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Possible Duplicates:
What is a “diffraction limit”?
Why are my photos taken at f/11 less sharp than those taken at a wider aperture?

I have made 3 landscape pictures with f/12, f/22 and f/32. Shutter speed and ISO are almost same, but last one has a lot of blur and is very pale. Why this happen? My purpose was to get maximal DOF.

Details: Nikon d5100, 18-55 kit

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yura
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  • If you provide the pictures, it might be easier to diagnose what is happening. – Dylansq May 17 '12 at 03:16
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    You are very confused, see the question as suggested duplicate. F/22 is a very small aperture and causes your camera to pass beyond its diffraction limit, causing everything to become blurry. There should be very little reason to shoot beyond F/11 with such a DSLR. If you need longer shutter-speeds, use a quality ND filter. – Itai May 17 '12 at 03:29
  • See also http://photo.stackexchange.com/questions/20430/why-are-my-photos-taken-at-f-11-less-sharp-than-those-taken-at-a-wider-aperture – Itai May 17 '12 at 03:31
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    FYI: for the Nikon D5100 + 18-55mm kit lens, the lens only goes up to f22. – Viv May 17 '12 at 03:44
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    Also if your aperture changes, your shutter speed / ISO should change to maintain the same exposure (Assuming that you are not in manual mode). Did you use a tripod? – Viv May 17 '12 at 03:51
  • @Itai My purpose was to get maximal DOF possible with my camera, not shutter speed... So you suggest to use F/12 as limit for my aperture and DOF? – yura May 17 '12 at 04:00
  • @Vivek for 18mm max is 22 but for 55m it is 36

    Yes I have used tripod and was in manual mode

     – yura May 17 '12 at 04:01
  • Oh yes. F/13 actually should be the diffraction limit for your camera. Beyond that, everything gets blurry. – Itai May 17 '12 at 04:11
  • @drewbenn yes, I understood these factors. But blurry image with big F number seems invariant on all pictures, with small ISO~250 and speed 1/400. So I it seems diffraction limit really matters – yura May 17 '12 at 06:03
  • Another point to remember is that a very big aperture is one that has a small number. F/1.4 is very very big aperture, F/22 is a tiny aperture, not the other way round. :) – i-CONICA May 17 '12 at 12:46

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Without wishing to get into detail - the short answer to your question is diffraction. This happens at smaller apertures, usually when you get above f/16 to f/22 etc, and the extent to which it occurs depends on the optical quality of the lens used. In your case, the 18-55mm kit lens which is a mass-produced cheap kit lens will show this problem moreso than say a fixed focal length prime lens.

You can achieve good depth of field with a more modest aperture such as f/14. There is rarely if ever good cause to go all the way up to f/22.

Mike
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