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filmscanners: Vuescan long pass mode




----- Original Message -----
From: <EdHamrick@aol.com>
To: <filmscanners@halftone.co.uk>
Sent: Monday, February 05, 2001 1:50 PM
Subject: Re: filmscanners: Re: bit depth and dynamic range



> >  you would want to scan the image twice. Once
> >  to expose for the child and once to expose for the house.
>
> VueScan already does this, and tests have shown that it works well
> with some CCD's but not with others (there's a lot of CCD charge
> bleeding into adjacent pixels with the FS 2710 for example).
>

Are you sure it works on other CCDs ??   It may just not be tested
thoroughly on the other CCDs.   I say that because the amount of bleed over
with the Canon is dependant on the highlight area and the color channel.
Sometimes it looks fine and other times not very good.

For example I used a pin and poked three different size holes in a very dark
Provia 400F slide.   The 2 pixel hole showed no charge bleeding, the 10
pixel hole showed medium charge bleeding and the 40 pixel hole showed a far
amount of bleeding.   In all cases, the red seemed to bleed more than the
green which bled more than the blue.  Also the bleed seems to be only in one
direction.

I've attached 1x, 3x and 6x full resolution raw scan files to show what I
mean.  I cropped out the 2 pixel hole since it didn't change with exposure
and I wanted to keep the file sizes to a minimum.

In any case, hopefully Ed can use these to fine tune the algorithm.

Byron


Attachment: fs2710_bleedtest_6x.jpg
Description: JPEG image

Attachment: fs2710_bleedtest_3x.jpg
Description: JPEG image

Attachment: fs2710_bleedtest_1x.jpg
Description: JPEG image



 




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