[wildman]

whereas I can appreciate "perfection" as an admirable pursuit, it has to be conceded that such perfection sometimes yields limited, if any, practical benefits.

Blasphemy!

[Class A]

But, if I take a shot at Fn ISO xxx with APS-C, and you shoot your FF with same aperture and ISO, and if I get a clean shot, then all this extra light that the FF manages to collect has no practical significance.

You seem to be saying "If APS-C is good enough to give me a good shot then why do I need FF?". This position can of course not be argued. If APS-C is good enough to give you a good shot then of course you don't need anything else.

The same holds for a Q. For many applications and situations the Q and its tiny lenses can give you a "clean shot" so why is there any need for APS-C, FF, or even MF?

[bxf]

You seem to be saying "If APS-C is good enough to give me a good shot then why do I need FF?". This position can of course not be argued. If APS-C is good enough to give you a good shot then of course you don't need anything else.

The same holds for a Q. For many applications and situations the Q and its tiny lenses can give you a "clean shot" so why is there any need for APS-C, FF, or even MF?

I suppose yes, almost, but not quite

I think I'm saying that even if something can be measured, but not seen in realistic viewing conditions, then...

[wildman]

I suppose yes, almost, but not quite

I think I'm saying that even if something can be measured, but not seen in realistic viewing conditions, then...

Any "difference" that makes no real world practical difference is not a difference?

[jsherman999]

I suppose yes, almost, but not quite

I think I'm saying that even if something can be measured, but not seen in realistic viewing conditions, then...

You're correct. If the differences are all academic, there would be no need to bother with stuff like a step up in sensor size.

Thing is, you have to stay within a pretty limited set of shooting parameters your entire life to keep things purely academic. As soon as you start to challenge your equipment, you move out of 'academic differences' and into differences you can see and appreciate.

[bxf]

Any "difference" that makes no real world practical difference is not a difference?

If a tree falls in a forest...

[bxf]

You're correct. If the differences are all academic, there would be no need to bother with stuff like a step up in sensor size.

Thing is, you have to stay within a pretty limited set of shooting parameters your entire life to keep things purely academic. As soon as you start to challenge your equipment, you move out of 'academic differences' and into differences you can see and appreciate.

I understand that different people have different needs, expectations, and criteria by which they evaluate their achievements, especially when one is an artist with some sort of a vision. Not being one myself, all I can do is talk

[ElJamoquio]

I don't really belong in this forum, as I have no great pangs for FF (at least until it can be miniaturized). But, I suspect this is as good a place as any to ask my question.

"Every time" someone on one of the other forums mentions FF vs APS-C lens comparison, somebody will come up with something like "you need an f1.1 lens to produce the same image with APS-C that you'd get with an f1.8 with a FF". So, here is the question:

You are in a situation where you want to take a photo, and you've determined that with your FF gear, you will use a 50mm lens at f1.8, ISO 100. Due to the nature of the subject, DOF is not an issue.

What lens and setting do I need in order to obtain the "same" (in practical terms) image with my APS-C camera. Do I need your theoretical f1.1 lens, or will a 31mm/35mm f1.8 do? If the latter, does it not mean that this constant obsession with equivalence is exaggerated, in the sense that it is not always applicable?

Others have correctly mentioned that the 33mm f/1.1 will produce the same image. The APS-C photograph would need to be at ISO 50 on APS-C to make it more 'equivalent'.

Even if DOF didn't matter, if you have both pics at F/1.8 then the APS-C image would have poorer color. The APS-C image will always have lower sharpness of course, but that's usually less important.

[bxf]

Others have correctly mentioned that the 33mm f/1.1 will produce the same image. The APS-C photograph would need to be at ISO 50 on APS-C to make it more 'equivalent'.

Even if DOF didn't matter, if you have both pics at F/1.8 then the APS-C image would have poorer color. The APS-C image will always have lower sharpness of course, but that's usually less important.

Off hand, I don't recall colour being mentioned as a factor in FF/APS-C discussions. But even if what you say is valid, do we not manipulate colour in PP, to the point where small differences in the initial rendering could be said to be insignificant? Are you implying that this supposedly superior colour from FF means that APS-C is not good enough for true professional results?

[ElJamoquio]

what you say is valid

Thanks!

, do we not manipulate colour in PP, to the point where small differences in the initial rendering could be said to be insignificant?

You can manipulate noise in PP, too. It helps but a ISO 6400 image on APS-C is either going to be noisy or smeared.

As sensors improve and PP algorithms improve that will be less of an issue, of course. On the other hand we're not orders of magnitude away from quantum efficiency now. On the third hand we could go Foveon-like and get a 3x improvement, etc.

Are you implying that this supposedly superior colour from FF means that APS-C is not good enough for true professional results?

That's quite a leap from 'FF has better colors', no? So the answer is, no, I'm not implying that at all. But if it's a 'borderline pro' shot (whatever that means?) in APS-C it will be a 'borderline sub-pro' shot in FF...?

[bxf]

In my comment about manipulating colour in PP I meant that since we manipulate colour, then any imperfection in the initial rendering can be said to be not very significant. But now you've got me thinking more: what does better colour mean? I must assume that "better" means more accurate, otherwise we're talking about in-camera manipulation, which is still manipulation, so there would be no difference if the manipulation is done in-camera or in PP.

Thanks!



You can manipulate noise in PP, too. It helps but a ISO 6400 image on APS-C is either going to be noisy or smeared.

As sensors improve and PP algorithms improve that will be less of an issue, of course. On the other hand we're not orders of magnitude away from quantum efficiency now. On the third hand we could go Foveon-like and get a 3x improvement, etc.



That's quite a leap from 'FF has better colors', no? So the answer is, no, I'm not implying that at all. But if it's a 'borderline pro' shot (whatever that means?) in APS-C it will be a 'borderline sub-pro' shot in FF...?

I suppose when all is said and done, what I'm in effect saying is (as Class A suggested) that good enough is good enough, even if there are measurable differences. And no, I'm not trying to impose my standards on anybody else. I am well aware that my own IQ needs are rather modest. I always recall the old arguments in audio circles about (e.g.) differences of 0.01% in amplifier harmonic distortion, that some people claim to be able to hear, and yet double-blind tests repeatedly failed to confirm such claims.

Interestingly, this thread appeared quite timely: https://www.pentaxforums.com/forums/172-pentax-k-3/247057-k-3-compares-well-d800.html

[wildman]

good enough is good enough, even if there are measurable differences

Yep.
My car can cruise all day at 80 mph. A car that could cruise at 120 mph adds nothing useful for my purposes.
It all depends on if you are make an absolute or relative comparison.

[ElJamoquio]

Yep.
My car can cruise all day at 80 mph. A car that could cruise at 120 mph adds nothing useful for my purposes.
It all depends on if you are make an absolute or relative comparison.

What if the instead of installing a more fuel thirsty engine, we instead improve the aerodynamics of your car? Then you can not only go to 120 mph; but also when you are at 80 mph, you use less fuel as well. Would that be useful to you?

[redrockcoulee]

That depends on what you mean by "practical terms".

I don't see an "obsession with equivalence". I see equivalence being used as a tool to compare lenses between different formats.

Equivalence is of course not a doctrine that prescribes that you must take a photo in one format exactly in the same way that you would have taken it on a different format.

You are obviously free to stop down to even f/8 on your 35mm lens in your example. Why would you not, if you want to?

The one thing you cannot claim, however, is that with a 35/1.8 lens on APS-C you can achieve the same as with a 50/1.8 ].

As one who shoots medium and large format film cameras I have never seen any mention of f stop equivalents when comparing format equivalents. There are numberous charts comparing field of view and not all are the same due to aspect ratio differences. Those charts will give you the equvalent focal lenghts using 35mm as the standard for 645,66,67,69,4X5,5X7 and 8X10 but have never seen any f stops associated with them.

Of course most if not all of these charts were created prior to the "need" for razor thin dof. Or of the apparent need to show one format has better than another My 210 on the 5X7 is about the same as my 150 on the 4X5 for example and although they are like almost all LF lenses 5.6.

It seems like it is a very recent phenoneum to use f stop comparisions between formats. My 150 5.6 with a short extension tube on the Hasselblad is as narrow a DOF I would want on a portrait anyways. I personally like both the eyes and the nose to be in focus

[ElJamoquio]

As one who shoots medium and large format film cameras I have never seen any mention of f stop equivalents when comparing format equivalents.

On a lot of those cameras it's easy(er) to see DOF differences in the viewfinder/screen.

With APS-C finders and stock focusing screens it's tough for me to see DOF even with the DOF preview button.

Nowadays if I'm on a FF camera I still have a mini-panic-attack when I see 'F/11' on the screen, then I calm myself by saying 'it's really only like F/8'.