Good Grief: (was Re: another 3 layer gum attempt
On Tue, 21 Jul 2009, Paul Viapiano wrote:
I have a Stouffer 21-step tablet, and I understand how you can evaluate the emulsion from it, but how will that translate when making your digital negative without a densitometer? Shouldn't I use a (uncurved) step-tablet generated from my printer to find my exposure time?Good grief, if I had to understand, let alone follow, all the fine points "explained" in this thread, I doubt I'd have made ONE gum print, at least not without serious brain damage, nor would I have dared demand it of our "space-cadet" undergraduates (who did some exquisite gums) for 15 years.
We do see however, how the process has gotten a bad rap -- for being difficult, tetchy, uncontrollable, arcane, mysterioso, etc. Could we please remember that early gum printers (as witnessed by the "Truth/
Beauty" book and show) made exquisite gum prints, many of them exquisitely "realistic" with none of our current folderol? More than 100 years ago -- without, as I calculate, the benefit of any electricity at all.
But before I make what could be a couple of helpful suggestions, I have a comment/question: "Cadmium yellow" was mentioned. I don't have the data on that particular brand, but AFAIK cadmium in actual paint has been outlawed as being as deadly as lead in the water and land. Of course the name may mean "cadmium hue" or like that, but in any event "cadmium" is possibly the most opaque paint in the palette, so hardly suitable for tricolor printing -- unless as color #1, which IME leads to register problems, besides not solving the problems mentioned.
As for "evaluating the emulsion" and making a digital negative without a densitometer, as desired by Paul, there's a dandy NOT digital (if you could believe) but plain old analog method, simple as ABC. Go to alternativephotography.com (there's a more detailed address which I've lost, but it's in the "book" section of Malin Fabbri's website). The method is llustrated on page 38 of Post-Factory #1 which is there in its entirety (and can be downloaded as PDF for free if it pleases you).
This section, titled, "The Ordered Negative" shows how to "read film density with two small white cards and a transmission guide, using your lightbox instead of a densitometer." Page 38 illustrates the act (because I had room to put it there) but the actual instructions "for measuring film density" appear in a mere 3 paragraphs, page 41.
You do however have to have a Stouffer step tablet, which is, in case I haven't mentioned it, a magical tool of a thousand uses... tho 6 or 8 or 10 is better than one -- you can test all your variables with one exposure. (Though someone reading this may know whether you can mimic a 21-step digitally.) No, I did not invent this method, tho I've taught it & taught it -- and I DO, by the way, also have a densitometer. I sometimes use it as an after-the-fact check, but ... does a densitometer tell you about grain? about stain? about tone?
Finally, I mention that amother beauty of gum is the infinite variables you can summon by development alone: length of soak, temperature of soak, agitation (or not) of soak, addition of ammonia to the water, brushing, spraying, etc. etc. & that's not to mention variations by texture & sizing of the paper, among others.
(But, AFAIK, ixnay on actual *cadmium* in paint !)