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p.1 #3 · p.1 #3 · Prime vs Zoom? [and 24-105 vs 24-70] Dxo reading suggest | |
gdanmitchell wrote:
This is a somewhat complex issue. (You somewhat acknowledge this with the list at the end of your post.)
Let me just take the "primes provide more resolution than zooms" point. In fact, the best primes can generally provide more optical resolution than the best zooms... at least at apertures where the primes are at their best.
But it isn't that simple.
Let's say that I am photographing landscape. I find a subject and I work out an ideal composition — a position defined by my position relative to the subject on three axes (forward/backward, left/right, and up/down) and the subsequent selection of a focal length that frames the composition the way I want. Let's further say that it turns out that my ideal framing after the other axis decisions have been made requires a 35mm focal length.
If I have an excellent 35mm prime in my bag it may provide more (though not a lot more) optical resolution than my best zoom at 35mm. (Or maybe not, depending... but let's say it does.) But at what aperture? If I'm going to photograph at f/11 or f/16, which is not at all unusual for full frame landscape photography, any difference is minimized to the point that it may or not actually be perceptible in even a very large print. So, yes, the prime might be better in this case — where I have the ideal focal length prime in my bag — though the extent of the difference may well be quite (or "vanishingly") small.
However, many of us like to use focal length as a more precise way to control the framing around our ideal composition. Let's say that the ideal framing uses a 41mm focal length. If I use primes, I will pick the prime whose angle of view is a bit larger than what I need for the photograph, with the expectation that I'll crop in post. (Or, I'll compromise my ideal framing, perhaps at the expense of my ideal distance, etc... which is not my preference.) So, let's say I have that 35mm lens in my bag of primes — I'll use that and crop a bit in post to get to what I would get at 41mm with my zoom.
You probably already know where I'm going with this. Assuming I'm using an excellent zoom (which is what I use), the image quality at 41mm is essentially the same as that at 35mm, so I can "crop in camera" with no real image quality loss — I still get to use all the pixels of the sensor, etc. But the photographer using the prime will lose some (or all?) of any resolution advantage that the 35mm prime might have over the zoom, and in some cases the result could end up having less resolution than the zoom.
I can already hear one answer: Simply find a good composition with a 35mm lens or another prime that you have. I have two responses to that idea:
First, that made perfect sense back in the day when virtually everyone only had prime lenses to work with — it was either use the lens you have or don't make the photograph.
Second, in this case we are really just making a choice about which particular compromise we will accept. While it is true that we might make an optical resolution compromise (relative to the most ideal prime result) when we choose to use a zoom, by accepting a less than ideal framing of the subject as a side effect of only using primes one is also compromising. Some my feel differently than I do, but when I consider the truly minimal compromise of image quality (and only in the ideal cases where the prime would be perfect for framing the shot) versus the compromise of not being able to frame my subject in the way I consider ideal, for my part I'll take the zoom over the prime.
I arrived at this perspective over some period of time. I've done this long enough to recall a time when primes were the only option. Long after quite good zooms became available I continued to trust that primes would give me better results. During my transition period I often went out armed with up to nine lenses, of which 3-4 might be zooms and the rest were primes. Over time I began to realize that I was getting equal (or better, if the alternative had been cropping) results from the zooms and I simply found myself using the primes less and less for landscape photography... until I finally (it took years!) realized that for me zooms are simply a better option for this kind of photography. (There are exceptions — for example using TS lenses... but even there you can adapt MF zooms.)
Do I not like primes? That's not the case at all. I own and use a bunch of them... but not because they are optically better but because they sometimes are more functionally useful in certain kinds of photography. For example, I generally prefer primes for street photography because they give me one less option to think about when responding to the rapidly changing street environment. I may also choose them sometimes because I simply need the larger apertures that some of them provide.
Another point of view... :-)
Dan...Show more →
http://www.the-digital-picture.com/Reviews/MTF.aspx?Lens=787&FLI=1&API=3&LensComp=917&APIComp=5&CT=AVG
confirms what you say at f8, there is not much difference between zeiss otus 55 and 24-70 at 50mm.
however at wide open there might be 15% difference.
http://www.the-digital-picture.com/Reviews/MTF.aspx?Lens=787&FLI=1&API=0&LensComp=917&APIComp=2&CT=AVG
And if you cropping a 55 to 41, you have lost 25% of the theorectical resolution or so.
So right again.
But if 35 vs 35, the differences are significant. And don't forget the zeiss mico-contrast
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So I revise my rules of thumb above - If you want to maximize resolution:
1) Use the 5dsr over the 5ds
2) Use the 5dsr over all others
3) If the scene works for one of your high quality primes use it first
4) But otherwise use the best zoom you can get
Again ignoring focus speed, fps, dynamic range, filter that you may or may not have, you can only carry so much etc.
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