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09-04-2011, 07:25 AM - 1 Like   #16
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QuoteOriginally posted by Digitalis Quote
It pays to be careful, there have been quite a few misinformed users on the forums that-shall-not-be-named that have said that a full frame sensor by virtue of its greater area receives more light from the lens and smaller APS-C sensors that have a smaller area receive less light.
You are wrong and those other "misinformed users" are correct. The aperture specifies the illuminance, which is the luminous flux that makes it to the sensor per unit area. For a given f-stop this is in fact the same across camera systems (ignoring transmittance loss, which we seem to do in still photography, though it's darned important).

Thus a larger sensor does in fact collect more light -- simply multiply the constant flux by the larger area. This is why, all other factors being equal, larger sensors produce better images (define "better" in terms of signal to noise, dynamic range, whatever).

QuoteOriginally posted by Digitalis Quote
there isn't any cropping going on here - cropping is what a photographer does to a photograph after it is taken. APS-C is is simply a different format, to use the term "cropping" is misleading.
On the contrary, take exactly the same photo with an APS-C camera and a 35mm camera. By "same" I mean perspective, focal length, aperture etc. The result is equivalent to cropping the larger image in the same proportion as the sensor sizes. Using a smaller sensor is like throwing away the extra parts of the image that do not fit into the crop. The term cropping is the simplest way to explain this relationship and is is hence entirely appropriate.

QuoteOriginally posted by Jüri Quote
So to answer the inquiry of original poster, full frame 50mm lens does not replace a 75mm APS-C lens one to one. When both are compared on a Pentax dSLR, the latter will give narrower prespective.
No, perspective is only a matter of where you stand relative to your subject. It has nothing to do with sensors or lenses. I believe you mean "narrower field of view".

QuoteOriginally posted by billtin59 Quote
To me, all this talk of "crop factors" is a waste of time.
Except for those who wish to understand. In this day and age people are swapping lenses between different sensors more than ever. Hence it is important to understand equivalency. I wrote an article on the topic but apparently no-one reads it, or any that preceded them by other authors.

I applaud the OP for trying the experiment themselves.

09-04-2011, 07:58 AM   #17
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QuoteOriginally posted by billtin59 Quote
To me, all this talk of "crop factors" is a waste of time. It's just tech jargon that you don't really need to know since with an SLR, pretty much what you see is what you get. Forget about the crop factor and think more about composition and exposure. Your pics will never improve thinking about crop factors!
Yep. Me too. I've never given it a second thought and only read these threads for some mild entertainment. I get the OPs point, simply stating that he sees the difference of the Same lens on two different formats. For all of the rest of the discussion, it doesn't matter to me. I've always put a lens on a camera (regardless of format) focused, let the camera meter tell me what the exposure needs to be, and taken the photo. If I can't get far enough away, I know I need a wider lens. If I can't get close enough, I need more of a telephoto lens.

09-04-2011, 08:36 AM   #18
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QuoteOriginally posted by JeffJS Quote
Yep. Me too. I've never given it a second thought and only read these threads for some mild entertainment. I get the OPs point, simply stating that he sees the difference of the Same lens on two different formats. For all of the rest of the discussion, it doesn't matter to me.
I sure didn't mean to re-start the crap.factor (German: formatfaktor) wars. And I was careful not to say crap.factor -- but the FL vs FOV+DOF effects between various formats can't be avoided.

No, moving a lens to a different camera doesn't change its focal length. No, it doesn't matter what format a lens is made for, except that smaller-format lenses may vignette on larger-format frames. Yes, for a given lens, a smaller frame essentially crops more of the projected image than does a larger frame.

And yes, rather than compare the rough equivalences of focal lengths on various formats, it's more productive to know what each focal length will DO on any given format. Back before the marketing wonks came up with the term crap.factor, we just learned what FLs were 'normal' for each format, and extrapolated from there. The frame diagonal is 'normal'. Shorter than that is 'wide', longer is 'tele'. It ain't rocket science.

Yet constants hold -- the relationships between exposure, perspective, distance, etc. We balance and exploit these factors; every photograph is a problem to be solved, with infinite solutions. Equivalences are mental crutches, shortcuts to finding those solutions.
09-04-2011, 12:42 PM   #19
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QuoteOriginally posted by rparmar Quote
Originally posted by billtin59 To me, all this talk of "crop factors" is a waste of time.
QuoteOriginally posted by rparmar Quote
Except for those who wish to understand. In this day and age people are swapping lenses between different sensors more than ever. Hence it is important to understand equivalency. I wrote an article on the topic but apparently no-one reads it, or any that preceded them by other authors.
What part of "TO ME" do you not understand professor?

09-04-2011, 12:57 PM   #20
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QuoteOriginally posted by billtin59 Quote
To me, all this talk of "crop factors" is a waste of time. It's just tech jargon that you don't really need to know since with an SLR, pretty much what you see is what you get. Forget about the crop factor and think more about composition and exposure. Your pics will never improve thinking about crop factors!
For me personally crop factor is very important, since I use both Pentax SLR and dSLR. For instance my 19-35mm lens gives an awesome field of view on the SLR, but using it on dSLR makes no sense. I agree that when shooting with a 50mm lens there isn't much difference which camera you use, but it'll start making a lot of difference the wider you go.
09-04-2011, 01:33 PM   #21
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QuoteOriginally posted by Jüri Quote
For me personally crop factor is very important, since I use both Pentax SLR and dSLR. For instance my 19-35mm lens gives an awesome field of view on the SLR, but using it on dSLR makes no sense. I agree that when shooting with a 50mm lens there isn't much difference which camera you use, but it'll start making a lot of difference the wider you go.
Tell me, did you come to that conclusion about the FOV by looking through the viewfinder, or by learning what the crop factor was all about?
09-04-2011, 01:41 PM   #22
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QuoteOriginally posted by billtin59 Quote
What part of "TO ME" do you not understand professor?
Your belligerence in your response betrays your true feelings on this matter. If your opinion was only "for you" then you would not post here on a public forum; you would instead be content with yourself in the comfort of your own domain. But instead you made the decision to promulgate your opinion. Yet you are annoyed when others do likewise.

Second: By declaring this matter "a waste of time" and then yourself commenting on it, you confirm that you are also wasting time, but doubly so since you are conscious of the matter.

Which part of "contradiction" do you not understand?
09-04-2011, 02:13 PM   #23
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QuoteOriginally posted by rparmar Quote
Your belligerence in your response betrays your true feelings on this matter. If your opinion was only "for you" then you would not post here on a public forum; you would instead be content with yourself in the comfort of your own domain. But instead you made the decision to promulgate your opinion. Yet you are annoyed when others do likewise.

Second: By declaring this matter "a waste of time" and then yourself commenting on it, you confirm that you are also wasting time, but doubly so since you are conscious of the matter.

Which part of "contradiction" do you not understand?


The ONLY reason I come to this forum IS to waste time, when I have something better to do, I DO IT!!

Your promulgation is annoying because you use it to try to promote an article YOU wrote which apparently NO ONE wants to read!

Lastly, the OP AGREED with my statement, so PTHTHTHTHT!!!


Last edited by Peter Zack; 09-04-2011 at 02:43 PM. Reason: Rude Comments
09-04-2011, 02:18 PM   #24
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Well, nothing I can say could possibly paint you in a worse light. Thanks for saving me some typing!

P.S. I don't use words just to annoy you, but rather to accurately communicate. You might find it hard to believe, but some of us enjoy helping each other and furthering knowledge.
09-05-2011, 04:57 AM   #25
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QuoteOriginally posted by pop4 Quote
Did you also notice that there wasn't any magnification? The field of view changed, but you got no added magnification by putting the 50 on the K-r.
I don't know about film resolution versus the kx resolution, but I do know that if you take a photo with a D3 and a kx (both 12 megapixel cameras), the kx image will seem magnified versus the D3 photo. The big question is the pixel pitch, which is quite large on most of the Nikon full frame cameras and is small on current APS-C cameras.
09-05-2011, 05:25 AM   #26
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QuoteOriginally posted by rparmar Quote
Thus a larger sensor does in fact collect more light -- simply multiply the constant flux by the larger area. This is why, all other factors being equal, larger sensors produce better images (define "better" in terms of signal to noise, dynamic range, whatever).
I don't think you understood what I was getting at. A 50mm f/1.4 at f/1.4 the 24X36mm sensor has light of exactly the same intensity as the light that falls upon the APS-C sensor with the same lens at the same aperture,the only thing has changes is the area that the light is spread over. Many people believe that the full frame sensor - because of it's larger area is getting more light and therefore the exposure will be different from APS-C which is absolute rubbish - but many "misinformed users" will defend this hair-brained theorey even in the face of solid evidence.
09-05-2011, 05:31 AM   #27
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I'm not a skilled photographer, but I am an experienced computer programmer. What matters today is not the total amount of light hitting the sensor, but the quality of each captured pixel. Too much light is actually worse for that than too little. The rest is down to processing, in the sensor, in the camera, in whatever post processing you use, and even in the priniting or display technology. .

As for the lenses, what you see is what you get. There is no such thing as a 35mm digital camera, just different sensor sizes that produce different sized pictures, just like different film sizes do. That doesn't change anything about the lens. Even on a 35mm camera the lens can see more than the film does. Only a circular format would record everything, and square would be better than 35mm if recording everything we 'see' through the camera was our goal - except that it isn't because we as humans have been shown in most cases to prefer some sort of 'cropping' to a picture that is wider than it is high and that is in effect built into all the cameras under discussion.

We are supposed to compose our picture based on what we see through the viewfinder - isn't that why we prefer SLR's?

Given the popularity of wider TV formats, how long before someone produces a camera with a different ratio sensor so when you show your piccies to the neighbours on your TV they don't look 'cropped'?

PS there is of course the issue of lenses designed for smaller sensors within a given mount vignetting on larger sensors, but that's a manufacturing decision for sake of cost and compactness - its not to do with focal length or absolute sensor size.

Last edited by redbirdpete; 09-05-2011 at 05:35 AM. Reason: point about vignetting
09-05-2011, 05:40 AM   #28
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QuoteOriginally posted by redbirdpete Quote
Too much light is actually worse for that than too little
when you are optimising the DR of each shot and trying to keep the noise level down ETTR* is my method of choice, Underexposing is simply the wrong way of dealing with noisy high ISO values. With certain negative film emulsions** it was always preferable to overexpose by 1/3rd of a stop to prevent the shadows from blocking up.

QuoteOriginally posted by redbirdpete Quote
We are supposed to compose our picture based on what we see through the viewfinder - isn't that why we prefer SLR's?
Funny thing is that with rangefinders you use framelines that indicate the focal length you are using in the viewfinder - you can still see everything that is going on outside those lines - which is actually quite useful.

*Expose To The Right
**Ilford Pan-F 50 was famous for needing a bit of extra over exposure.
09-05-2011, 05:53 AM   #29
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QuoteOriginally posted by Digitalis Quote
when you are optimising the DR of each shot and trying to keep the noise level down ETTR* is my method of choice, Underexposing is simply the wrong way of dealing with noisy high ISO values. With certain negative film emulsions** it was always preferable to overexpose by 1/3rd of a stop to prevent the shadows from blocking up.
OK, but I'm not talking film. With sensors, at the pixel level, overexpose significantly and you get nothing, underexpose and you have something you can probably salvage when you get it in the computer. As a computer programmer I hate to lose information :-)

I mostly take action photos, so there's often only one chance - I underexpose the main feature if the contrast is so high on a test shot before the action happens) that i'm getting burn out on another part of the picture (usually the sky or reflected highlights), you then still have almost all the information stored and you can bring it back up later. I haven't noticed that this produces no information in the shadows, you just have to tweak to bring it out. As I say, I'm not an expert photographer, so that may be the wrong way to do it.

I used to have a neat little Rollei rangefinder I carried about with me, but we use SLR's most of the time cos they are generally better for picture composition? Don't we?
09-05-2011, 06:21 AM   #30
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QuoteOriginally posted by redbirdpete Quote
'm not talking film. With sensors, at the pixel level, overexpose significantly and you get nothing, underexpose and you have something you can probably salvage when you get it in the computer. As a computer programmer I hate to lose information :-)
Film and sensors are essentially the same thing they both record an image - and when you over expose you lose information on both mediums - though film has a distinct contrast curve that digital sensors do not have - they are linear. Did you know that digital camera sensors CCD's and CMOS are actually analogue devices? the interesting thing is that the tiny microscopic grains of silver halide in film are actually digital - because a grain of silver halide has only two states: exposed and un-exposed - Essentially Film is Binary.

the problem with underexposure with digital is that the overall signal to noise ratio is lowered, meaning that the signal(image data) gets swamped by electronic noise of all kinds and of course there is always the hotly debated subject of the amount of Bits in an image 8Bit Vs 12~14 bit ( Only high end medium format digital backs capture images in true 16 Bit)

QuoteOriginally posted by redbirdpete Quote
but we use SLR's most of the time cos they are generally better for picture composition? Don't we?
As far as i'm concerned it doesn't matter if you use a SLR, rangefinder or a View camera - the end result is what matters, I actually find composition on a view camera much easier - because the image is upisde down and reversed laterally so it lets you see the image in a more objective and analytical way.
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