Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,491   Posts: 1,542,946   Online: 895
      
Page 2 of 2 FirstFirst 12
Results 11 to 20 of 20
  1. #11

    Join Date
    Oct 2006
    Location
    Van Buren, Arkansas
    Shooter
    Large Format
    Posts
    2,412
    Images
    101
    It was the E-2 and E3 processes that required reversal exposure to light. The E4 process had chemical reversal, as does E6. The reversal bath does this just prior to the color developer step. It is not critical at all. It does it every time. Only the first developer, first wash and first minute of the reversal bath step are done in the dark (if you use dip and dunk sink-line style processing), all the rest of the steps can be done in full room light. So about 10 minutes in the dark and you can switch the lights on. Of course if you process in a daylight tank, all the steps are done in room light after you load the film in the tank. I have been processing E6 since Kodak introduced it. It is easy, economical and quite within the reach of the average home darkroom enthusiast. Don't be discouraged. Only the first developer requires precise temperature control, and it is only for 6-6.5 minutes. The rest of the chemicals can drift a bit and you can still get spectacular results. The E-6 Kodak chemistry is all liquid concentrates, it mixes easily with no effort into working solutions and works with most, if not all municipal water, no special distilled water needed.

  2. #12
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,005
    Images
    65
    Since the introduction of E4 and E6, either flashing or chemical reversal could be used at the users discretion. In E4, the chemical used was t-butyl amine borane, which was quite nasty. In E6 the chemical used is Stannous Chloride which is much milder, but subject to deterioration in solution.

    Today, plastic reels are made with one transparent side so that you can flash with light evenly. Many are made with two transparent reels. Old reels were black and caused more problems with E6.

    Kodachrome uses a mixture of flashing and chemical reversal. They use a Red and Blue flash and then a chemical reversal for the final development (Magenta).

    All reversal processes suffer from variability due to the high pH of the color developer(s) used which usually run about pH 11 or higher. This high pH value is not stable and as the pH drifts down, the developer deteriorates. This is NOT true of the RA and C41 processes which use a much lower pH developer which is buffered optimally.

    PE
    Last edited by Photo Engineer; 03-21-2008 at 10:01 AM. Click to view previous post history. Reason: Fixed error

  3. #13

    Join Date
    Oct 2005
    Location
    SE London.
    Shooter
    Large Format
    Posts
    585
    Images
    22
    PE,
    how to black reels cause problems with E6?

  4. #14
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,005
    Images
    65
    If you use re-exposure by light, the opaque black reels would allow insufficient light to penetrate to the center of the film. At that time (E1, E2 and E3), Kodak suggested removing the wet film from the black reel and reexposing to light. This was to be done underwater to facilitate removal and rethreading of the film. (Can you imagine that? It was a chore I avoided.)

    Anyhow, the reel designers changed to either all transparent reels or at least reels with one transparent and one black side.

    PE

  5. #15

    Join Date
    Aug 2007
    Shooter
    Med. Format Pan
    Posts
    132

    Kodachrome re-exposures

    David, Kodachrome requires two (red and blue light) reexposures; one through the emulsion and the other through the base, not three re-exposures.

    Quote Originally Posted by David A. Goldfarb View Post
    In reversal processing that involves exposure to light, my impression is that the film is usually fogged completely, so that as long as a certain minimum exposure is achieved, the time isn't critical. For Kodachrome there are three different exposures, so I'm sure it's more complicated.

  6. #16
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,274
    Images
    20
    Quote Originally Posted by Discpad View Post
    David, Kodachrome requires two (red and blue light) reexposures; one through the emulsion and the other through the base, not three re-exposures.
    Thanks, that makes more sense. I was puzzling for a moment at how they might do three.
    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. #17
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,005
    Images
    65
    Ummm, I think I explained that in post #12 above.

    PE

  8. #18

    Join Date
    Oct 2005
    Location
    SE London.
    Shooter
    Large Format
    Posts
    585
    Images
    22
    Quote Originally Posted by Photo Engineer View Post
    If you use re-exposure by light, the opaque black reels would allow insufficient light to penetrate to the center of the film. At that time (E1, E2 and E3), Kodak suggested removing the wet film from the black reel and reexposing to light. This was to be done underwater to facilitate removal and rethreading of the film. (Can you imagine that? It was a chore I avoided.)

    Anyhow, the reel designers changed to either all transparent reels or at least reels with one transparent and one black side.

    PE
    Ah, so at some point E6 didn't use a chemical for the reversal step, but it was done by exposing the film. Sounds like a nightmare!

  9. #19
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,005
    Images
    65
    You misunderstood or my explanation was not clear.

    E4 and E6 used chemical or light reversal. The chemical reversal was invented due to problems with light reversal in E1, E2 and E3. The problem was partially solved by 2nd party transparent and half transparent reels sometime in the 70s or thereabouts. Maybe even earlier.

    PE

  10. #20

    Join Date
    Oct 2005
    Location
    SE London.
    Shooter
    Large Format
    Posts
    585
    Images
    22
    I understand. Thanks for taking the time to explain.

Page 2 of 2 FirstFirst 12


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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