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05-13-2010, 02:01 PM   #31
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QuoteOriginally posted by Class A Quote
With all due respect, Marc, I think that adding a "digital vs film" dimension to the "changes in focal lengths and aperture" + "change in format" dimensions isn't helpful.
Well, I didn't "add" that dimension; it was already made. I was just responding to it, saying that *if* one wants to add that dimension, it's important to try to separate out the effect of the format *size* from the effect of the format *technology*.

QuoteQuote:
Regarding the original "135/2.8 on APS-C == 200/2.8 on APS-C" discussion: It is pretty easy to see that this equivalence doesn't hold in terms of DOF.
Absolutely.

QuoteQuote:
And this is not the result of losing resolution because of the cropping and subsequent enlargement. The real reason is that less total light is used for the cropped out part of the 135/2.8 shot compared to the 200/2.8 shot.
I might argue that these are inseparable.

QuoteQuote:
Let's cherish our old lenses for what they are on APS-C but let's abstain from making invalid comparisons on what they might be equivalent to on an FF camera.
OK, but I still like making *valid* comparisons...

05-13-2010, 02:17 PM   #32
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QuoteOriginally posted by Blue Quote
Neither thread had anything to do with anyone claiming 1600 ISO film had better IQ than 1600 on a digital sensor.
Well, of course not - it's the other way around. That is the the entire point I am making in this thread - that APS-C digital is significantly *better* than film, and that this fact has implications for the utility of a given lens.

QuoteQuote:
Both threads had to do with aperture speeds
OK, but again, two *completely* different points being made. You just don't seem to be understanding what I am writing here, which is unfortunate, as I think it's creating an argument when we don't really disagree in the way you seem to think.

QuoteQuote:
frankly, a half a stop can be significant given that the next largest full stop is 2x the light the previous stop.
It can be if you reduce it to numbers with no actual context. I'm talkng about looking at *actual images*. That is, comparing an image shot at f/1.4 and ISO 800 (say) against one shot at f/1.7 and ISO 1150. I actually rather doubt most people could spot the difference without extreme pixel peeping. Except with respect to DOF, but for the purpose we were discussing, that difference would be *in favor* of the f/1.7 shot.

Anyhow, maybe *for your purposes*, the f/1.4 ISO 800 would be so much preferable to the f/1.7 ISO 1150 shot that the latter would not suffice. But I suspect that for most people, it would be a toss up, and whatever advantage they saw in the former shot would not worth spending 2-3 as much on the lens to get. If you agree, fine, we can agree to disagree on the *magnitude* of the difference as it affects us personally. But so far, the argument has been on the *nature* of the difference, with us just talking two completely different languages. That's the part I consider unfortunate.

QuoteQuote:
Regardless, an f2.8 135mm lens is a f2.8 135mm lens.
Of course, and no one would ever suggest otherwise. The issue is not what the lens *is*, but on what capabilities it has in practice, and those capabilities are in part determined by the format.

QuoteQuote:
When an optics lab tests for resolution etc., they are going to use the same film and/or sensor under the same conditions when comparing samples from a lot or different models.
Of course, and I'd do the same *if I were testing resolution*. But I'm not. I'm talking *utility*. An f/2.8 lens on 35mm film simply is not as *useful* as an f/2.8 on APS-C digital in terms of low light shooting ability, because in order to get a given level of quality (with respect to noise/grain), you'd need a shoot a much lower ISO on film. It's a very simple concept, one that should not really even the slightest bit controversial.

Last edited by Marc Sabatella; 05-13-2010 at 02:33 PM.
05-13-2010, 02:32 PM   #33
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In creating this thread out of the other, I ran into a couple of situations where a given post had some content that was more appropriate for one thread but other content that was more appropriate for the other thread. Unfortunately, I don't have the ability to split posts, or I'd be trying to fix things that way. Right now, I recognize a couple of posts here have some content that really belongs in the other thread, and vice versa. So there's a bit of internal inconsistency in both of these threads.

I feel I'm already in a bit of a no-win situation and don't want to make matters worse. So I propose this: anyone who sees *in one of your own posts in this thread* something you feel belongs back in the other thread, please feel free to edit one of your posts in that other thread (or add a new post) to incorporate the material. Similarly, if there is something in one of your own posts in the other thread you feel belongs here, please feel free to add or edit a post here to incorporate it. Or you can do nothing. All I ask is that you not go in and add more ISO / equivalence talk to the other thread.

As things stand there a couple of loose ends in the other thread that I could see bothering some, and I could see why one would be reluctant to removes one's own comments from that thread unless the person you were reponding to also removed his/her comments. I'll get involved and make that happen if necessary, but let's see if things just work themselves out first. Sorry for any inconvenience.
05-13-2010, 04:40 PM   #34
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QuoteOriginally posted by Marc Sabatella Quote
I might argue that these are inseparable.
I too, but some seem to think differently ("yes DOF changes, but surely the speed doesn't change") and hence I did the two step argumentation.

QuoteOriginally posted by Marc Sabatella Quote
OK, but I still like making *valid* comparisons...
Yes, agreed. My comment wasn't addressed to you.

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