Real world diffraction tests, 40D.

If you want to learn someting about diffraction you are invited to do some reading on the following thread.

You will see that it is simple and not theorical but verry practical and real.

http://www.cambridgein​colour.com …ffraction-photography.htm

Diffraction has happened before the image gets to the sensor, whether film or CMOS - pixels just record whatever diffraction they "see". Pixels don't affect diffraction The tutorial linked above shows what happens when different cameras, with different size pixels are moused over. The Airy disk size stays the same at a given aperture but the gridlines change.

The number of pixels might influence how much you enlarge the image to view or print and whether a fixed amount of diffraction blur is visible to the eye.

As for real world.. yes its real world if you shoot product shots and need max DOF. It may not be real world to you if all you shoot are landscapes at infinity focus. It's also a real world test b/c unlike the link above it does not involve a bunch of math and figures to put into some calculator to give you another number that means what exactly in the real world?? I have noticed in real world shots eyelashes tend to mush up a bit at f16 compared to f8... but its very pixel peepish and never shows on a print. But it is there, ever so slightly.

Another reason its real world? Well They are slightly sharpened, as someone mentioned trying to blow the test out of the water. The bottom line is I dont print raw files unsharpened. So I honestly dont care if sharpening hides some diffraction.. because I ALWAYS SHARPEN.

Keep in mind that the crop is about a 1" square on a 750ml Jager bottle.

Also note that this was not setup to be a wide open lens test. This crop is slightly off center and I did not check to make sure the focal plane would be exactly flat on the bottle. Some of the softness you see at f2.8 could be out of focus. As I have gotten many great very sharp keepers at f2 with this lens.

I would like to see some tests similar with the 50D b/c I really do not want to lose anymore sharpness at f16. That's one of my reasons for not upgrading.

Again.. I did the tests to see the effects with my camera and how it might affect me. I shared the results for those to either use for their benefit or not. When I get bored and have nothing of value to shoot, its a good way to polish off a bottle of Jager and do some shooting. Either way, I dont care, and if you dont think my method of testing helps you learn anything then hit the back button and carry on. I got from what I wanted from it and that was the goal. I have looked at that diffraction calculator many times and it told me my images should suck at f16, I want to see what suck actually looks like in an image.

Can I help? I have what's listed in my sig. What sort of shots do you want? Only prob is suns just about to go down here, and I do have to work tomorrow, so maybe tomorrow afternoon

FlexiPack wrote in post #8266447
Good and interesting test. I'd be really interested to see this test done with a 50D/500D to see how much diffraction is an issue with the higher MP. It should be a bit more noticeble but i'm curious how much.

Diffraction test - 50D

There you go, saves me some work

So basically what I get from all of this is yes, there is a thing called diffraction that does affect images. Is it critical? Not for me. Honestly in all the tests I have seen so far, I still find the wide open shots worse if not the same as necked right down, but that's just me... Having said all that, I don't think I have ever gone down past 16 anyway. Maybe as my skills increase I may find my theories change a little. Interesting reading though.

pixelbasher,

That's exactly my own take on this whole thing as well. I often use f/22 for my landscapes and while I'm only using a 30D, have never had any problems.