Digital BW, The Print

Peter De Smidt wrote:
>> Whatever "school of thought" one belongs to it is never a good idea to
>> scan beyond the optical scan capabilities of what ever scanner you are
>> using - 
> Except Sandy King, a very experience photographer and printer, does 
> exactly that.  On his Creo Eversmart he's found that if he scans at a 
> very high interpolated resolution that this scan is better once it's 
> resized back down to the optical resolution of his scanner than if he 
> scans directly at the optical resolution.  The key here is to not follow 
> dogma.  Try things for yourself and see what you get.
> 
> 
Many scanner drivers will skip steps when a lower resolution 
is selected. While the true optical resolution may not be 
more than 2500 PPI you still need to use say 6400 SPI to get 
that 2500 PPI. If you select 3200 SPI and the scanner skips 
steps the optical resolution will drop further and some 
other quality aspects are also affected. What in fact 
happens with high SPI numbers is multi-sampling that can 
also reduce noise and by that extend the dynamic range. 
Selecting an odd resolution like 3350 could force the driver 
to 6400 SPI and downsample that scan to 3350 PPI giving you 
2500 PPI true optical resolution. A trick. And the result 
depends much on the downsampling routine in the driver. So 
selecting the highest SPI number of your scanner and 
downsampling to the true optical resolutopn with a good 
routine in other software isn't a bad idea. Anti-aliasing no 
needed then I guess as it didn't resolve the detail at that 
highest SPI setting anyway. Anti-aliasing would be needed 
for downsampling below the true optical resolution.


-- 
Met vriendelijke groeten,  Ernst


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