From time to time I see questions from photographers trying to figure out exactly which aperture is the “right” one for a particular photograph. Some will go so far as to consult depth of field calculators (or “DOF calculators”) to help them decide whether the should open up a third of a stop from f/11.
There may be times where that sort of precision aperture selection is useful, but in many cases you can make things a lot simpler*, basically selecting from one of three general options:
- If depth of field isn’t a big issue — let’s say you are shooting a relatively flat subject — simply use a “middle of the road” aperture that will be sharp on your lens/camera combination. The old rule of thumb about using f/8 is a decent one to follow here, although cropped sensor shooters might go for something more like f/5.6.
- If you need very deep depth of field, go straight to the smallest aperture you feel comfortable using. On a full frame camera this is likely to be about f/16, while on a cropped sensor camera it might be a bit larger, perhaps in the f/11 or so range. If your need for extra deep depth of field is strong enough that you are willing to give up a small degree of overall image sharpness — which will be invisible in small images anyway — you might even go one stop smaller on some occasions to f/22 on full frame and f/16 on crop.
- If you need to limit depth of field to throw background elements out of focus, simply try the largest aperture that your lens has — but consider stopping down just a bit if you need just a bit more depth of field.
Basically, for most photographs, especially if you have good light and/or are using a tripod, you could probably get away with considering only three apertures in most cases — the “normal” one, the really small one, and the really big one.
- Yes, this is a bit of a simplification, though it really does work in the vast majority of the photographs that most people are making. Clearly things can get a bit more complicated if you are, for example, shooting in very low light or need to deal with moving subjects. In the interest of keeping this “Easy” description easy, I’ll simply acknowledge those possibilities here without elaborating.
G Dan Mitchell is a California photographer and visual opportunist whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
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So that’s why my landscapes on my D3200 crop-frame look soft at f/22…
Indeed! Good to know, yes? Here’s a bit more detailed explanation:
Aperture selection, among other things, allows us to control depth of field (DOF)— the range of distances in front of and behind (if not focused on infinity) the subject that is the center of the plane of focus. By choosing larger apertures (such as f/1.4) we narrow the DOF and can throw subjects beyond (or in front of) the main focus point out of focus, making them soft and diffused. Choosing smaller apertures will increase the DOF, and subjects further behind or in front of the primary subject will be much sharper.
Some photographers make a logical leap from “increasing DOF with small apertures makes more things in the frame look sharp” to “smaller apertures are sharper.” It doesn’t actually work quite that way!
Most lenses do have an aperture range when the overall resolution of the image will be at its best. This point differs among various lenses (and due to other factors) but it will be somewhere between the largest and smallest apertures in most cases. In other words, things can be softer — in somewhat different ways — at both the smaller and larger ends of the aperture range.
At the small aperture end, the image will actually become less sharp as you stop down due to diffraction blur. In other words, if you shoot at an aperture like f/22 on most current cameras, you will increase DOF while youdecrease maximum resolution. Like so many things in life, there is not free lunch!
You will read all sorts of things about which apertures are sharpest, sharp enough, and too soft. In truth, there are a lot of subjective things that have to be balanced: are improvements in focus across the frame more important that maximum resolution in the center? are you willing to give up a bit of ideal resolution in order to obtain more DOF? etc…
A general rule of thumb that I use — based on looking closely at large prints of many photographs — is that if you are trying to get large DOF with good sharpness on a full frame DSLR or similar camera you can feel quite safe shooting at f/16. If you are willing to give up a bit of sharpness to get more DOF, f/22 is an option in some shots.
With smaller sensors the “ideal” point shifts in the direction of somewhat larger apertures. I generally don’t shoot a cropped sensor camera much smaller than f/8 without good reason, though I think you can do quite well at f/11 if need be. I avoid f/16 and have a hard time thinking of many situations in which I would shoot a cropper at f/22.
Dan