Sensor size and diffraction.

ProfHankD wrote:

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).

Quite correct, and the cleaner, rounder opening [usually matt black as well] may well reduce flare as compared to the metal polyhedral openings of adjustable apertures.

Certainly the familiar "starburst" flare we see in most cameras is very much reduced in my Casio ZR700 as compared to my Panasonic ZS25. [the Casio ZR700, 800 & 850 have some very interesting "tricks" such as in-camera macro-focus "stacking" achieved through very rapid burst shooting and dual-core processing]. A visit to the Casio forum may interest you.

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.

Yes, again, although I can't really agree RE: the fully automatic modes which usually go to tinier apertures too quickly.

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.

This post is one of several versions which I have used over the years, trying to help new users on the Panasonic Compact Camera forum. Unfortunately, so much of the literature is hung up on larger format that the considerations of diffraction limits are rarely discussed and, indeed, many "authorities" do not understand it themselves.

Thank you for your input.

I actually just "parked" this post in this fairly inactive forum to check some editing I'd done without confusing the issue on the panasonic forum in case there were typos, and decided to leave it here