Aperture question, re: sharpness

Started Feb 26, 2014 | Questions thread
PhotoPMW Regular Member • Posts: 116
Re: Aperture question, re: sharpness

As a suggestion, why not test your lens? Put the camera on a tripod, 2 second shutter delay, and photograph something with a lot of detail, like a page from a news paper. Take shots from wide open (say, f2.0) to f22. I think you will find that the lens is most sharp around f 3.5 to f 8.0 on MFT.   Wide open won't be too bad.  But you will start to notice some degradation by f11, more by f16 and f22 will be pretty bad. A MFT 25mm lens at f22 has a lens opening of only about 1.1 mm. This is almost like a pin hole camera. This, as others have pointed out, is caused by diffraction, which results from the light scattering as it passes through a narrow opening.  What you get at f22, is greater depth of field.  But I doubt the extra DOF at f22 over, say, f11, is worth the loss of resolution.

Another consideration is image size.  A small Web image or a small print may look fine shot at f22.

If you find yourself trying to get a slow shutter speed in bright light, and you're at your camera's max shutter speed, lowest ISO, and f22, the real solution is to have a 3 to 5 stop neutral density filter and get away from f22.

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Canon EOS 10D
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