At wide aperture you are depending on the precision of the whole area of the lens. The larger the lens the more difficult it is to configure them to "diffraction limited" specifications. (This means that the lens cannot resolve any more detail than is possible by the physics of light itself.) So there's always a trade-off going on. Larger diameter lenses *can* resolve more detail but *only* if they are ground to absolute precision. This is why DSLR glass invariably produces softer images at wider apertures, just due to their size.Now you have another thing at play. At wider apertures you have to focus much more precisely. Your DOF is not as forgiving at wider apertures. I suspect that your wide-aperture images might be suffering from mis-focus more than poorly ground lenses. At wide aperture you have to depend on precision focusing and precision ground optics. At smaller apertures you hit the other wall and you delve into the area of diffraction limitations. Wider aperture can provide sharper images if all things are going in your favor. There's always a sweet-spot somewhere in the middle of any lens design where aperture (for resolution and lens quality) benefits more than the diffraction limitations and deep DOF at smaller apertures.The nice thing about the smaller P&S lenses is that it is much easier to grind them to precision curvatures. So that sweet-spot can span a wide(r) range of f/stops. Whereas in larger lenses for DSLRs there's usually only one f/stop where they get the best images.
I'm reading some articles on Wikipedia, but i would like more material to study from.
then try to reason-out why they did or did not work for your intended purposes.
I had the opportunity to try out Albest'st long exposure feature on my S3 IS recently. It was at a site with very a dark sky and no moon. The camera was mounted on a Meade ETX-125EC telescope and roughly aligned so it would minimise the star trails. ...I can't wait to try out my wifes A560 which is a much smaller and lighter camera now that there is firmware for it. Thanks to all who have been involved in developing the CHDK firmware, being one who tries to do "more with less", it has made all sorts of previously impossible or horrendously expensive ideas now achieveable.
Started by Woodsman Creative Uses of CHDK
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Started by Davo « 1 2 3 4 » Creative Uses of CHDK
