Edwin Blenkinsopp writes: > What about multishots (only for still life) images eg the sinar 75h in 4 > shot mode - how does that compare with resolution calculations? > edwin The specs on this back are impressive :) Active sensor size 48.0 x 36.0 mm Sensor resolution 6668 x 4992 pixels, 33.3 million pixels CCD pixel size 7.2 x 7.2 μm the limitations on any digital input (nyquist limits) will always be observed, however the calculations generally applied are to a system like audio, where the limit of accuracy in audio reproduction is half the sampling frequency however that obly applies in digital photos if the subject details are aligned *with* the site receptors or pixels. When any angle is encountered off this axis the smapling accuracy drops to 1/3.. which is why 'jaggies' occur and moire In this article: http://en.wikipedia.org/wiki/Nyquist_frequency under the heading 'The aliasing problem' you can see how phase ambigity as they term it would lead to moire. this occurs with film too, but that is far less often encountered compared to digital where the whole nature of sampling ensures moire is not just likely but inevitable. A more extreme example would be the fan images Andy did some weeks back. resolving power of film isn't restricted by sample frequency :) however as you suggest, ovelaying multiple shots is effectively going to add to the whole of the image data, and when they are blended with the right algorithm, the sampling will be effectively increased and effective limits can be pushed further back - assuming of course that the image sensor isn't capturing *precisely* the same data each time (really really really unlikely!) So I guess if one were prepared to take 4 or so shots of each subject and overlay & blend them, an increase in accurate resolving could be achieved, but if moire creaps in on a frame - and therefore it should in each subsequent frame, that will throw the whole thing into a mess. Thinking on this as I write, if moire even *can* creep in (which it can!) then really you'd need access to the original file information before any demosaicing algorithms were applied to stand a chance of making your overlay/blends work ugh! Maybe this is why it is so much easier for me to spend 5 minutes developing a sheet (or twenty sheets!) of 4x5! :) karl
