Is the "after f/11 diffraction screws things up" rule BS?

[djotaku]

Everywhere I go where there are amateurs (including me) giving advice (this forum, blogs, etc) people say that if you go past f/11 you get diffraction and things get blurrier so what's the point. In other words, I often see the advice that if you shoot at f/2.8 or your lens' max aperture it won't be that good. The sweet spot is one stop more. And don't go past f/8 or f/11 because diffraction comes into play.

HOWEVER, when I read books by professionals such as Scott Kelby, another author whose book I don't have in front of me, Ansel Adams, etc they often advocate going to f/16 or even (as in Scott Kelby Digital Photography book vol 2) f/22 for more sharpness. So why the discrepancy?

As you know - there's a lot of BS that gets spread on the Internet so did this diffraction thing spread that way? Alternately, could it be that diffraction only affects the crappy cameras that we have and if you have a Canon 1D or the Nikon equivalent then diffraction doesn't affect it? (I already know that full frame cameras have a different dof characteristic than crop frame cameras)

I wanted to share this info/start this debate because I've seen it hundreds of times here where we tell neophyte photographers that there's no point going beyond f/8 or f/11 and if the pros are going past that - perhaps that is (along with experience) one of the reasons their photos are a whole level better than ours.

[sk66]

Yes, it's bunk.
It depends on a lot of things. As important as the lens is the camera sensor size. Another significant factor is final image (print) size.

See here for more

[Doug Pardee]

Originally Posted by djotaku

when I read books by professionals such as Scott Kelby, another author whose book I don't have in front of me, Ansel Adams, etc they often advocate going to f/16 or even (as in Scott Kelby Digital Photography book vol 2) f/22 for more sharpness. So why the discrepancy?

The biggest discrepancy is format size (film size, sensor size, whatever).

f/11 on an APS-C camera has the same sharpness effects (DoF and diffraction) as f/18 on the 35mm camera that many books are written for. It has the same sharpness effects as an Ansel Adams 8x10 camera at f/56 or so.

At that aperture, you're close to where most people feel that diffraction isn't much of a problem. Adams considered f/64 to be an excellent choice for 8x10 photography, and f/16 is widely used in 35mm photography.

In the end, it's up to you to decide how much diffraction you can deal with. It's a simple process to take a series of shots of a subject with some fine detail, one shot at each f-stop, and then look at the results and see what you think. For me, from my tests, f/11 is not a problem, but f/14 is starting to push it on my 1.6x DSLR.

(Be sure to use a tripod or have your camera sitting on something stable for those tests. You don't want camera shake due to low shutter speed at high f-numbers to confound the results.)

[vandergus]

Sounds like it's time for some personal experimentation. Take you camera out with a couple lenses and make a set of shots where only the aperture varies (adjusting shutter speed to keep exposure constant). Get them back on your computer and examine them up close. Then makes some prints and see if the differences are still noticeable.

Personal experience always trumps speculation.

[kencaleno]

No BS; It's fact- Film has better resolving qualities than digital,and that is why Ansel Adams et al,recomended using F22 etc., What happens is when you get smaller than F11 with digital, diffraction is barely noticeable-but, when you get down to F22,32,etc., diffraction will effect sharpness to some degree. So you need to decide which is most important-great depth of field, or image sharpness.

Diffraction is caused by light rays forcing themselves through a very small aperture, causing a tangle, and because of the large area of diaphragm showing rays bounce around the lens elements causing more confusion-effectively softness; and sensors can't handle this as well as film can.

Regards, Ken

[vandergus]

Diffraction is caused by light rays forcing themselves through a very small aperture, causing a tangle, and because of the large area of diaphragm showing rays bounce around the lens elements causing more confusion-effectively softness; and sensors can't handle this as well as film can.

I hate it when my light gets all tangled and confused.

[OsmosisStudios]

I've found that with the majority of my lenses, f/11-f/16 is the smallest I'd want to go.

[wulf]

Originally Posted by vandergus

Sounds like it's time for some personal experimentation. Take you camera out with a couple lenses and make a set of shots where only the aperture varies (adjusting shutter speed to keep exposure constant). Get them back on your computer and examine them up close. Then makes some prints and see if the differences are still noticeable.

That's the best way. Use the web to open your eyes to new ideas but don't expect it to do your homework for you (*) because you won't learn nearly as much.

Wulf

(*) ... metaphorically speaking. I'm not suggesting djotaku is trying to cheat on a class assignment although people have tried that in the past!

[Benji]

As I've said lots of times the internet is a great place to gather misinformation. For example didja know that you can get more DOF by opening up your aperture? Or that you MUST use the manufacturers suggested shutter speed ONLY to synch your flash lit images? How about a large silver reflector held in front of your subject redirecting direct sunshine is done "all the time" by professionals and it won't cause the subject to squint? I've read all of these (at least two of them here at DPS) and many more on the 'net and they were presented as the gospel truth.

Benji

[wulf]

Since we had got to a point where people were having to use a dictionary to look up the insults, I decided it was time to do some tidying up and put things back on track.

The question is whether there is any truth in the statement that diffraction becomes a major issue when stopping down past f/11. Illustrated answers are very welcome; bickering is not.

Wulf