[Alt-photo] Digital negatives help?

Niranjan Patel nirpat89 at yahoo.com
Wed Sep 28 19:47:49 UTC 2016


OK, let me show the method behind my madness.

Please click the link and use altalt as a password to get in the page where I have added two jpegs illustrating my procedure.


After developing my initial process based on the composite black on B9180, I set out to do the colorizing negative in search of higher UV opacity needed to bump up the white point of the prints.  For that I eliminated the Blue as a variable which is probably a safe choice, so I don't have to work in the 3D.  Then I varied R and G from 0% to 100% with step size of 10% (that translates to 25-26 in RGB points) to come up an 11x11 matrix that is shown on Figure 1.  The grid lines were made with pure black (0/0/0) so the comparison of under-performance and over-performance can be visibly made. The square on the top right corner is also 0/0/0.

Figure 2 is the resulting scan of the print.  It can be immediately seen where the best cluster of squares is.  I picked the square, marked by a circle, corresponding to the 51/128/0 in the negative as the best candidate based on both the numbers as well as the fact that as one moved away from it, the squares became significantly noisier, even when the readings were comparable.  (I have noticed that the print from a colorized negative has more noise than from a straight one, particularly in the mid to darker tones for which I am working on a solution to - a subject for discussion at perhaps an another time.)

Next I took 51/128/0 as my center and created another checker board, varying R and G in smaller steps of 2% (equivalent to 5 in RGB points.)  Figure 3 is the result of that.  After printing and scanning, as seen on Figure 4, the results point to a new center of gravity for opacity which is at 61/118/0, albeit the improvement is modest - from 223 of 51/128/0 (marked by a circle) to 227 of 61/118/0 (marked by a square.)  We are really splitting hairs here, but the difference is real.  It was encouraging that although I did both of these a a few days apart, the results were consistent.  

Now about the additional black layer as per your suggestion:

You can easily test this quickly by producing a
series of digital step tablets with progressive opacities (of the black
layer) printing them all on a single sheet of OHP

You really don't have to do the step wedge, only a block of 0/0/0 (before colorizing) in order to simplify the process.  So if I take that 0/0/0 block and colorize with my old green shade of 51/128/0 and put the Black layer on Multiply and vary the opacity.  "Blending if" options at this point do not matter.  Here is what happens to the final values:

Black Layer Opacity -  Final R/G/B values

0% - 51/128/01% - 51/127/03% - 50/125/05% - 49/124/0 7% - 49/122/010% - 47/119/0

All of these values are in the matrix of Figure 3, within 2 or 3 points.  I have marked the 5% point as A and 10% point as B to illustrate.  

So are you going to start printing salt after you run out of POP? 


I have a lb of Silver Nitrate sitting in my fridge for about the same time as the POPs (hopefully it is still good) that says I ought to.  Also have some Pt/Pd chemistry that I may want to do some printing with.  May be before salt.  




 From: Don via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
 To: alt-photo-process-list at lists.altphotolist.org 
Cc: Don <donsbryant at gmail.com>
 Sent: Tuesday, September 27, 2016 5:12 PM
 Subject: Re: [Alt-photo] Digital negatives help?
4.  I use AdobeRGB 16-bit color space in Photoshop as well as in the
scanner.  Printing is done at HP's "Maximum DPI" from 1200 dpi files.    
My question was buried at the end of my long-winded backgrounder in
yesterday's post.  In any case, I think I have the answer to that one now.

I grok a lot of what you are describing, but I question your methodology. If
your blocking color is R=51, G = 128 then I would think you still have head
room to extend the UV density of your digital negative using that greenish
color path. However if you wish to use a black ink layer to target the steps
or part of the adjustment curve it should be very simple to do with the
Blend If method I listed for Henry. 

IME, doing that makes the negative get very dense quickly. At the time I was
testing this method, I was producing VDB and kalitype negatives and found
that the opacity of the black only layer needed to be set to a very low
amount - like about 5%. You can easily test this quickly by producing a
series of digital step tablets with progressive opacities (of the black
layer) printing them all on a single sheet of OHP. I flatten all of the
layers before printing and use the Text tool to label each giving me a
record to keep in my testing files. That way you can hone the required value
with one or two sheets of paper. For those two processes a black ink really
isn't needed when printing with Epson OEM pigmented inks. 

So are you going to start printing salt after you run out of POP? 

Don Bryant


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