Digital BW, The Print

On Thursday, May 29, 2003, at 08:23  AM, Austin Franklin wrote:

> Hi Kevin,
>
>> I think that the density range of virtually all
>> silver negatives that you would want to scan are within the range that
>> a current model film scanner can handle without  resorting to changing
>> the exposure.
>
>> The histogram of values read directly from the
>> electronics will 'always' fall somewhere in between the minimum and
>> maximum values the scanner can handle.
>
> I agree, providing the system can calibrate to the current "state" of 
> the
> light source.
>
>> The 'auto-exposure' function usually takes over from there so that 
>> when
>> you look at the histogram in a preview window the x values that you 
>> see
>> are a subset of the scanners range that corresponds to the range of 
>> the
>> negative.
>
> Hum.  Typically, I believe, auto-exposure would be merely setting the
> setpoints, not varying the exposure time, but I don't know your
> scanner/software...but I just want to point out auto-exposure MAY be a
> misnomer.  Let me know what you think about that.

I agree, I thought that's what I said :(  I meant to convey that when 
you see a histogram you are usually seeing the data points spread out 
over the density range of the negative not spread out over the range of 
the scanner is capable of ( unless you are looking at a raw scan).

Not that Alex had this confused, but when I first started scanning it 
took a while to figure out why an moderately overexposed negative and a 
moderately underexposed negative seemed to fill the same space in the 
scanning software's histogram.  But then again I was bewildered when 
the same under and over exposed negatives came back from the 1 hour 
photo looking identical <sheepish grin>.


--
Kevin