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Sensor size and diffraction.

Started Jan 2, 2016 | Discussions thread
ProfHankD
ProfHankD Veteran Member • Posts: 9,147
Re: Sensor size and diffraction.
1

Erik Ohlson wrote:

"A" mode is the best for any of the pocket zooms, by any manufacturer.

It's technical - physics, actually. The sensor is quite small, therefor the lens must have a very short focal length - usually about 4.3mm (that is approximately 1/3inch).

Actually, most small-sensor cameras simply don't have an aperture to adjust when the sensor is already at the diffraction limit -- this is why so many Canon PowerShots have a built-in ND filter (which is motor driven to go in/out of the optical path).

The ones that have an adjustable aperture iris generally have a long enough zoom range so that the smaller apertures are usable at least at the longer focal lengths. In fact, the fully automatic program modes will generally do the right thing in terms of avoiding the potentially worthless combinations of focal length and aperture.

However, the principle is correct, and especially when using fully manual lenses adapted to a smaller-than-expected-film-size sensor camera (Pentax Q, Nikon 1, etc.), the smaller apertures (higher f/numbers) should be avoided.

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