Digital BW, The Print

Ernst,

My experience was with an LS2000 so the functions may be different than 
the newer 8000.      I admit I had a lot of trouble understanding 
exactly what  Nikonscan software was doing, when it was applying some 
auto-exposure mojo and why it did it at those times.

The LS2000 manual, from memory, described the gain function as way of 
'increasing exposure'.  I did some testing and arrived at the 
conclusion that it was just moving the histogram but not changing it's 
shape/width.  That may not apply to the 8000 though.

Kevin


On Thursday, January 9, 2003, at 06:55 AM, Ernst Dinkla wrote:

>
> ----- Original Message -----
> From: "Austin Franklin" <darkroom@...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Sent: Wednesday, January 08, 2003 7:23 PM
> Subject: RE: [Digital BW] Scanning and Zone Sys Development.
>
>
>>
>>>>> The Nikon 8000 has analog gain control. I presume that it works
>>>>> the same way
>>>>> as you describe it otherwise why call it "analog gain" control.
>>>>> It will show
>>>>> more noise in the shadows when set to a maximum
>>>>
>>>> Actually, I believe it's misnamed.  This has been discussed with Ed
>>> Hamrick
>>>> and should be in the archives.  It does not change the actual
>>> gain between
>>>> the CCD and the A/D, but the exposure time.  To quote from Ed
>>> Hamrick (who
>>>> wrote ViewScan) from the rec.photo.digital newsgroup:
>>>>
>>>> "The "Analog gain" in the Nikon is a bit misleading.  It's actually
>>>> just the exposure time for each of red, green, blue, and infrared."
>>>>
>>>> Austin
>>>
>>> In what way can one compare both methods ? Is there a difference in 
>>> the
>>> results ?
>>
>> Hi Ernst,
>>
>> Yes, there is a MARKED difference in the results.  The "analog gain" 
>> that
>> Nikon has merely shifts the tones up or down the "scale".  Example:
>>
>>         -
>>       - - -   - -   - -
>>     - - - - - - - - - - -
>> 0 1 2 3 4 5 6 7 8 9101112131415
>>
>> now shift that up:
>>
>>           -
>>         - - -   - -   - -
>>       - - - - - - - - - - -
>> 0 1 2 3 4 5 6 7 8 9101112131415
>>
>> Same curve, just different "values", but all relative values are
> maintained.
>> What it's useful for is getting your entire tonal range within the 
>> range
> of
>> the scanner...but other scanners do that as well with their exposure
>> setting.
>>
>> If the scanner is designed such that it has actual analog gain 
>> between the
>> CCD and A/D, you would EXPAND your analog data, and actually get MORE
> tones:
>>
>>     - - -
>>   - - - - -   - - -     - - -
>> - - - - - - - - - - - - - - - -
>> 0 1 2 3 4 5 6 7 8 9101112131415
>>
>> The limit, of course, is our vision (and noise in the CCD/analog
>> circuitry/AD).  As long as you can get 256 tones out of your data, 
>> and you
>> have tonal "separation" between tones you want to show tonal 
>> separation
>> between...more tones in the image data wouldn't necessarily do you any
> good.
>> Again, I understand the Piezo driver claims to give more tones beyond 
>> what
>> you give it for data, to smooth the tonal transitions.
>>
>> Regards,
>>
>> Austin
>
> Austin, Kevin,
>
> After some excercises with NikonScan and an IT8 slide I'm not so 
> certain
> that it is just a false name for an exposure strength variation.
> When I crop the scan to a small part of the greystep in that image, 
> change
> the analog gain setting so I can get the histogram in the middle,
> then the histogram is stretched to the density range. Of course it 
> still can
> be a digital stretching that is performed and not an A/D stretching 
> but it
> isn't a simple exposure change either. Still a false term if it is not 
> done
> at the A/D stage.
>
> What is interesting though is that it will not stretch any crop and 
> with
> "positive" negative scanning the redraw button will more often (but not
> always) initiate a new reading scan instead of picking the data from 
> the
> preview. That could mean that NikonScan is behaving more intelligent 
> than
> expected. My guess is that it could use true analog gain but checks 
> what it
> actually has to offer in dynamic range to make that worthwhile. That 
> makes
> this function less transparent but still very useful. It also has the 
> logic
> of the comments I made before on the usefulness of analoge gain in CCD 
> film
> scanners, most of the time there's not enough dynamic range.
>
> What I write is based on 'dry' scans, I didn't measure the RGB values 
> in
> scanned images etc, just looking at the histogram changes.
> Disappointment is still possible.
>
> Ernst
>
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