Originally posted by audiobomber Shutter speed, exposure and distance from the subject (perspective) must be the same
What about the field of view?
Quote: Focal length and aperture must be adjusted for crop factor
So different focal length, therefore different rendering characteristics.
Quote: FOV, DOF, DR, perspective, diffraction and noise will all be similar. For me, this is where the meat is, and it is explained by equivalence theory, not by the exposure triangle.
Noise below the threshold of perception doesn't even matter. Including it in your calculation is ridiculous. SO including that in your calculation is misleading. That is the point. For practical photography, no one cares about noise until it's visible. Once again, as you've stated it, equivalence must be tempered by common sense. Who cares if a small sensor camera has more noise than a large sensor camera, if you can't see either?
Or you can just shoot with the camera and see what you get. No need for a theory to figure that out. As far as I'm concerned you can use theoretical constructions like equivalence or you can use empirical knowledge as in developing "common camera sense." Because of the difference in rendering between different focal lengths. The problem of equivalence is it ignores the strengths of the systems used. As I said, 50mm on FF is not the same as 35mm on APS-c regardless of what equivalence said. Those who stubbornly refuse to acknowledge that are missing a lot of rendering wisdom.
Even different 50mm lenses render differently, Planar designs vs. Distagon Designs, heavily corrected vs. less uncorrected, Macro flat plane vs. 77 style (built for the way people take pictures not for the test charts." There is so much more to lenses than straight up focal length. Especially I'm the wide end. The problem I see with equivalence is when people try to use it to ignore everything but focal length when discussing "the same" image. It just isn't everything you need in many situations.
I have actually seen images taken using equivalence where one image or the other is very different than the other. I have no idea why people advocate looking at image creation from such a limited perspective. My 50 macro is not the same as my 50 1.8, yet we have folks creating the notion that you can use random lenses to create the same picture with different lenses on different formats.
Personally, I'm going with "take a few images at different apertures etc, see what you get." Then you actually know how the lens renders, what the DoF is like, how the out of focus areas are rendered. You know what you've got. Not some theoretical nonsense about how they are the same.
I'm wondering, how does equivalence help with the fact that if I take an APS-c image with my 60-250 and the same image with my DA*200 and a Sigma 18-250, which I have done, one image will be better than the others, and there will be noticeable differences. Same format, same focal length. You get different looking images Equivalence can't even predict how you would the same image with different lenses of the focal length on the same format, so how much use can it be comparing different lenses on different formats.
My issue is equivalence it doesn't go far enough. It's too narrow an approach to the image lens selection, ignoring rendering, lens design, and treatment of out of focus areas, sharpness etc. It's a focus on the relatively un-important and ignoring 3/4s of what you should be looking at. Therefore as much a danger to newbies as not understanding equivalence at all.
Equivalence simply doesn't do what it claims to do, because it leaves out so many parameters. It isn't complicated enough to be of much use. And the only lens I bought because of equivalence, the DA 35 2.4, I don't like, at all. It's probably my least favourite lens. Using equivalence instead of actually trying out the lenses will cost you money. And if you can't figure out what lenses you should be trying out without referring to more than the desired focal length and aperture, equivalence really isn't much help.
Or to say it in a sentence, "it's too simplistic."
it gives you a nice ball park figure for math you can do in your head, while ignoring many important elements of lens design. It's half a theory.
I have no idea why this should have to be repeated over and over. What is it here you don't get?
The difference in rendering between different lens designs? The concept of visible noise? What?
With every lens purchase I've made, the part of lens purchases covered by equivalence are the least important, easiest to understand "off the top of your head." Fo the lenses I've had that have moved on, equivalence didn't save me from buying one lens I didn't like, belief in equivalence may have caused or contributed to those purchases.
Last edited by normhead; 11-11-2017 at 09:58 AM.