Urnst Loc: Brownsville, Texas

We have all heard that small lens apertures cause diffraction, which degrades images. What does that really mean in practice? How much difference does it really make?

rmalarz Loc: Tempe, Arizona

Very good question. It's always good to explore the difference between theory and practice.
--Bob

TriX Loc: Raleigh, NC

Cambridge in Color has a tool to allow you to view an image with different apertures: https://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

Or better yet, use a good photo resolution target and take images from f8 to f22 and compare. It’s easier with a target than a complex scene. I’ve done it and can see the difference, so I try to stay at f11 or larger on ff and f8 on crop, but if a larger DOF is essential to your image and no other way to get it (such as focus stacking), then you just have to live with it.

RightOnPhotography Loc: Quebec,QC

This is an excellent source of information. Thank you for sharing!

CHG_CANON Loc: the Windy City

The best way to detect / disprove diffraction for your specific equipment is to test your specific equipment. You can't look at a single f/22 image and decide if you can detect diffraction. Rather, you need to look at a series of tripod-captured images of exactly the same subject, with consistent exposures, as you walk the lens aperture from f/5.6 through the smallest aperture available for that lens. It doesn't matter much what the subject is, landscape, your house, looking down the street from your house, a single flower, ect.

Just use aperture priority and take 1 to 3 images at each aperture setting. Pull-up those images on your monitor and look at the pixel-level details (100% zoom) at the subject focus and the far background details. As the images progress from f/5.6 through the final images of the test, you should see the out-of-focus details in the distant depth of field initially increasing as the aperture gets smaller from f/5.6. But, over the course of this test, you should see the sharp details reach a plateau and begin to get less sharply focused / fuzzy, both in the distant details and possibly even on the focused subject. Make notes about the diffraction limit for each of your lenses, per camera body. Incorporate this knowledge into your shooting technique.

flyboy61 Loc: The Great American Desert

Bryan Peterson in his books "Understanding Exposure" 3rd and 4th editions, covers the subject very well. On P. 48 of #3, and P. 38 of #4. It is there, no doubt. It is the Physics of light...but in the real world, makes no practical difference, except for endless, useless discussions.

TriX Loc: Raleigh, NC

Here’s the practical difference from a real lens test on one of my lenses on a FF body (would be worse on crop, worse yet on M4/3) that number on the left vertical axis is acuity and the line labeled DLA is diffraction limited aperture, where the difference becomes measurable. Now a 10 or 15% drop in acuity may not seem like much, but it’s the difference between a first rate lens and a run of the mill one, and it doesn’t cost you anything except awareness (or maybe some DOF) to gain that acuity (instead of paying 2-3x for a better lens). That’s why I try to limit myself to f11 on FF and f8 on crop.

Jim Bianco

Like Bryan Peterson says sharp image F/22, don' even think about any other F stop.

camerapapi Loc: Miami, Fl.

"It is the Physics of light...but in the real world, makes no practical difference, except for endless, useless discussions."

I couldn't agree more. When I need f16, I seldom shoot at f22, even with my Olympus cameras I do not hesitate using small apertures. Never an issue as far as I know.

CO

I did my own diffraction test once. I got a circuit board from a computer repair shop. I thought the circuit board would be good for this test because there's a lot of detail. My camera was on a tripod and I took photos at f/11, f/29, and f/36. I created a triptych of the three photos in Photoshop. The upper photo is f/11, the middle photo is f/29, and the bottom photo is f/36. You can see how the image quality is getting softer.

(Download)

CO

Good information. I also try to limit full frame to f/11 and cropped sensor to f/8.

BurghByrd Loc: Pittsburgh

I think DOF should also be part of this discussion. If your subject is in a shallow plane, smaller apertures generally aren't useful anyway. On the other hand if your subject is deep as in a landscape, the smaller apertures will render more DOF and the trade off between increased DOF and possible loss of detail due to diffration is and acceptable compromise.

CHG_CANON Loc: the Windy City

As suggested above, test your specific digital equipment and all your assumptions.

Do you really get any more details in the background past a certain point of smaller apetures? Or, do you really just get a softer image? Let your images and your eyes looking at a 1:1 pixel-level details be the judge, not internet rumors and film-based best practices from the 70s.

BurghByrd Loc: Pittsburgh

And nobody else is allowed to contribute?

imagemeister Loc: mid east Florida