[alt-photo] Re: Multi-Neg Printing Methods

[etienne garbaux]

Francesco wrote:

>I'm doing a bit more research into multiple negative printing.
>
>I've been looking quite intently into some of the techniques used by Irving
>Penn and recently its been recommended that I look into the printing of
>Salto in Belgium. The key element that I'm interest in is the use of
>multiple negatives for printing highlight, mid-tones, and shadows. Penn made
>multiple negatives in the darkroom and printed them in register and was able
>to achieve his unbelievable platinum prints

If there is a problem with Pt (at least the traditional process), it 
is that prints often lack contrast in the midrange and shadows, and 
lack density in the darkest shadows.  One can express this by saying 
that the perfect camera film for Pt would have an "all shoulder" 
characteristic curve and be capable of very high Dmax (up to 
~4.0).  This is the opposite of, say, Tri-X Pro, which has an 
"all-toe" characteristic.  (For best Pt prints, even with 
"straight-line" films you need to get the shadows well up off the 
toe.)  The only direct way to approximate this in one negative in the 
wet darkroom is to overexpose and overdevelop the negative, then 
attack it with a super-proportional reducer.  However, the films 
available today do not have enough density headroom to do this, 
particularly when you expose to get the shadows up off the toe.  Even 
with the films available in the '60s, the resulting curve was not 
really ideal.  (There used to be an indirect way to make ideal Pt 
negatives -- the Kodak Dye Transfer process was very flexible with 
respect to tonal mapping, and you could make excellent monochrome Pt 
negatives on Dye Transfer transparency material, adjusting the 
contrast and density separately in the highlights, mids, and 
shadows.  But it was a LOT of work -- though not as much as multiple 
negatives, IMO -- and the materials are no longer available.)

Multiple negatives help by (i) allowing you to "build" a piecewise 
approximation to a contrast correction curve in a wet darkroom, (ii) 
effectively extending the DR of your negative, if the original 
negative has insufficient DR to fill the ES of your Pt process (note 
that many camera films today cannot reach a sufficient Dmax to cover 
the ES of Pt); and (iii) allowing you to add a second 
coating/exposure for increased Dmax, if you want to try that.

Digital negative processes should obviate (i) and (ii), so if you use 
diginegs, you should only need multiple negatives if you decide to 
try multi-coating.  Of course, this brings in all the problems of 
maintaining registration with a wet step in the middle of the 
process, and the ultimate extension of Dmax is not as dramatic as 
you'd think it should be, in any case.

Re: exposure -- If you use more than one negative, the areas of the 
"shadow" negative that represent mid-tones and highlights are 
essentially all blocked at or near the film Dmax, so they add very 
little to the midrange and highlight exposure.  The entire DR of the 
shadow negative is devoted to the shadow regions of the image, to add 
contrast there.  If you use three negs, the midrange negative is 
blocked in the highlights (so it doesn't add much to the highlight 
exposure) and you hope that the cumulative shadow exposure from the 
highlight and midrange negatives is swamped by the shadow negative 
exposure (but this is not always the case).

Best regards,

etienne