gdanmitchell
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 p.5 #8 · Focus Beyond Infinity | |
ruthenium wrote:
Dan, diffraction is one of many considerations in photography - far from being the top consideration. I expect very few photographers are obsessed about diffraction.
Changing the aperture is a 100% practical decision, as you correctly noted. The problem is that an average photographer is guided by experience and intuition, but they are very rarely guided by exact knowledge. Jack Hogan actually studied the effects of changing the aperture in three different scenarios. The reason he came to the conclusion that "for me, it seems that I will no longer be stopping down past f/11" was that he found no benefit to this. I am inclined to believe him.
When you say "I'll use f/16 or sometimes f/22 on a full frame system" - my immediate question and concern is whether you BELIEVE that this should improve the image (vs. f/11 or f/8, for example), or you have carefully tested the outcomes and can prove this with the images to show me that your strategy actually works better? This is not a personal comment in any way. The modern world is drowning in misinformation and misunderstandings, and my belief is that 99.999% of photographers may believe in something about photography that is verifiably not correct. Like you already mentioned this about what some believe about diffraction on micro-four-thirds systems. Similarly, I confidently expect that too many photographers genuinely believe that an f/2.8 lens is as "fast" on FF as in front of a sensor of a different size - just to give an example.
Some photographers tend to be more interested in an in-depth understanding of the technology. Others dismiss this interest entirely as useless, and take pride in the wealth of their practical knowledge and experience. It makes sense to respect both groups and listen to both groups, however, ultimately we need to be aware of the fact that the field of photography is full of misconcepts, myths. and ideas not rooted in science.
My main concern about closing the aperture is the about the loss of light, more than about the effect of diffraction. Unlike the "proper" landscape photographers who shoot from a tripod, I almost always shoot hand-held. Thus, retaining a reasonable shutter speed at the base ISO, or as close to the base ISO as the circumstances permit, is one of my usual top technical considerations (outside of the composition). ...Show more →
I’m fortunate enough to have a 44” printer, so I can test and have tested plenty of large prints against the theories. It also helps to have viewed a whole lot of great photographic prints by a whole lot of great (as in “they are in galleries and museums”) photographers over the years. The fact is that that tiny final increment of sharpness that some are looking for turns out to matter a lot less than they expect.
(I encourage people to actually to to an exhibit and look at the prints of photographs that you regard as great, and to do so as closely as you possibly can. You’ll virtually always find that they don’t have the “pin sharp at any size” qualty that folks imagine they’ll have. I recall seeing this years ago in Ansel Adams prints. I really recall “getting it” at a SFMoMA exhibit of the gigantic prints of Jeff Wall — they are stunning when viewed as we normally do, but if you get nose-length close… Same with the famous Avedon “American West” portraits, which I’ve seen in person a couple of times — utterly stunning, huge prints…)
My point is not that diffraction has no effect on the sharpness of photographs at f/16, for example. Objectively speaking, it absolutely must — there’s no getting around that law of optics with the gear we use. However, two other things are also true, and it is critical (and freeing, for those obsessed with “perfect apertures”) to understand them.
1. While, for example, f/11 or f/16 is undoubtedly objectively less sharp than your diffraction-limited aperture, the difference in a real photographic print at size (or an equivalent electronic presentation) is often insignificant or invisible in any way that is meaningful to observers. In many case, if you looked at a crop from a f/8 and a f/16 shot that featured something in the plane of optimal focus, you’d be hard pressed to figure out which is which.
2. In many cases, other needs trump the “best aperture” sharpness. If you need a bit more DOF, it doesn’t mater than stuff in the plane of focus is a tiny bit less sharp — but still very sharp — since you are more concerned with things a little outside that plane. The inverse of that is that f/1.4 or f/1.2 or whatever large aperture you select gains you no sharpness and will likely lose a bit of it for other optical reason… but that the overall result may e better if the use of narrow DOF is important to your photograph.
And, yes, I have very much tested these things. I’ve gone so far as to set a camera on a tripod, prefocus, turn of AF, and do a series of aV mode images at each whole aperture and then compare side-by-side on screen and in prints.
In the end, I operate by those three rules that I listed earlier.
1. If DOF isn’t an issue (I don’t want to narrow or widen it) I’ll just shoot at an aperture that is somewhere in the range of the lens’s best performance and the diffraction-limited aperture because… why not?
2. If I need to limit DOF for creative reasons, I’ll open up as much as I need to in order to get the effect I desire.
3. If I need more DOF I’ll stop down as much as makes sense with the system I’m using and the subject I’m shooting. (If that can’t be achieved by using a small aperture, I’ll resort to focus blending techniques.)
On full frame, my typical default (which varies by lens) is around f/8. On APS-C my default is around f/5.6. On full frame I don’t worry at all about f/11, and I’ll use f/16 if needed without worrying much. On rarer occasions when I maximizing DOF is import and I ma use f/22. On APS-C I move that scale rough aperture larger — e.g. I am fine with f/8, may use f/11 without much concern if I need to, and only rarely use f/16.
One of the great things about digital photography technology is that it is so easy to actually test these things yourself — you don’t have to rely on what what you read or what others tell you. You can listen to them and then test what they say to see if it actually is true, if it makes a difference, and how large that difference is.
I’ll turn your 99.999% of photographers analogy on ts head for a moment. Here’s the danger. After reading a truth (for example, that there’s more diffraction blur at apertures larger than the diffraction-limited aperture), too many people take that one fact and base everything on it while failing to recognize that it is just one data point to consider when making photographs. We see that category of error all the time in photography forums: the person who learns that camera A has more DR than camera B and concludes that Camera A is the best. The person who learns that Camera C has faster burst more than Camera D and decides that Camera C is the best camera. The person who learns that format E can capture more detail than Format F and concludes that Format E is the best format. And on and on — repeat with the system with the “best” noise handling, the best AF, the best “whatever.” It is too easy to let this stuff become both obsessive and one-dimensional.
And, of course, those who decide that photography is all about technical specs and who lose track of what actually makes a photograph great…
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