Re: [APML] More SS4000 scanning questions

[Jerry Lodriguss <jerryapml@astropix.com>]

>1. I notice so far in his examples, that he has color management 'off'.
>Is there a reason for this?

That's because they were scanned with a scanner that did not support color 
management.  You can assign sRGB to those scans.




>2. When I scan and save 'raw' images, the dialog indicates that it is a
>12 bit image. I had hoped for 16 bits. What goes?


The scanner is probably only 12 bits native tonal resolution (tonal, not 
spatial).  But a 12 bit file has to be saved as a 16 bit file because you 
can only work in 8 bits or 16 bits, not something in between.




>3. To save time when scanning lately, I have not been doing pre-scans.
>I simply do the full res scan and go to the next one? Is this OK, as
>I'm scanning and saving untouched 'raw' images?

If all of the images are on the same roll, then you should do one pre-scan 
for the first one to calibrate the scanner. Depending on the scanner, you 
should be able to scan all the rest with those settings.

True raw scans can be difficult to work with because they will be very very 
dark and low contrast. The histogram will be almost all the way to the left 
also. You HAVE to work with these files in a higher bit depth than 8 bits.


>4. I've asked this before and the answer made sense. For 35mm color
>negative film, is a scan setting higher than 2700 dpi useful? I had
>someone tell me in an off-topic discussion on the Losmandy group that I
>should be scanning at the highest resolution, 4000dpi in this case.

If you have a scanner with 4000 ppi of true optical resolution, then you 
can scan at 4000ppi.  If your scanner only has 2700ppi of true optical res, 
then scan at that. Don't interpolate up in the scanner software.





>5. In a related question, should slide film (E200) be scanned higher
>than 2700dpi, seeing as it has higher contrast?

It's not so much as question of higher contrast as a matter of the film 
being able to record higher resolution. If you have poor tracking, poor 
seeing, poor guiding, poor focus, and mushy large stars, then you can scan 
at a lower ppi because there just isn't that much information on the film. 
IF you have killer seeing, focus, guiding, and a scope that can produce 
tiny stars, then you need to scan at a higher true optical resolution to 
digitize all of the info on the film.  If you have crap images on techpan, 
scanning at 4000ppi won't help and is not necessary.


Jerry





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