Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,910   Posts: 1,556,218   Online: 969
      
Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 27
  1. #11

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Quote Originally Posted by sanking
    Donald,

    To avoid any misundersteanding the SBR/time values I gave for both the 2;2:100 and 1:1:100 dilution of Procat-HD were based on UV readings, not blue channel. That is because I am testing for kallitype and palladium printing which are sensitive primarily to UV light.

    In general I would need to substract about log 0.30 from my UV reading to approximate the blue reading. So in effect if your readings are giving you a density range of 1.6 with the blue channel reading this would be an effective DR of 1.9 or more for me with a UV reading. Did you check the results with your X-Rite 361 in UV mode?
    Sandy,

    As I have indicated my density readings were taken with an Xrite 310 densitometer (does not have a UV channel). I initially read the reflection densities of the Stouffer tablet exposures on Azo grade two and grade three. From that I was able to gain the ES of the paper. I then tested to gain an equivalent DR on my negatives by again exposing a Stouffer tablet and reading the negative densities through the blue channel.

    I had emailed you with the results of my reflection testing and you provided me with the 1.60 DR based upon my step tablet readings for Azo grade two. We had decided that probably the UV readings were not applicable when one exposes the Azo with a 300 watt reflector flood (I imagine that this source is very low in UV output). I believe that you indicated that while Azo's primary spectral response lies in near band UV it will expose to visible light in the blue spectrum. Apparently that is what occurs with the reflector floods that are widely used by Azo printers.

    I don't know of anyone that is exposing Azo with a UV source since the exposure times are generally acknowledged as being too short to be manageable. I did find yesterday that I will be able to drop back to a 150 watt reflector flood since my exposures ranged from 6 to 11 seconds with the 300 watt reflector flood lamp. I acknowledge that this is a further indication of the beneficial lack of general stain with Pyrocat developer.

    I think that the type of light source and amount of UV output may very well be the basis for the discrepency that you seem to question.

  2. #12

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    "Slightly off topic, but how do you use a step wedge in testing a negative? I have used mine for paper, but don't know to accurately expose film through it."

    The procedure I use is based on the BTZS testing system developed by Phil Davis for his Zone System workshops and described in the last several editions of his book Beyond the Zone System.

    Basically you expose five or six negatives to a step wedge, develop them, and then read and plot the film densities. Each negative gets the same exposure but a different time of development, ranging from about 1/4 to twice or three times of what would be considered normal development. I use 4X5" Stouffer step wedges for film testing.

    One of the keys to this system to the ability to accurately expose film consistently. Many people use their enlarger and timer for exposure and that works fine if you can expose accurately at about 1/10 to 1/5 of a second. Exposures longer than 0.5 seconds should be avoided because of reciprocity. However, if one really wishes to make any meaningful comparison of relative speed between films you must have a more accurate exposure system than most darkroom timers allow. For my tests I use a Metrolux light integrator/timer that provides accuracy to about 1/100 of a second.

  3. #13
    L Gebhardt's Avatar
    Join Date
    Jun 2003
    Location
    NH - Live Free or Die
    Shooter
    Large Format
    Posts
    1,708
    Blog Entries
    1
    Images
    18
    Sandy, thank you. I will look this up.

  4. #14

    Join Date
    Sep 2003
    Location
    Düsseldorf, Germany
    Shooter
    8x10 Format
    Posts
    1,021
    Images
    1
    Sandy,

    I have just developed my first Pyrocat HD 8x10 neg (PL100). As the SBR was 10 I used a dilution of 1:1:100 @ 22C, 6m30s as per your suggestion above. I do not own a densitometer so I cannot prove what I see BUT the negative looks stunning! It looks easy to print (have not printed it yet) and would probably be interpretable in both Pt/Pd and Azo.

    I developed a duplicate negative using TMAX RS 1:15 @ 22C, 13min (a recommendation by John Sexton for up to N-3) but I got zip. Maybe a bit more than zip. The negative was almost clear film. Strange that when held up to the light I could swear that I could see a very faint positive representaion of the negative. Nevertheless, there was nothing in this negative that could even come close to the detail in the Pyrocat HD negative.

    Many thanks!

  5. #15

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Francesco,

    Congratulations on your good work with this difficult lighting condition. I am very pleased that my development recommendations for FP4+ and Pyrocate-HD have proven useful to your work. Pleae let me know if you have further questions.

  6. #16

    Join Date
    Sep 2003
    Location
    Düsseldorf, Germany
    Shooter
    8x10 Format
    Posts
    1,021
    Images
    1
    Sandy,

    Thank you for those encouraging words. I do have more questions but one in particular caught my interest. Should I be looking for some kind of "stain" or "colour" on the negative? I have to admit that being a novice on pyro I cannot identify anything unusual on the negative in relation to "stain" as discussed in many threads here and elsewhere. The one thing I can say is that it looks like PYROCAT can go much further than just SBR 10 (no other non-pyro developer I have worked with could achieve more than an 8 or 9) and that what you get is very clean highlights and extreme detail in the shadows even in subjects that are far away. I have four negatives that have SBRs of 13 and I will be doing them tonight with PYROCAT (as opposed to uising my "new arrivals" of TFX-2 and Modified POTA, which I thought would serve as my back up - dont think I want to sacrifice negs on them now!).

    BTW, the film I used is Efke PL100.

  7. #17

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Francesco,

    Your comment about the look of your Pyrocat negatives, i.e. that you cannot "identify anything unusual on the negative in relation to "stain" as discussed in many threads here and elsewhere" is typical of the reaction of many persons using Pyrocat-HD for the first time. This is due to the fact that the stain produced by Pyrocat-HD is typically brown, or even brownish-black. Photographers who have previously used developers like PMK and Rollo Pyro nearly always underestimate the intensity of the Pyrocat-HD stain because by comparison with the green or greenish/yellow stain of these developers the brown Pyrocat-HD stain looks almost neutral in color. This is not the case, however, and in practice it will be found that the brown stain of a Pyrocat-HD negative will have an impact on the effective printing density of the negative that is as great, or even greater, than the green and greenish/yellow stain of other Pyro developers.

    The impact of stain is a very complicated issue and one that, from my perspective, only a handful of people really understand. I am completing at this point a rather long article on Pyrocat-HD that will go up on Ed Buffaloe's UnblinkingEye. com site soon, hopefully within the next few days. In this article I address the question of stain and its impact on varius printing processes. Look out for it as I think you will find some of my opinions on this matter interesting and useful.

  8. #18
    Jeremy's Avatar
    Join Date
    Oct 2002
    Location
    Denton, TX
    Shooter
    Multi Format
    Posts
    2,767
    Images
    56
    sandy,
    will this article include your suggested times for different films? people are always asking about times for different films and if there was one main source you could point them to it might help with a lot of confusion. I've been looking through a number of archives across the net for suggested times for HP5 (which include a range of SBR's, not just the "normal") and have found a geat deal of information but have trouble separating them into times for azo, pt/pd, or enlargement on silver, which dilution they are at, and the film speed to shoot at. I know I need to be doing my own testing, but I haven't even been able to get into the darkroom since my last postcard (quite a while ago).

    note: Francesco's question is definitely one that needed to be asked directly as it concerned more extreme SBR's than usually used.
    Let's see what I've got in the magic trash can for Mateo!

    blog
    website

  9. #19

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Jeremy,

    I will be including CI (Contrast Index) charts for all of the films that I have personally tested with either Pyrocat-HD 1:1:100 or 2:2:100. Further, there will be two kinds of charts, one based on UV reading which would be appropriate for alterenative printing with UV light, another based on Blue channel reading which would be more appropriate for AZO and graded silver papers, and with some minor adjustments, for VC papers.

  10. #20

    Join Date
    Sep 2003
    Location
    Düsseldorf, Germany
    Shooter
    8x10 Format
    Posts
    1,021
    Images
    1
    Sandy,

    I have now developed for SBRs of 11 and 13 (5m30s and 3m respectively). I still cannot believe how versatile PYROCAT HD is (and quite economical at 1:1:100 for these extreme SBRs). The negs look like they have been developed normally. In fact, I feel as if these scenes are not as extreme as I had thought when I took them. Your suggested times are spot on and I do not hesitate to recommend them using Efke PL100 8x10. A wonderful and easy combination! My next project is to try Classic 400 once I take a few more on PL100: Thank you very much once again.

Page 2 of 3 FirstFirst 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin