Re: [Leica] OT: Digital Zone System

[Douglas Herr <telyt@earthlink.net>]

Martin Howard <mvhoward@mac.com> wrote:

> I've decided to learn (properly!) the craft of photography.  
> I'm starting with exposure and development: I've done these 
> before, so this isn't totally new ground to me.
>
> I find that thinking in the Zone System is a useful tool.  I > think of zones in terms of tonality in the print, rather than 
> in terms of densitometry, in terms of placing a chosen scene 
> luminance in a zone, seeing where the other luminances fall, 
> and I get the principles of expanded and contracted 
> development to fit the contrast range of the scene to the 
> contrast range of the negative.
>
> However, and this is where the monkey wrench gets thrown into 
> my thinking process, I work (unfortunately) with a digital 
> darkroom these days.  While I can perfectly understand how to 
> calibrate my printing process so that I get Zone 0 to Zone X 
> in the print, the scanning process is throwing me off.
>
> I use a negative scanner in which I can set exposure manually 
> or automatically.  What I would like to do is ensure that I 
> develop my film such that I'm certain that the scanner will 
> be able to scan all the tones correctly.  But I'm not sure 
> how to go about doing this.  If I scan clear film (base+fog) 
> then all I get is a frame of noise, not a frame of a single 
> colour.  If I were to shoot a scene with a Kodak grey card in 
> it, then I don't know how to ensure that it will scan as Zone 
> V each and every time, since the scanner (even on manual 
> exposure) seems to compensate how it maps the digital levels 
> 0 -- 65,535 to the negative density differently depending 
> upon the distribution of those densities in the negative.
>
> Am I missing the point here?  I would like the scanner to 
> capture the widest possible range of densities (within the 
> capabilities of the scanner), and to be absolutely certain 
> that it will do this regardless of the range of density in 
> the negative.
>
> If it matters, I'm using a Minolta Dual Scan III and the 
> Photoshop plug-in for this scanner, although I'd like to 
> understand the general principles at work here.


Martin, how do your histograms look?  Is there any clipping at either the high or low end of the tonal scale?  If not then you have captured the entire tonal range of your negative.  If your blacks are not black enough or whites are not white enough or your middle gray isn't the right tone you can adjust these with a Levels adjustment layer.  Mapping the captured tonal range to the desired tonal output comes next, and can be done with a Curves adjustment layer.  I recommend adjustment layers instead of adjusting the original image data so that your adjustments can be modified if desired without losing tonal gradation.  Too many adjustments to the original data will give your histogram a 'saw-tooth' look, meaning that you've lost some tonal gradation.


Doug Herr
Birdman of Sacramento
http://www.wildlightphoto.com
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