Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,545   Posts: 1,544,444   Online: 1015
      
Page 1 of 3 123 LastLast
Results 1 to 10 of 22
  1. #1
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,022
    Images
    65

    Latest work on emulsions

    Here is a sample of a glass plate made at a recent workshop.

    It is Orthochromatic and has an ISO of 40 - 60. It was exposed at 1/100th f8.

    The process was 9 minutes in D76, stop, fix in Kodak RLF + hardener.

    The image represents an area of about 3x4 inches of the entire 4x5 plate due to edge defects and frilling. The edge of one such defect can be seen at the upper right of this picture.

    There appears to be less flare than would be expected due to the absence of an absorber dye or AH layer.

    This is an SRAD (Single Run Ammonia Digest) with Erythrosine used as the green sensitizing dye. It was made using Phthalated Gelatin (PA) and was ISO washed with an acid base cycle. It was chemically sensitized with sulfur using Sodium Thiosulfate. If I were to use gold, the speed would be about one stop faster, as a guess OTOMH.

    The Dmin was clean, and the contrast was good. This plate was coated at about 500 - 700 mg/foot sqare of silver with about 1000 mg of gelatin including the PA gelatin. Coating was carried out with a plate coating doctor blade. This plate was kept for 4 days to complete the hardening cycle as far as possible. I have 2 more plates awaiting testing.

    In addition, there were coatings on Estar support at 5 mil (about 300 mg / ft square of silver and about 750 mg of gelatin / ft square. Paper coatings were also made and had the expected speed of about 100 - 200 ISO due to back reflection. These paper coatings made nice paper negatives.

    PE
    Attached Thumbnails Attached Thumbnails Detail of glass plate at ISO 40.jpg  

  2. #2
    johnnywalker's Avatar
    Join Date
    Sep 2002
    Location
    British Columbia, Canada
    Shooter
    Multi Format
    Posts
    2,255
    Images
    78
    I won't pretend to understand the process that led up to this picture, but it seems to have been successful! Congratulations. I'm glad to know that someone is doing this.
    If I had been present at the creation, I would have given some useful hints for the better arrangement of the Universe.
    Alfonso the Wise, 1221-1284

  3. #3
    Neanderman's Avatar
    Join Date
    Mar 2004
    Location
    Ohio River Valley
    Shooter
    Large Format
    Posts
    575
    Quote Originally Posted by Photo Engineer View Post
    Here is a sample of a glass plate made at a recent workshop.
    Very nice! I wait with bated breath for anything else you are willing to share about this.

    Ed

  4. #4
    Jadedoto's Avatar
    Join Date
    May 2006
    Location
    Lexington KY
    Shooter
    Medium Format
    Posts
    147
    Images
    3
    Wow! If only I could get my emulsions to look like that- har! I'm very impressed!
    Vincent Purcell
    Lexington KY Photographer + Media Artist
    http://vincenttpurcell.com

  5. #5
    htmlguru4242's Avatar
    Join Date
    Aug 2005
    Location
    Sandy Hook, CT
    Shooter
    Multi Format
    Posts
    973
    As usual, PE, very nice job!

    Any details on the emulsion?

  6. #6
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,284
    Images
    20
    Very nice tonal scale, Ron. The mechanical coating issues can be worked out, I'm sure. That looks like a very viable plate emulsion.

    Out of curiosity, it looks like there's a moire pattern over the Macbeth chart. Is that just a scanning artifact or is that a coating issue (that looks like a scanning artifact)?
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  7. #7
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,022
    Images
    65
    David;

    Thanks.

    I was perplexed by the pattern. It is not on the plate, but I cannot eliminate it during scanning. It appears only on that plate. I have 3 here and that is the best, but it has that pattern when scanned.

    The others have reticulation and other defects. This one was held for 4 days before processing and that reduced frilling and reticulation. So, that appears to be a problem inherent in the workshops that I have been facing. We have to process within 24 hours to meet the timetable, but the plate and film coatings cannot harden fast enough. This time, I had 4 plates left over.

    This was a scan of the plate. I would think that a print would require a grade 3 paper and slight overexposure to achieve a good print. I'll probably be doing that soon.

    PE

  8. #8
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,022
    Images
    65
    David;

    An afterthought. The scan was at 600 dpi, and I had to reduce it to a lower value to allow the upload. I wonder if the resizing caused the problem?

    PE

  9. #9
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,022
    Images
    65
    I checked the original scans. I made 3 of them. If I scanned as a positive, and then inverted the image, the artifact is not there, but if I scanned as a negative (to get a direct positive) the artifact is there.

    It seems to be unrelated to resizing.

    I'm stumped.

    PE

  10. #10

    Join Date
    Sep 2006
    Location
    OH
    Shooter
    35mm
    Posts
    1,789
    Images
    2
    Looks like a scanning artifact. What is it called, newton rings?

Page 1 of 3 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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