Dry Plate Photography

Characteristic Curve Control - Different Lights

 
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Since the beginnings of photography, rendition of color and brightnesses have been conventionalized by the limitations of the negative material.  In the early days, with the color-blind plates sensitive only to blue light, we became accustomed to white skies, dark lips, and very dark foliage.  Later, with orthochromatic emulsions, responding to all parts of the spectrum except deep orange and red, foliage could be rendered more faithfully, but skies were still light and blank, lips still dark, and the rendition of clouds in landscape was considered a great feat.  But with the appearance of the panchromatic emulsions, responding to the entire visible spectrum, we grew accustomed to dark skies (exaggerated by the use of filters), light lips, and many other representations that have become as "conventional" as those of earlier times.

The modern photographer, however, has such a wide choice of negative materials, together with filters to modify their effects, that he need be bound by no conventions of expression.  After learning — through experience plus logical experimentation — the differences between emulsion types, and the effects of various filters on tonal values and contrast, he has available a stimulating gamut of interpretive possibilities.'

Ansel Adams, The Negative, 1948, pp 4-5. 


All Light Is Not Equal

I don't know if Ansel foresaw the disappearance of 'a wide choice of negative materials', at least in 1948, but what he said then can hold true for us today — if we take matters into our own hands.  Learning a few lab skills is the least of it.  The challenge is learning to unlearn 'panchromatic visualization' and process-by-quantification.

The first idea to rethink is 'speed'.  Beyond a general expectation that one recipe is usually faster/contrasty'er/grainy'er than another, each handmade batch of emulsion will be a little different from another, even if the recipe is identical.  The infinity of chemical and physical reactions involved with emulsion making is the reason Kodak, et al, obsessed about control.  Their obsession (if not their secrecy) was justified.  They were commercial operations, selling to a public that they, in turn, were teaching to demand consistency.  In very short order, the public had been taught that photographic materials came from factories. 

The effective speed of a plate will be affected not just by the emulsion-making steps, but by your choice of developer, by the time of day (i.e. color temperature), filter factors, and where on the characteristic curve of the emulsion you looking and what exposure/development time combination you choose to maximize the quality of plate.  I highly recommend reading The Negative, 1948 edition.  No one has ever said it better than Mr. Adams.  Some people read A Christmas Carol once a year.  I read The Negative.

Second, treat each new batch of plates as a fresh, unknown set of qualities.  I always coat four 4"x5" plates per batch, no matter what size plates I'm coating otherwise.  For each of my camera/holder sizes I have one holder retrofit with a 4"x5" adapter. (There's more about those in the 'Tools' section.)  Before I take the big plates out in the field, I test the 4"x5"s in my backyard to get a sense of the emulsion.  I keep a couple of developers mixed up (Defender 55dwr and Kodak D-19, plus PMK Pyro if bright sun is expected — a rarity here) to test the plates.   After I know how the emulsion will behave, I can expose and develop the rest of the plates accordingly.

Below, I begin the first of my own explorations into the nature and control of non-panchromatic emulsions.  I start with color temperature, because it is the easiest thing to overlook.  To a color-blind emulsion, all light is not created equal.   I follow this with the first of my work with filters.  In addition to these factors, I hope to start looking into some simple color sensitizing additives someday soon.


 

 Effect of Color Temperature

Color changes throughout the day and throughout the year.  The warm light of early morning and late afternoon is especially sought after by color landscape photographers (at least those who don't rely on filters or Photoshop).  With non-panchromatic emulsions, there's more going on.  All light isn't equal.

This plate was exposed late in the day.  The sun was still bright, but it was a warm, reddish light.  Because color-blind emulsion isn't sensitive to that part of the spectrum, there was, in effect, much less light available to the emulsion.  I exposed the plate for 10 seconds at f/22 and developed in PMK pyro for 15 minutes.



An interesting quirk of color-blind emulsions: The exposure of the yellow lilies is much more 'natural' than when the exposure was at mid-day.  They print out light gray rather than black, as they would if the plate had been exposed at mid-day under high UV light conditions.   Note, though, the halation around the petals in the enlarged crop.

On the left: A digital print from a flatbed scan of the plate.  Photoshop tools are limited to curves, burn, and dodge (plus an unsharp mask to correct the resolution). Below: an enlarged crop of the yellow lilies.

On the left, with a crop below: A digital print from the plate photographed on a light table.  The halation obvious in the flatbed-scan is not visible here.


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