advice on phosphorimager purchase

Tracy Aquilla aquilla at salus.med.uvm.edu
Mon Dec 5 15:57:12 EST 1994


In Article <3bv3ca$25sp at sat.ipp-garching.mpg.de>, krasel at alf.biochem.mpg.de
(Cornelius Krasel) wrote:
>John Brunstein (brunstei at UNIXG.UBC.CA) wrote:
>>       I beg to differ...16 bit D/A conversion DOES NOT in any way 
>> affect the image resolution as compared to 8 or 10 bit, as seems to be 
>> implied in some of the previous posts. What it does is split the recorded 
>> signal intensities into ~16384 'steps' while an 8-bit machine takes the 
>> same range of signal intensities and splits it into 256 'steps'.  This 
>> has no discernable effect on image quality.
>
>Does 16 bit D/A conversion not produce a picture with 2^16 grayshades
>whereas an 8 bit D/A conversion will produce a picture with only 2^8
>grayshades? More grayshades result in better image quality (_not_
>resolution!): you can see the "steps" between two shades of gray with
>2^8 grayshades, but you can't with 2^16 grayshades.
>
>Or am I completely off here?
>
>--Cornelius.
>
>--
>/* Cornelius Krasel, Abt. Lohse, Genzentrum, D-82152 Martinsried, Germany  */
>/* email: krasel at alf.biochem.mpg.de                 fax: +49 89 8578 3795  */
>/* "Science is the game you play with God to find out what His rules are." */

No, I think you are correct here, Cornelius. Image quality and resolution
are not the same thing, although both are important. I use the Bio-Rad
imager (16 bit) and print on a 600 DPI printer. These prints are good enough
to make slides directly. This saves a lot of time and money for me. I see no
advantage to an 8 (or 10) bit system.
    Tracy



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