RECIPROCITY BLACK & WHITE FILM

Discussion in 'Exposure Discussion' started by hortense, May 24, 2006.

  1. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    It appears Digital Truth has posted incorrect reciprocity data according to my experience with exposures less than 15-minutes. Have NOT tested Ilford for reciprocity but used their formula meter reading ^ 1.49.

    BLACK & WHITE FILM
    Digital Truth for ALL B/W film (http://www.digitaltruth.com/techdata/reciprocity.php)
    1 sec reading: expose 2 sec and N-10%
    10 sec reading: expose 1 min and N-20%
    100 sec reading: expose 20 min and N-30%
    Kodak for 320TXP
    1 sec reading: expose 1 sec and N-0%
    10 sec reading: expose ≈18 sec and N-1
    100 sec reading: expose ≈4-min and N-1 1/2
    Ilford
    1 sec reading: expose 1 sec and N-0%
    10 sec reading: expose 30 sec and N-10%
    100 sec reading: expose ≈15 min ^1.49=15 min ≈N-30%
     
  2. colrehogan

    colrehogan Member

    Messages:
    2,016
    Joined:
    May 11, 2004
    Location:
    St. Louis, M
    Shooter:
    Large Format Pan
    I would just download the tech sheets for each film you are using or plan to use and they include reciprocity information.
     
  3. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    Kodak 320TXP and Ilford reciprocity data are documented by each company. More specifically Ilford states that there film reciprocities are based on Uncorrected Time or Meter Reading seconds ^1.49. However, if you have some information that would substantiate or correct what Digital Truth has claimed it would be helpfut to forum viewers. Perhaps other viewing this verify?
     
  4. RalphLambrecht

    RalphLambrecht Subscriber

    Messages:
    8,296
    Joined:
    Sep 19, 2003
    Location:
    Florida
    Shooter:
    Multi Format
    My co-author conducted a reciprocity test lately, but the data is not evaluated yet. So I can't post anything right now. Nevertheless, I have a working reciprocity chart for Kodak films and it matches the above table closely.

    One factor needs to be considered. What is the color temperature of the low-light condition, which is causing the reciprocity failure? Film has a very different sensitivity to blue, green or red light. If we are facing a tungsten low-light condition, the reciprocity chart made with dim daylight data will give false results.

    Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.
     
  5. Roger Hicks

    Roger Hicks Member

    Messages:
    4,913
    Joined:
    May 17, 2006
    Location:
    Northern Aqu
    Shooter:
    35mm RF
    Dear Ralph,

    Oh dear! Giving away trade secrets!

    Couldn't agree more!

    Cheers,

    Roger
     
  6. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    Thanks Ralph. I did not realize this factor was involved. I thought that the increased exposure requirements took this into consideration - but, you tested - that settles it. Sounds like you and a coleague are doing some in depth reciprocity testing. I would be nice to do better than a very broad estimate. Keep us informed as you get more data?
     
  7. Digitaltruth

    Digitaltruth Advertiser Advertiser

    Messages:
    77
    Joined:
    Dec 9, 2005
    Shooter:
    35mm
    Hi Hortense,

    The data on our site comes from many reliable sources, but there can always be errors or inconsistencies. The reciprocity data is a guideline only and testing needs to be done with individual films.

    We are happy to accept any improvements to our site, and will credit all contributions, so if anyone can supply better data, then please send it to me and we will make it available on our information pages.

    --Jon
     
  8. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    Jon - You site is fine. Pardon my comments - not intended to throw spears. We value the service your site provides. I was hoping others would chime in with the reciprocity data they have used successfully.
     
  9. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    Jon - Here is what I have successfully used for TriX. Ilford calculations are
    Meter Readiing in seconds ^1.48.
     
  10. hortense

    hortense Member

    Messages:
    612
    Joined:
    Jun 17, 2004
    Location:
    Riverside, C
    Shooter:
    Large Format
    320TPX

    Here it is.
     
    Last edited by a moderator: Sep 19, 2006
  11. Digitaltruth

    Digitaltruth Advertiser Advertiser

    Messages:
    77
    Joined:
    Dec 9, 2005
    Shooter:
    35mm
    Thanks.