"Christian Skofteland" writes:
>around with the B&W negatives. My scanner only allows 1500 ppi resolution
on
>B&W negatives but it goes up to 2400 for color negatives. Is there
anything
>wrong with scanning the B&W as color and converting the scan to grey-scale?
>The results look good and the higher resolution scans are more to my
liking.
The short answer is that if the scans look better to you, then do them that
way.
However, the long answer has to do with the way the scanner works. If it
of a typical design where it uses a color mask over the CCD, then you are
not getting the resolution you think you are with a color scan. That's
because when the scanner performs a color scan, the hardware returns an
(say) 8-bit grayscale image, but different pixels are masked by different
color masks, and therefore reprenet only a single R, G or B color. To
create a color image, where each pixel represents a R, G and B value, it has
to take the colors that are absent at that pixel location and borrow values
for them from adjacent pixels.
This means that, for example (Bayer), the red plane of the image is
actually represented by 1/4 of the pixels of the scan. The red values for
the other 3/4 pixels of the scan are derived by blending adjacent red
pixels. Ditto for blue layer. Green layer is an odd beast using the Bayer
mask pattern in that 1/2 the scanned pixel values have a green mask, so it
actually has more detail than the rest of the layers.
Now, when you then flatten the image back to grayscale, you've blurred
adjacent pixels by using a color scan.
Given that it is a B&W negative, so have no color info to get in the way,
the scaner could do something like perform a color scan and then just forget
that the pixels had R, G or B masks over them. Perform some intensity
adjustment to counter the light response of the CCD under the mask and
you've got an actual B&W image. Perhaps this is what it is doing when it
gives you a 1500ppi B&W scan?
later,
patbob ([EMAIL PROTECTED])
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