivalent images", the Leica, Fuji, and Olympus images were equivalent, and the Sony not equivalent.  Indeed, I could tell that the Sony image had less DOF than the others.  Yet everyone picked the Sony, Fuji, and Oly shots as equivalent, noting that the obvious difference in visual properties was how noisy the Leica image looked.  The second most common observation had to do with slight differences in color rendition.  No one commented on the DOF differences, including my wife who often complains about a photo being blurry when I use a narrow DOF.

So, is it fair to say that your conclusion is that noise and color are more significant than DOF?  I would certainly agree, depending on the differences between noise, color, and DOF.  Same goes with other elements of IQ, such as detail, bokeh, moire, etc.,

To some people, a 35/1.4 on a Leica M9 doesn't produce an image equivalent to one made with a 35/1.4 on a D800.  To this guy, a Canon 35/1.4 on a 5D III doesn't produce an image equivalent to one made with a Sigma 35/1.4 on a D800.

Of course, "equivalent" does not mean "equal".

Arguing about what is equivalent is like arguing about what is compact.  There is no accepted definition other than the common use as pertains to focal length equivalents.  There is a proposed definition of "equivalent image" but not an accepted one.

Equivalent photos, as I define them, are photos with the same perspective, framing, DOF, shutter speed, and display size.  They are independent of the technology used to capture the photo.  Other elements of IQ, such as detail, noise, dynamic range, color, etc., all may matter more than any of the five parameters of Equivalence, depending on the scene in question.

What I find interesting is that no one would object to Equivalence being defined as "same AOV and exposure".  I dare say, you'd never have bothered with the test if Equivalence had been defined in such a manner.

Lee Jay Forum Pro • Posts: 53,181
Re: You are crushing my patience.
2

walkaround wrote:

ljfinger wrote:

Why do you suppose MF cameras do better in low light than 35mm cameras, or 35mm cameras do better in low light than 110 cameras even when using the same type of film?

Medium Format film cameras "do better" in low light? This is news to me. I thought they just had higher resolution. Source?

Source?  Are you kidding?  You ever shot with different formats on film?  35mm was bad, but 110 was much worse!  2 1/4 x 2 1/4 (and other medium formats) was a good bit better.  Much less visible grain at the same ISO.

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JosephScha Veteran Member • Posts: 5,376
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
1

Re: "many people would seem to doubt this simple fact"

Yes, and that is the worst part about this ongoing discussion of "equivalence". It is not intuitive that what they mean by its definition CAN NOT include equivalent exposure.  It confuses many people who think equivalence must include equivalent exposure.  They assume it does, and somehow think that f/4 on full frame needs f/2.8 on m43 for exposure reasons.  That is absolutely not true, those people have been misled.

By using the same aperture diameter (instead of f stop) and the same shutter speed, the "equivalence" crowd are achieving the same total light reaching the sensor, which means that the larger sensor has less light per unit area, that is, less exposure. So to make up for that, the system with the larger sensor has to raise ISO ... So IF the sensors are equally efficient then the noise will be the same.

Since the two systems use the same aperture diameter they will have the same DOF.

Since they have the same shutter speed they should have the same motion blur.

And of course the framing and display size should be the same.  This clearly means that they don't compare 100% view, because that would not be the same display size for two sensors with different number of megapixels.

So I think they do have a point about comparing pictures which SHOULD be indistinguishable, so if they are distinguishable you can say something about the two cameras.  The pictures you posted (which have same exposure, that is same f/stop and same ISO) are easily distinguishable, the one with much less depth of field is the SLR.  Of course what JJ (GreatBustard)'s definition of equivalence is tries to take away that possible advantage of an SLR by asking how it does with the same aperture diameter, not the same f stop.  And that's exactly what is non-intuitive ... "but, you COULD use f/2 or even less on a DSLR and stay at base ISO"  ... yup, you could.  Equivalent exposure.  A very comfortable concept for me.

The stretch is to try to grant that the other definition of equivalence might have a purpose, and does not need to be shot down or decried. No one is forced to use it to compare systems, they are just proposing that would be a good way.  And it doesn't take into account features like autofocus speed, movie modes, anything like that, which people will consider.  It's just one proposed way to compare.

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js

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Great Bustard Forum Pro • Posts: 41,906
Re: If I might interject....
2

walkaround wrote:

Great Bustard wrote:

Everyone already knew that f/2 resulted in the same exposure regardless of format and regardless of focal length

"Everyone"? I wish that were true, but there are too many posts on dpreview that prove you wrong, including that Sigma reveiw. "Everyone" did not know that, mostly due to confusion sewn by your singular definition of "Equivalence". That's why I posted what I did, even knowing that it would provide you with "entertainment".

Please link and quote a post where someone did not understand that f/2 resulted in the same exposure regardless of format and regardless of focal length for a given scene luminance and shutter speed.

You mention the Sigma review.  Please link and quote the portion.

The point of Equivalence, since you still don't seem to know, is that the same exposure on different formats produces different results, ergo, photos from different formats with the same exposure are *not* equivalent.

In your narrow definition of the term. Why is your definition more valid than mine?

What's your definition?

Great Bustard Forum Pro • Posts: 41,906
How did I say it?

pidera wrote:

Yes I had to read that paragrph twice and decided it was best to ignore it

Note (as I am still typing) : in the lost post I wrote something like this : Equivalency is at it's best when used in it's most simple form, ignoring things like read noise, bellows factors, t-stops and stuff like that. If all all connexions in the brain are right, one should experience some kind of insight, not yet mudded by other details. By trying to 'prove' too much hower (like the superiority of one system over another), one often ends up 'proving' nothing at all.

I think it was something like this:

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

  • 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.
OP walkaround Senior Member • Posts: 2,551
Re: You are crushing my patience.

ljfinger wrote:
35mm was bad, but 110 was much worse!  2 1/4 x 2 1/4 (and other medium formats) was a good bit better.  Much less visible grain at the same ISO

But isn't this because of the relative enlargement sizes? The larger negative has to be blown up less for the typical print sizes. Film doesn't have one grain size. The larger grains in an ISO 100 film are actually ISO 400 or more. In the shadows on a fast exposure these larger grains are the only ones exposed, and so when you enlarge the 35mm negative 20 times you see it.

Yohan Pamudji Senior Member • Posts: 2,874
Re: Not to crush your spirit....
1

ljfinger wrote:

walkaround wrote:

ljfinger wrote:

But I'm going to crush your spirit.

Equivalent images all have identical:

- ISO

- Shutter Speed

- Aperture

- Framing

Anyone who says "equivalence" means something other than the above is an idiot.

As shown in my samples, those don't result in equivalent images.

Anyone who disagrees with my definition of "equivalence" is an idiot.

So, to you, the EXIF data is more important than the images.  To most of us, the images are more important than the settings used to take the images.

I don't think he's willing to listen to any viewpoints that contradict his faulty understanding.  Those of us who understand the basic elements of a photograph (composition, perspective, brightness, depth of field, blur/lack thereof) are in agreement, but strangely enough it's not a universally accepted concept that equivalent photos by definition should have the same DOF.  Strange but true.  Your post reduced that strange idea to its understandably absurd conclusion, but the OP still didn't get the point.  Might be time to pack up and let him be.

Lee Jay Forum Pro • Posts: 53,181
Re: You are crushing my patience.
1

walkaround wrote:

ljfinger wrote:
35mm was bad, but 110 was much worse!  2 1/4 x 2 1/4 (and other medium formats) was a good bit better.  Much less visible grain at the same ISO

But isn't this because of the relative enlargement sizes?

The two explanations are the same.  The bigger film is better because of statistics - more light has been captured and since signal-to-noise ratio goes with the square root of the number of photons captured, more photons equals higher SnR.

Put it another way - the equivalent way!

If you double the grain size in each direction, you'll go from (say) ISO 100 film to ISO 400 film.  Now use a piece of film twice as large, enlarge it half as much, and you'll get the same image with each format - equivalent images!  But you'll over-expose that larger film if you don't use equivalent settings, which means 2 stops lower exposure for the larger, more sensitive piece of film.

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Great Bustard Forum Pro • Posts: 41,906
Re: ... comparison continued (crops)

boggis the cat wrote:

pidera wrote:

Canon 5d iso1600

Canon g7 iso80

I see roughly the same amount of noise in the iso1600 image as in the iso80 image. As expected given the cropfactor of roughly 4,75.

The results are quite similar.  The G7 result looks better to me, including less noise, but that could be due to the processing and / or better optical performance (with the 135 lens stopped down to f/22).

The main differences to my eyes is color and noise.  The G7 no doubt has a more efficient sensor than the 5D (the QE of the 5D is a measly 25%), which accounts for the noise differential.  I assume that color can be dealt with in processing.

However, as far as lens performance goes, all systems suffer the same diffraction softening at the same DOF, so it's unlikely that optical performance would be a player at apertures dominated by diffraction softening.

pidera Contributing Member • Posts: 913
Yes that's fine !

I'm not a regular visitor of your site, but you did well Joe with adding this kind of quick explanations. You've clearly moved on since a while. I also found the 'evidence' sector with links. It is quite a scroll (or click) down though. Adding a few images within the tekst would help imho.

Regards, P.

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Yohan Pamudji Senior Member • Posts: 2,874
One last stab
1

walkaround,

I'm going to take one last stab at this in the hope that there's some common ground to be had.

Ignore all the physics mumbo jumbo for now.  None of that "total light" vs. "light per unit of area", etc.  They're important in a way and govern the principles that we live by when making photographs, but it's not necessary to understand all the intricate physics and math to get the concept of equivalence.

The basic idea behind equivalence is simply this question: "What does it take to make the same photograph on 2 different sensor sizes?"  That is the heart of the matter.  What are the basic characteristics of a photograph?  I don't think it's radical to say that these are the basics:

Composition/framing
Perspective
Brightness
Depth of field
Motion blur or lack thereof
Color or lack thereof
Noise

Notice that none of those are actual in-camera settings.  That is, we can set our camera to get certain effects in each category but the direct in-camera settings aren't what we're trying to equalize.  In fact sensor size differences force us to use different in-camera settings to achieve the particular photographic look we're after.

What you are talking about is using the same exposure settings on 2 different formats--aperture, shutter, ISO--which will result in the same brightness but definitely not the same image because DOF is different.  While it is worth knowing that using the same exposure settings on different formats will result in the same brightness, I would hope that's something so basic that it's well-understood.  What equivalence addresses is the fact that the same exposure settings don't actually give you the same photograph if you're comparing 2 photos taken with different sensor sizes.  And isn't DOF a crucial element in a photo?  That's not a radical or narrow definition, is it?

That's really all there is to it.  Once you agree with those statements you can then start unpacking the rest of the argument, i.e.:

  • What aperture do you have to use to get the same DOF on different sensor sizes?
  • When you change the aperture to get the same DOF how do you have to change the ISO to maintain the same brightness?
  • And finally when you change the ISO are you still getting the same amount of noise in the photo and how does the higher/lower ISO affect color fidelity, etc.?

That's the thought progression.  Hope that helps.

Hen3ry
Hen3ry Forum Pro • Posts: 18,218
Question of equivalence; ah, nostalgia!
1

walkaround wrote:

There has been a lot of talk by a few people here about "total light", and how an f/1.4 lens on a m4/3 camera supposedly acts like an f/2.8 in regards to "light on the sensor", etc. No examples have been given in those threads, so I thought I would post some test shots I just did.

Both photos were taken at ISO 160, 1/250, f/2.0
I have not edited the out of camera jpegs in any way. Other than slight differences in the magnification of the two lenses, WB, and the obvious DOF difference, the exposures are equivalent. They are the same. When I print both photos on 4x6, they look the same. "Total light on the sensor" is a meaningless concept. Exposure and density is not.

"Meaningless concept"? -- not theoretically. I grok it.

"Irrelevant" is the word that springs to mind for nearly all photographers nearly all of the time.

An f-stop is an f-stop, a shutter speed is a shutter speed, and an ISO is an ISO (although various manufacturers fudge the latter a little just as in the old days the film manufacturers fudged things a little in respect of sensitivity). So f2 @ 1/200 with a 25mm focal length lens on m43 produces an image of near enough to the same density and general characteristics as f2 @ 1/200 with a 50mm on FF.

The large and medium format users back in the old film days used to waffle on endlessly about quality and whatnot; in the end the (little) 35mm format won out for its smallness, lightness, handiness, and with improvements in film technology, perfectly satisfactory IQ for nearly all amateur and most professional applications.

And here it is all over again with the noose tightening around the "big" format -- now FF (35mm equiv!) and its supporters desperately summoning esoterica to boost their armament as their flailing mirrors fail to repel the smaller format, more technologically advanced visigoths which are swallowing up their outposts one by one.

Just as it did back in the day when the 35mm barbarians were at the IQ gates.

Oh dear! It does bring a tear to the eye. Tear of laughter, that is!

I am one of the "nearly all" and am enjoying both my professional and leisure photography enormously, thanks, with my E-PL3 and such dedicated lenses as the Panny f2.5 14mm (28mm equiv) and the Oly 40-150 zoom (80-300 equiv) at ISO 200 nearly all the time. LOL.

But I really do enjoy seeing the FFers working themselves up into a lather about DoF, total light to the sensor, bokeh, etc. In particular, bokeh. Sure, that is linked to DoF but the biggest contributor to nice bokeh, in my book, is having the light coming through a circular or near circular orifice. Like the Oly f1.8 45mm (90mm equiv, LOL) I use for most portraiture.

Cheers, geoff

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Great Bustard Forum Pro • Posts: 41,906
You say, "An f-stop is an f-stop...
3

Hen3ry wrote:

An f-stop is an f-stop, a shutter speed is a shutter speed, and an ISO is an ISO (although various manufacturers fudge the latter a little just as in the old days the film manufacturers fudged things a little in respect of sensitivity). So f2 @ 1/200 with a 25mm focal length lens on m43 produces an image of near enough to the same density and general characteristics as f2 @ 1/200 with a 50mm on FF.

...a shutter speed is a shutter speed, and and ISO is an ISO."  But apparently you stop short of focal length.  That is, you didn't say "A focal length is a focal length."

I find that omission curious.

That is, just as the effect of 25mm on mFT has the same effect as 50mm on FF, the effect of f/2 on mFT has the same effect as f/4 on FF.  And yet you feel "an f-stop is an f-stop" but apparently don't think that "a focal length is a focal length".

Like I said -- curious.

OP walkaround Senior Member • Posts: 2,551
Re: One last stab

Yohan Pamudji wrote:

What you are talking about is using the same exposure settings on 2 different formats--aperture, shutter, ISO--which will result in the same brightness

Yes. You think this is self apparent, but to others it is not. And dpreview adds to the confusion:

"Sigma's choice of F1.8 as maximum aperture isn't a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What's more, it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that's just over twice as bright onto a sensor that's slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it's a major determinant of image quality."

(my emphasis)

The part that I put in bold above is only true (and only interesting) if your primary concern is image noise. If you are concerned, like most people taking a photograph, with "brightness" ie exposure, then it is not true. To the individual pixel or film grain the lens is an f/1.8 lens.

So you can save your explanations, I am fully aware of what the equivalence gang defines as "equivalence". I find it funny that I'm being called ignorant and insulted for pointing out what several of you have admitted is accepted fact, even "obvious".

Great Bustard Forum Pro • Posts: 41,906
"Adding to the confusion"
1

walkaround wrote:

Yohan Pamudji wrote:

What you are talking about is using the same exposure settings on 2 different formats--aperture, shutter, ISO--which will result in the same brightness

Yes. You think this is self apparent, but to others it is not. And dpreview adds to the confusion:

"Sigma's choice of F1.8 as maximum aperture isn't a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What's more, it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that's just over twice as bright onto a sensor that's slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it's a major determinant of image quality."

(my emphasis)

The part that I put in bold above is only true (and only interesting) if your primary concern is image noise. If you are concerned, like most people taking a photograph, with "brightness" ie exposure, then it is not true. To the individual pixel or film grain the lens is an f/1.8 lens.

If neither noise nor DOF are an issue, then you can shoot whatever f-ratio and shutter speed you desire.  I believe I asked you the following earlier:

http://www.dpreview.com/forums/post/51377964

And since you "don't give a sh*t about sensor noise", then what is the difference in "exposure" between f/2.8 ISO 100, f/4 ISO 200, f/5.6 ISO 400, etc.?

Well?

So you can save your explanations, I am fully aware of what the equivalence gang defines as "equivalence". I find it funny that I'm being called ignorant and insulted for pointing out what several of you have admitted is accepted fact, even "obvious".

Wasn't it you who said:

http://www.dpreview.com/forums/post/51377460

Equivalent images all have identical:

- ISO

- Shutter Speed

- Aperture

- Framing

Anyone who says "equivalence" means something other than the above is an idiot.

Anyone who disagrees with my definition of "equivalence" is an idiot.

Hmm.

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