Switch to English Language Passer en langue franÁaise Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,947   Posts: 1,557,852   Online: 789
      
Page 4 of 6 FirstFirst 123456 LastLast
Results 31 to 40 of 52

Thread: latensification

  1. #31
    Nicole's Avatar
    Join Date
    Sep 2004
    Shooter
    Multi Format
    Posts
    2,548
    Images
    8
    Claire, I got lost somewhere between erborate and perborate...
    I'm with you Cheryl.
    Geeesh!
    Helen, can I pass as a semi-perborate blonde? :P

  2. #32

    Join Date
    Dec 2004
    Location
    Milwaukee, Wi
    Shooter
    35mm
    Posts
    3,242

    I should keep my opinion to myself but

    I should keep my opinion to myself...I know you did not ask me but I feel so strongly that you are so much more to be likened to a Lotus than to say a Mack, SAAB or Peterbilt Nicole. Just passing remark in the righthand lane.

  3. #33
    Bob Carnie's Avatar
    Join Date
    Apr 2004
    Location
    Toronto-Ontario
    Shooter
    Med. Format RF
    Posts
    4,676
    Images
    14
    Claire

    Just so you know ,I am still watching this thread as it contains some really interesting and valuable stuff that I think I can use towards this night project that I am about to start. Usually I shoot a few hundred rolls before I even get a feel for a project. If any of the suggestions posted here help me it will save me hundreds of $$$ as well as improve the imagery I want to produce. What I like is the level of competence some of the posts put forth to this discussion. very good thread.

  4. #34
    Reinhold's Avatar
    Join Date
    Aug 2003
    Location
    Washougal, Washington
    Shooter
    Multi Format
    Posts
    687
    Images
    14
    Thought you might like a peek at my set-up for low level light latensification.

    On the far wall of my darkroom, I have a piece of peg-board with a row of hooks spaced for 6 rolls of 120/220 film. I use 12 common paper clamps, the 6 upper clamps and the 6 hook ends are dabbed with glow paint. The 6 lower clamps have 6 ounce fishing weights attached to keep the film from curling and swinging around.

    When I'm latensifying 8x20 film, I peg in some extra hooks (which have a dab of glow paint on the ends) at the appropriate places on the peg-board. To locate the clamp on the film end without biting into the emulsion, I made a simple jig out of mat board (again, with glow paint at the appropriate places) that guides the clamp to the middle of the film end and limits it to a 1/8 inch "bite".

    At the opposite end of the darkroom, 11 feet away, I put a common Kodak 5-1/2 inch safelight with a #3 filter and a 7.5 watt bulb. A variety of "waterhouse stops" limit the light output according to film speed. The one to the side has a few strips of tape to "adjust" the light output. I haven't got around to making a proper one yet, it's been working ok for the past 5 years....

    I've adjusted the light output "stops" for a consistent 16 minute latensification period for all of the films that I use. My darkroom is in the basement. During the day I darken the outer rooms so I can get in and out while the film is being latensified.

    That's how I do it...
    Attached Thumbnails Attached Thumbnails Latensify wall.jpg   Latensifier lamp.jpg  

  5. #35
    Nicole's Avatar
    Join Date
    Sep 2004
    Shooter
    Multi Format
    Posts
    2,548
    Images
    8
    Claire, thank you... (blushing)

    Quote Originally Posted by Claire Senft
    I should keep my opinion to myself...I know you did not ask me but I feel so strongly that you are so much more to be likened to a Lotus than to say a Mack, SAAB or Peterbilt Nicole. Just passing remark in the righthand lane.

  6. #36
    Helen B's Avatar
    Join Date
    Jul 2004
    Location
    Hell's Kitchen, New York, USA
    Shooter
    Multi Format
    Posts
    1,557
    Images
    27
    Once again, thanks to Claire for bringing this to our attention.

    So, post-exposure latensification by low intensity light appears to produce better results than chemical latensification while permitting normal film development, possibly by a commercial lab. The drawback is the slight problem of doing the post-exposure itself if you donít have a darkroom. To date I have made my tests with in-camera latensification. This allows different amounts of latensification on each frame, but it is extremely time-consuming, especially as very long ultra-low intensity exposures seem to lead to less fog than shorter ones at a higher intensity. The Ďbetterí the reciprocity characteristics of the film, the more important this may be (I still have a lot of tests to do to satisfy myself that this is true). Iím also looking at the timing of the latensification exposure: how much do delays affect the result?

    Patrickís circular affair with a central light didnít appeal to me, so I thought of another obvious way of doing it: take some square section drainpipe or other long box affair, arrange a simple film holder inside, make a long slot in the other side and cover it with a dense light attenuator made from layers of exposed, developed silver-image film. Itís designed for use without a darkroom, and to be as compact as possible.

    Here are the rough details of the contraption Iíve started to work on.

    The film is wound into the box on an endless belt of polyester film. The film leader is attached to the belt by a film clip that allows any misalignment to be accommodated. The tail end of the film is simply taped to the belt. A modified changing bag will cover the loading end of the box. The end of the box has an additional cover to use when the changing bag is open. The exposure itself is made in dim room light Ė possibly measured with a lightmeter.

    I decided on the endless belt idea to prevent scratching of the film and to permit winding to be done from the loading end Ė inside the changing bag. If the box was big enough, and the belt wide enough, it could be used with sheet film. I've tested the film loading idea with a steel tape measure instead of a belt - this works well enough with 35 mm and is very simple, though a little awkward. A short 'axle' keeps the front end of the tape under control.

    Best,
    Helen

  7. #37
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845
    Quote Originally Posted by jdef
    Should I be worried that a pinhole might not provide even enough light over the surface of the film? Perhaps a group of pinholes?
    Seems to me the pinhole will project a pinhole image of the light source on to the film. That would be bad...

    Solution: use a diffuser between light source and pinhole, evenly illuminated by the light source (you can check with a light meter, with the filter removed from the safelight), large enough that the image of the diffuser will cover the entire film. Build this all into a black foam core box and you have a latensification unit that could potentially be operated (including inserting and removing film holders) in a lit room. There'll be some light lost to scattering by the diffuser, so you may need to experiment with light levels and exposure times, but that and getting a good light seal ought to be the only significant issues.

    Of course, a group of pinholes would be better in terms of passing more light (assuming you're using a very dim source -- one advantage of a small, single pinhole is that you don't *need* a very dim source), as long as the diffuser is large enough so that every pinhole's image of the diffuser covers the entire film.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  8. #38

    Join Date
    Sep 2002
    Location
    Willamette Valley, Oregon
    Shooter
    Medium Format
    Posts
    3,684
    IF a pre or post 0.1 exposure is given and that much attendent fog result,
    by how much will that zone one one stop speed boost differ from a
    prolonged post exposure with same fog level?

    I keep hearing about more or less fog with prolonged post exposure.
    Anybody got a densitometer? Dan

  9. #39
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845
    Quote Originally Posted by jdef
    Thanks, Donald.

    I thought of the diffuser too, but I was most curious about the evenness of illumination from a single pinhole.
    Ah, okay, I missed what you were looking for. Assuming the diffuser is evenly lit, the intensity of light from the pinhole falling on the film plane is determined by the same inverse square law used to calculate flash exposures -- so you simply need to make the pinhole far enough from the film that there's less than 1/3 stop difference in the light intensity from center to corner, and ensure the diffuser is evenly lit. And, since you don't need to worry about image sharpness, you can simply make the single central pinhole larger if you find you need more light (which you probably will unless you use a 60 W bulb for a light source).

    Let's see, 1/3 stop is cube root of 2, about 1.26x light intensity, and the square root of that is approximately 1.12 -- so the pinhole distance must be such that the distance to the corner is no more than 12% greater than that to the center of the film. For 8x10 film, the film radius, center to corner, is square root of 41, 3.45 inches, so a right triangle with one leg that size musn't have more than 12% different between the other leg and the hypotenuse -- so 3.45^2 + X^2 = (1.12 * X)^2 and thus 11.9 = 0.26 * X^2 and X (the distance from film plane center to pinhole) must be at least 6.77 inches. I'd personally make it longer...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  10. #40

    Join Date
    Dec 2004
    Location
    Milwaukee, Wi
    Shooter
    35mm
    Posts
    3,242

    Pinhole if you want

    If you want to uaw a pinhole go ahead. I still think that an inline bulb dimmer is extremely easy to use and at about $10.00 frpm Home Depot very inexpensive. The lamp can be run from full on to virtually off.

Page 4 of 6 FirstFirst 123456 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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