Digital BW, The Print

Austin-

Thanks for that.

>
>> Why would the colour of the filter affect the relative intensities of
>> the light hitting the CCD.
>
> Right or wrong, that doesn't have a thing to do with the reason.  It's 
> the
> property of the CCD response/artifacting to different color lights.  
> Each of
> the three lights gives different responses to the CCD and has different
> artifacting.  Red, because it has the highest energy of the three, 
> tends to
> be the fuzziest, simply because of what are called bloom and smear.  
> Bloom
> is basically saturation of the sensing element, smear is basically 
> crosstalk
> between adjacent sensing elements, because of the intensity (this is 
> the
> artifact that PMT scanners do NOT suffer from, as they scan one "spot" 
> at a
> time).  Blue is the next worst, then green is the best...but not 
> always.

I think I understand this but why is the CCD more sensitive to smear 
and bloom associated with red in the absence of blue and green.  That 
is, why would these artifacts appear when the light is filtered and not 
appear when it goes through a ND filter?

I am interested in this because I have recently started 4x5 and since 
my Umax powerlook 1100 is quite soft I'll soon be spending some more 
money on another  scanner.  I'm trying to appreciate how big a 
difference this makes in the overall scheme of things.

--
Kevin Gulstene