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scanning film with sd quattro

Started Mar 11, 2017 | Questions thread
OP Artemka New Member • Posts: 6
Re: scanning film with sd quattro

The only way I tested some b/w shots was via dcraw. There is a command line option to generate un-demosaic linear tiff from raw. You get then a gray linear image with full resolution but with the filter effects of the bayer filter in front of the sensor,

Then you have to equalize the gray 2x2 underlying pattern which is the result of your exposure light source and the dye filters. To construct the equlization you have to exposure a master image with about 18%. This master image must be inverted so that you get 0.18/image_value. The inverted master image have be multiplied with every tiff to get the color pattern out of the gray image.

The link below describe the usage for a custom demosaic but the construction is similar.

http://therefractedlight.blogspot.de/2014/04/cook-your-own-raw-files-part-3-demosaic.html

The difference is that the author construct a bayer pattern image where you need an inverted equalization image. The second step by the author is the custom demosaic which is not needed for b/w. The layer operation is done PS but RT is also possible.

An issue is that hot pixels where not removed up to now. Possible that dcraw have an option to interpolate hot pixels and not demosaic at the same time. This what I remember from more than 2 years ago.

This is new for me and there's quite a lot to soak in. I'll get a coffee and get started.

Much obliged to you (and the others in this thread) for kindly sharing your knowledge.

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