Re: Blue CCD Banding: A Little Test

[Arthur Entlich <artistic-1@xxxxxxx>]

Hi Phil,

Very interesting slant on this issue...

This may seem either silly or obvious or both.

If a scanner could be optimized for just transparency work could a 
better film scanner result?

I shoot almost no neg film, personally.  If a manufacturer made a 
scanner that was optimized for slides only, and as a result made a much 
more neg scan,  I could live with it, or buy a cheap scanner that was 
optimized for negs should I require it.  I would be willing to give up 
scanning color negs completely for a 20% improvement in slides scanning.

I wonder if there are others who would make the same decision if it was 
an option?

Art


Phil.Lippincott wrote:

> Paul and Friends
> 
>    The blue CCD channel is generally the weakest of the three color channels for
> the sensor.  On especially negative film the blue channel is the densest or
> darkest channel.  Thus there is a conflict between the least sensitive channel
> needing to scan the most difficult darkest film densities on negative films.
> This both why a yellow posterization cast exists on a lot of CCD scanning of
> negatives and why the scanner engineers like to turn up the blue channel gain,
> integration time and sensitivity in blue.  Yet if they turn up the sensitivity
> it also pushes the CCD into a noise condition of over modulation and yes banding
> in the blue channel distinguishable from the others.  This whole process is a
> catch 22 which is very frustrating to CCD scanner designers, engineers and
> software developers.  We need better CCDs or PMT (photo multiplier) / drum
> scanners to avoid these issues.
> 
> Phil Lippincott
> www.aztek.com
> 
> "Paul D. DeRocco" wrote:
> 
> 
>>I don't think it could be, because then it wouldn't be able to do superfine
>>mode with a single line. It sounds like it's three lines, each of which has
>>RGB sensors, whose only purpose is to be able to capture three scan lines at
>>a time. I don't think the fact that there are three lines has anything to do
>>with the fact that there are three primary colors--they could have used a
>>four-line CCD and made it four times as fast as superfine mode.
>>
>>Or maybe I'm missing something.
>>
>>--
>


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