Re: Digital Carbon Negatives

RE: Digital Carbon NegativesThank you, Sandy- love the large print- I can
 almost see it but for the astigmatism... Susan
  ----- Original Message -----
  From: Sandy King
  To: alt-photo-process-l@sask.usask.ca
  Sent: Sunday, March 07, 2004 4:58 PM
  Subject: RE: Digital Carbon Negatives

  For some reason I did not receive some of the messages alluded to in this exchange, but to the extent that I can follow the topic here are some observations.

  I have not compared digital negatives of the type made by Keith (pyro-color) with regular pyro negatives. I use digital negatives for making carbon prints but they are not spectral negatives. However, based on my understanding of how digital negatives print in general, with kallitype and palladium as well as carbon, I can speculate with some degree of confidence that a digital negative would print much faster than a regular in-camera negative developed in a Pyro developer because it would have much lower B+F and much lower density in the shadows. Typically my digital negatives print in carbon with both the NuArc 26-1K and a bank of BLB tubes in about 100-160 units, where one unit equals one second. In-camera negatives take much longer.

  Which brings me to the second issue. Current generation Pyro developers produce proportional stain, very little where silver densities are low, much more where silver densities are high. Since the stain blocks UV light the result is that Pyro stained negatives print with more contrast than is apparent to the eye. In theory a correctly exposed and developed Pyro negative will not take any longer to print than a negative correctly exposed and developed in a traditional non-staining developer. In practice that is usually not the case, for two reasons.

  1. Most people give more exposure than is necessary and this extra density drives up B+F and Zone 1 and 2 values more for a Pyro stained negative than for a traditional one. For example, an increase of one extra stop in exposure will typically result in an increase in B+F value with traditional negatives of about log 0.15, or about 1/2 stop, but double or even triple this for a Pyro negative. In other words, if you over-expose the negative by one stop your printing times with Pyro negatives will increase by between 100-150%.

  2. Many people are using films that are less than ideal for alternative printing because they have such a high rise in B+F from the longer development times we must give them to get enough contrast. Films like BPF and HP5+ are good examples. And of course, as I noted above, an increase of 0.15 for a traditional negatives becomes an effective increase of 0.30 to 0.45 for a stained negative.

  What to do?

  1. Don't overexpose. With the long development times needed to reach the CI necessary for alternative printing most films should be rated at full emulsion speed, or even higher. A very common mistake is to reduce the EFS of the film thinking that this will give the density necessary for alternative printing. But it is more contrast you need, not more density.

  2. Reserve films like BPF and HP5+ for medium and high contrast scenes.

  3, Films that work well in low contrast lighting are FP4+, Tmax 400, Delta 100.

  4. If you must shoot films like BPF and HP5+ in very flat lighting I would recommend that you either develop the film in a Pyro developer that does not produce a lot of stain, ABC Pyro at the 1:1:1:7 dilution for example, or use a very high energy developer like Kodak D19, which you will have to mix from scratch.

  Sandy King

    Hi Michael,

       I am planning on doing carbon prints from both digital and pyro
    developed
       negatives this fall. I am wondering if anyone has done side-by-side
       comparisons to the pyro color-balance formula Keith is using, and an
       actual
       pyro stained neg.

       Just curious.

       Did we meet at APIS?

       :)

    No Michael, I don't think that we did meet, I was very low key this year
    and not very out going that week since I was still grieving over the
    loss of my Norwegian Wood cat in May. :(

    When you use the phrase pyro generically I'm not clear what developer
    you are using. Assuming that your 'pyro' negs have the proper contrast
    index then they should work fine for carbon. If you mean PMK pyro than I
    would recommend not using it at all for any process used with UV
    printing, since the B+F levels required for proper contrast levels
    usually gets excessive.
    And PMK stain is too effective at blocking UV light causing
    extraordinarily long print times. According to Sandy King, PMK developed
    film to the proper contrast for carbon have very high levels of B+F.

    I know Sandy King has been quite successful making carbon prints using
    digital negatives produced by an inkjet printer. If you have not tried
    making alternative prints using inkjet negatives then you are in store
    for quite a surprise as they can print very fast. Contrast control is
    achieved through adjustment to the digi neg contrast rather than
    introducing a contrast agent of one sort or another.

    Specifically in the case of carbon printing with film based negatives
    contrast can be controlled by adjusting the dichromate concentration or
    as some printers do, by changing the proportion of gelatin to pigment
    percentage. If you are purchasing your carbon tissue the latter method
    of course isn't possible, so using a digi neg made be more desirable.
    Carbon prints made from digi negs look very nice but they don't have
    quite the presence of a print made from an original in camera negative,
    although most viewers will never notice.

    Perhaps our carbon experts can provide much more detailed information
    and correct any mistakes I've made in my reply.

    Best,

    Don Bryant
Received on Sun Mar 7 21:26:37 2004