View Full Version : Ian's DP Now Article on Diffraction

2nd February 2011, 03:45 PM

Has anyone read Ian's article on diffraction over on DP Now? I did and I was shocked! Like most people, I assume, I have heard of diffraction and knew that past a certain aperture images would become progressively less sharp due to softness caused by diffraction. On 4/3rd's I've always assumed that this would be at f11 or above and that using f8 would be OK. For this reason, I hardly ever use f11.

Ian's article shows crops from an E5 with a 35-100 f2 lens. It clearly shows that even at f8, there is some softening due to diffraction. That was a surprise. At f11 the softening is clearly visible.

However, what shocked me the most was the table at the bottom of the article that gave the diffraction limit for different sensors with varying pixel counts. What shocked me was the suggestion that for a 16 MP 4/3rd sensor, diffraction would kick in not at f8 but at f5.6.

I'm wondering whether this is the reason why Olympus haven't gone past 12 MP on 4/3rd's? I also wonder where it leaves Panasonic's 16 MP sensor?

I also noted that on a full frame 12 MP camera, diffraction kicks on at f13 and f11 on a 24 MP camera.

Has anyone else read the article?. If so, what do you think? Read it here:


Kiwi Paul
2nd February 2011, 04:04 PM
Yes I read it too, it was interesting. Certainly having a diffraction starting at f5.6 on 4/3 with a 16Mp sensor is a limitation although that still corresponds to an equivalent DOF as f11 on full frame so it's not as bad as it sounds but may well be why Oly has decided to stick to 12Mp.
I think in real terms using anything up to f9.5 is not a concern, I use f9.5 often when photographing landscapes where I want max DOF, the photos are sharp and crisp.


David M
2nd February 2011, 11:15 PM
There's already a thread discussing the article;


David Morison
3rd February 2011, 07:20 AM
I think there is a danger of getting to hung up with numbers and pixels. It must depend on what you need from your subject, how much you want to crop/enlarge and whether technical or artistic factors are to prevail. I took this image on a Leica 14-150mm @14mm with an aperture of f20 to gain max DoF. If there is any loss of sharpness due to diffraction then I hadn't noticed it and it would not anyhow detract from the finished picture for me. I have printed this to A3 without concern. (appologies image posted before)

http://e-group.uk.net/gallery/data/500/Blue-Connemara.jpg (http://e-group.uk.net/gallery/showphoto.php/photo/29855)


Jim Ford
3rd February 2011, 02:45 PM
Has anyone else read the article?. If so, what do you think? Read it here:


Hmm, is that moire I see in the window net curtains? Moire has been reported on E5s because of the 'weaker' anti-alias filter.


6th February 2011, 07:09 PM
I think the issue might be a bit overrated. However, we shouldn't forget how equivalence works for us. F11 is the same for us as F22 on full frame so we're already getting plenty of depth of field at that point (and the image should respond well to sharpening if the effect of diffraction is visible), especially if shooting with a wider focal length.