Diffraction is not a myth and is calculated pretty easily.
However there are several factors not always taken into account that will lighten the visual effect of diffraction, like the gap between photosites (even with microlenses), the implicit interpolation errors by using a bayer array, the anti-aliasing filter...
And of course, downsizing an image reduces the visible effects of diffraction as it is (roughly) like enlarging the pixel areas.
Would be interesting to have a more formal comparison of 100% crops taken at difference apertures with different pixel sizes (a 5D, 1Ds3 etc...) using top lenses.
If you are seeing diffraction in DSLRs at f/4 vs f/5.6, then clearly your test setup is WRONG (misfocusing etc). And I shoot bug macro regularly.
Note that I said "at high magnification". I regularly shoot at f/8 to f/13 when I shoot lifesize, doesn't worry me at all.
In this case, the test images were shot using 450D with MP-E 65mm lens at 5x magnification.
Now at 5x and f/4 the DOF is 0.067mm so the area in focus is very small but you can still see the difference in diffraction between f/4 and f/11 easily.
Is this similar with telephoto? say shooting at 200mm or more? I've never shoot telephoto so I wouldn't know.
I'm in full agreement with Dan that diffraction does not impose a hard cutoff on resolution, rather it's a smooth rolloff which is clear from the formula for it, which states that the amount of blur generated is inversely proportional to the aperture size -- not a hard wall, just a monotonic decrease in resolution in the plane of focus. And as ChrisDM has nicely demonstrated, that can be more than compensated by the increased depth of field rendering more of the image in acceptable focus.
That said, it is fairly easy to see the distinction between f5.6 and f16 in brainiac's OP -- just look at the texture of the wicker chair and the braiding of the blue ropes. The f5.6 images have much more microcontrast and resolution. That resolution difference doesn't mean one should avoid f16 however; it just means that one should realize that f5.6 has higher resolution in the plane of focus, and f16 has larger DOF for a slight loss in resolution at the plane of focus. It's all about tradeoffs, and making the choices that generate the image one desires.
beewee wrote:
Just something to ponder... diffraction is a function of the size of the light sensitive area for each tiny sensor (photosite) that make up a pixel and not pixel size which is a function of how many pixels per given area.
Diffraction does not depend on the proportion of the sensor array that is light sensitive. It is a property of the lens optics, period. The sensor merely records the diffraction-blurred image, to the degree that its resolution allows.
ejmartin wrote:
The sensor merely records the diffraction-blurred image, to the degree that its resolution allows.
My appologies, I should have probably stated "one's ability to detect the effects of diffraction".
But what you said is exactly the point I'm getting at. You can't detect small amounts of diffraction with large photosites. And so far in past years, we haven't really seen any dramatic decrease in the size of photosites even with the large increases in sensor resolution. Of course, that game will take a turn now since, according to canon, they've effectively gone to "gapless microlenses".
beewee wrote:
My appologies, I should have probably stated "one's ability to detect the effects of diffraction".
But what you said is exactly the point I'm getting at. You can't detect small amounts of diffraction with large photosites. And so far in past years, we haven't really seen any dramatic decrease in the size of photosites even with the large increases in sensor resolution. Of course, that game will take a turn now since, according to canon, they've effectively gone to "gapless microlenses".
It's not the size of the photosite that matters for resolution, it's their spacing. Resolution is the precision in detecting a light-to-dark transition, by detecting the light side in one photosite and the dark side (no, not The Dark Side) in the next photosite. So it's the spacing of the photosites that governs the resolution, not the proportion of the photosite's area that is gathering light.
n0b0 wrote:
In this case, the test images were shot using 450D with MP-E 65mm lens at 5x magnification.
Now at 5x and f/4 the DOF is 0.067mm so the area in focus is very small but you can still see the difference in diffraction between f/4 and f/11 easily.
Wait a minute... won't you comparing diffraction at f/4 vs f/5.6? Now you're comparing to f/11?
In any case, if you're truly into LARGE magnification macro, you will never shoot your macro shots at large apertures. As you rightly pointed out, the DOF is just too shallow to be useful. So, using your example to illustrate diffraction is meaningless.
thw2 wrote:
Wait a minute... won't you comparing diffraction at f/4 vs f/5.6? Now you're comparing to f/11?
In any case, if you're truly into LARGE magnification macro, you will never shoot your macro shots at large apertures. As you rightly pointed out, the DOF is just too shallow to be useful. So, using your example to illustrate diffraction is meaningless.
Why do you sound like you're taking my post personally? Have you ever done high magnification macro? The original poster said diffraction is a "storm in a teacup" so I showed him that it is a real problem for macro shooters who want to go above 1:1.
I just posted examples that showed f/4, f/5.6, f/8 and f/11. Point out in my previous post where I said I'm "comparing diffraction at f/4 vs f/5.6" specifically.
As for DOF being too shallow, have you ever heard of focus stacking?
Here is something I shot handheld at 5x mag with a live moving ant. Those "useless examples" of test results gave me the information I needed to balance DOF and diffraction when shooting live subjects outside.
ejmartin wrote:
Diffraction does not depend on the proportion of the sensor array that is light sensitive. It is a property of the lens optics, period. The sensor merely records the diffraction-blurred image, to the degree that its resolution allows.
Quite correct.
Diffraction is a function of the relationship between the physical diameter of the aperture and the distance from the aperture to the imaging plane (as well as the wavelength of the light passing through the aperture).
For a known focal length, the f-stop will let you determine the diameter of the aperture, but not it's distance from the imaging plane. This variable is why some lenses exhibit the effects of diffraction at smaller or larger apertures than the "conventional wisdom" would suggest.
beewee wrote:
Just something to ponder... diffraction is a function of the size of the light sensitive area for each tiny sensor (photosite) that make up a pixel and not pixel size which is a function of how many pixels per given area.
No. Diffraction is unrelated to pixel density or photosite size.
Richard, Thanks for your 'mythbuster' thread. I think the masses need a little more of this sort of practical evidence to reduce the internet parroting that often runs rampant. I frequently shoot at f/16 and f/22 and even if I take a 'backup' shot a stop or two more open, I usually end up using the shot that is stopped down more when final printing.
One diffraction effect that I think people never believe when I mention it...is that diffraction is a lot like Unsharp Mask...and can actually benefit the sharpness of the captured image.
Access wrote:
What does this have to do with real photo-taking? How often are f/16, f/22 or f/32 actually used in actual photography? I have been taking photos digitally for several years (the original 300D) and the only time I used f/16 was for a macro shot which desired maximum depth-of-field. Even f/8 is something I use very rarely in actual photo-taking. It seems like a lot of people are getting all tied up or bent out of shape about sharpness at aperture ranges that are rarely, if ever, used in real or actual photography.
This is so funny - it's shit stirring at it's best
ulrikft wrote:
According to Dofcalculator, everything between 1m and infinity is in focus on a fullframe at 18mm and f/11 (hyperfocal is 0.97cm), I may be stupid, but when in landscape shooting, or even interiour shooting do you need more dof than that? am I missing something?
Edit:
With a 14mm, the hyperfocal is 0.59cm at f/11.
But what size prints do you want. Those hyperfocal distances are based on a 8x10" print, hardly what I'd call a large print. Make 16x20" print and use those numbers and you'll be disappointed.
n0b0 wrote:
Why do you sound like you're taking my post personally?
No I am not taking your post personally.
n0b0 wrote:
Have you ever done high magnification macro? The original poster said diffraction is a "storm in a teacup" so I showed him that it is a real problem for macro shooters who want to go above 1:1.
OK. But this thread is addressed to a large crowd. Very few people shoot super large magnification macro, let alone own the MPE-65. Besides, as has been correctly pointed out already, diffraction has nothing to do with pixel density. High pixel density merely goes to show what has already happened, without affecting diffraction in any way.
But I still find diffraction at f/5.6 quite strange. Diffraction can only happen when the size of the aperture is close to the wavelength of visible light (~ 500 nm).
this is really funny, speaking of difraction. I had someone not want to buy my 100-400IS because he said the test shots he took at f22 were a bit soft... I'm pretty sure that was difraction...
thw2 wrote:
No I am not taking your post personally.
OK. But this thread is addressed to a large crowd. Very few people shoot super large magnification macro, let alone own the MPE-65. Besides, as has been correctly pointed out already, diffraction has nothing to do with pixel density. High pixel density merely goes to show what has already happened, without affecting diffraction in any way.
But I still find diffraction at f/5.6 quite strange. Diffraction can only happen when the size of the aperture is close to the wavelength of visible light (~ 500 nm).
You didn't see my earlier post.
In the macro world it is a real issue and the higher the magnification the smaller the aperture you need to use but you end up with the rule that you need to keep the effective aperture to around f/22 or less, and effective aperture is
f-stop*(M+1)
where M is the magnification. Shoot at 5x you'll need to stick to f/5.6 max otherwise the diffraction induced loss of detail is signifcant. f/16 at 5x is effectively f/96 and the loss of detail is enormous. At dpreview there was an extensive test of this showing indeed @ 5x above f/5.6 the results were apreciably worse, not just soft, but detail was being lost and by f/11 obliterated.
Sorry - I should have said 'storm in a teacup unless you shoot at 5x macro'. If you're a 5x macro shooter you know that special rules apply. The overwhelming majority of lenses are incapable of shooting that close/magnified. Thanks for letting us know that in high magnification macro diffraction is a such a serious limitation - I didn't know that it was such a significant effect.
