RE: filmscanners: Magnification of light - AND brief density math lesson...

[rafeb <rafeb@channel1.com>]

At 05:28 PM 6/19/01 -0400, Austin wrote:

[rafe b:]
>> On the film scanners I've used, when exposure needs to
>> be messed with at all, it's always a result of an
>> over- or underexposed image.
>
>Not with the Leaf.  They even go out of their way to say to scan at minimum
>exposure of 16ms for everything but chromes, and they say it gives a DRange
>of 3.3, and the only advantage of longer exposure is getting higher DRange
>of 3.7.  Of course, exposure time compensation may help for some
>circumstances.


Well, you tell me, then, why that negative we 
scanned took an hour or more.

Sorry, this all flies in the face of what I 
thought I knew about scanners.  If you're 
going to throw away bits, throw away the LS bits, 
not the MS bits.

That means getting the A/D input as close to 
full-scale as you dare, without actually going over 
the top.

And the only way I know of to do that is to either 
adjust the front-end gain exactly right, or increase 
the CCD exposure.

My preferred method of doing this is: 

1. turn off all software (scanner driver) controls 
   such as levels/curves.
2. adjust exposure to "center" the histogram
3. use software controls to widen the histogram 
   to use, say, 95% of the available codes.
4. Do final tweaks in Photoshop


rafe b.