Multi shot backs work as follows (there may be detail differences from one manufacturer to another).
The chip has a mosaic filter attached as in one shot backs - ie each pixel has either a red green or blue filter attached to it - normally 2 green to each red and blue.
So each pixel position records only an R,G, or B. In a one shot back the information is then interpolated by taking the value of the other two colours from surrounding pixels to give a full colour image. However good the interpolation algorithms (and they are nowadays very good) they can never get it 100% right - giving rise to a certain amount of fringeing and other artefacts.
For multi shot use, the chip is mounted on (normally) 2 piezo motors. These are small crystals which when subjected to an electrical charge change size by an accurately measurable amount. The chip is moved (normally) in a square pattern in one pixel increments so that each pixel position is able to record R,G and B values thus giving a real - not interpolated, full colour value for each pixel.
(Some earlier backs operated with one piezo motor moving only in a linear manner giving only 4 shots. I don't know if any backs still do this)
In 16 shot mode the incremental movements are less than 1 pixel, therefore creating a greater number of pixel positions over the same physical capture area - ie higher resolution.
Hope that helps.
best ----------------------- Best, Francis Newman Webshot Ltd, UK
On 27 Mar 2004, at 13:38, Brian Yarvin wrote:
Richard and Fellow Listreaders:
I too would like more details, but my reason is more obvious; while I'm a scanning back owner and big fan, I just don't even know what a multi-shot back does. I can imagine ten or fifteen different possibilities and I'm pretty certain all are wrong.
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