> Unless you scan with the maximal resolution (10/12 bit) and no LUT,
> you cannot easlily reconstruct the dust-image from the
> infrared channel . That'a why I think the conversion from Inrared
> to "dust" should be done by the backend. It is a very scanner
> dependent operation as it depends a lot on the
> light source and CCD sensitivity for the different wavelengths.
The algorithm is not scanner dependent at all. Only the parameters
vary (but they vary with filmtype too). I still think it's possible
that the parameters can be autoguessed by minimizing some sort of
correlation between the channels. You have access to a few million
data points, so what would stop you.
> Maybe I'll add a raw format option that writes all data
> without transformation to a 64Bit image (4*16) to
> be used by a program that can do the Coolscan specific dust-removal
> and which can apply the LUT afterwards.
I'd be much obliged, this is exactly what I want.
> This type of data-flow is basically optimized for speed - meaning
> you don't have to wait on the scanner and the scanner doesnt
> have to wait for the dust removal -
My upcoming new frontend does all processing on the fly with priority
to reading the scan data, meaning both scanner and CPU will work at
full speed. This would be another reason to at least have the option
to do defect removal in the frontend.
> it is not because I hope
> there will be a general way to treat these images.
I gather you haven't had too much luck with it yet but damnit it must
be possible!
> While the 4*4 transformation can be done "on the fly" pixel per pixel
> without having all the image available, the dustremoval needs
> the whole image (or parts of it) to do spacial interpolation.
You don't really need the whole image, a few scanlines are sufficient
to do the interpolation (I have done this once). So it is possible to
do on the fly too. You just use already interpolated pixels for
interpolating the lower defects.
-- -- Ewald
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