Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,672   Posts: 1,481,835   Online: 1126
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 16
  1. #1

    Join Date
    May 2006
    Shooter
    Medium Format
    Posts
    341

    Limiting light output...

    Hi all,

    I've started playing with contact printing my 4x5 negs for fun. My printing experience (was) extremely limited, but after some time I got good output and am pleased.

    Except for one thing....

    My bulb is a 15w bulb, in a desk lamp with a rounded cone (sort of a parabola shape), about 3' above the negative.

    The printing paper suggests a 7.5w bulb at least 4' above the paper, but I couldn't find anything quite that week.

    End result:
    My exposure time on thin negs is about 1s, dense negs about 5s. I'd like to slow the process down, so that even the thin negs require several seconds of exposure, so that I could burn and dodge.

    Question:
    Any ideas on a cheap simple way to dim the light? I was thinking nuetral density filter - perhaps a tinted shield from a motorcycle helmet, cut to shape and taped in place on the lamp (since the exposure will be short).

    Any better ideas before I spend money?

  2. #2

    Join Date
    Nov 2004
    Location
    Italia
    Shooter
    Multi Format
    Posts
    4,680
    Move the bulb. Say lift it to 4.5 feet.

    Remember light increases/decreases with the square of distance or something like that -)

  3. #3

    Join Date
    May 2006
    Shooter
    Medium Format
    Posts
    341
    I'll try that first. Just gotta think on how... it's in the bathroom, on a countertop, so I'll have to put a box under it or something.

    Thanks.

  4. #4
    DWThomas's Avatar
    Join Date
    Jun 2006
    Location
    SE Pennsylvania
    Shooter
    Multi Format
    Posts
    2,145
    Images
    62
    I know you can buy 7.5 W bulbs with a standard household screw base, that would give you a little less light. Years ago I did some contacts using a radio pilot light type bulb hooked to an old toy train transformer from my (massive) junk collection -- that makes it almost point source.

    (Of course I am a compulsive tinkerer. )

    DaveT

  5. #5
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,079
    Images
    20
    Weston had his bulb on a peg board so it could be set at different heights (you could even space them by stops if you wanted), and he had some cloth over the bulb, which must have acted both to diffuse the light and reduce output.

    If it wouldn't generate too much heat and present a fire hazard, you could put one or more layers of cloth or paper under the bulb.
    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

  6. #6
    David Brown's Avatar
    Join Date
    Feb 2004
    Location
    near Dallas, TX USA
    Shooter
    Medium Format
    Posts
    3,173
    Images
    5
    7.5W bulbs are available. If the "desk lamp" in plugged into an outlet, you could also buy a dimmer, perhaps incorporated into an extention cord, that would give you quite a bit of control over the level of light.
    David
    Taking pictures is easy. Making photographs is hard.

    http://www.behance.net/silverdarkroom

  7. #7
    MattKing's Avatar
    Join Date
    Apr 2005
    Location
    Delta, British Columbia, Canada
    Shooter
    Multi Format
    Posts
    11,566
    Images
    59
    Have you tried bouncing the light off the ceiling?

    Matt

  8. #8

    Join Date
    May 2006
    Shooter
    Medium Format
    Posts
    341
    All,

    Thanks for the ideas.

    Going to try, in order:

    Bouncing light off ceiling because it's easiest. If that doesn't work, then:

    Find a 7.5w bulb. If that doesn't work, then:

    A variant of David A. Goldfarb's idea... I'll try to restrict the light by making an aperture. I know the opening size of the existing cone, I can calc out a circle with half the area and thus half the light. Since we're talking just seconds, and the 15w bulb doesn't generate much heat, it should be OK.

    Thanks!

  9. #9

    Join Date
    Dec 2006
    Location
    Apple Valley Ca.
    Shooter
    35mm
    Posts
    39
    Doug,
    I had the same problem w/my omega B-600. I shot some B&W 4x5 exposures of a flat white wall using the negatives to create a neutral density filter and cut and inserted the 'filter' in the enlarger. Exposure times are now up around 4 sec for Ilford MG IV satin and about 8 sec for MG wartmtone glossies.

    best regards

    john

  10. #10

    Join Date
    May 2006
    Shooter
    Medium Format
    Posts
    341
    Hi all,

    John - good idea.

    But bouncing the 15w light off the ceiling worked like a charm. Negatives that are very dense (very overexposed winter scenes) around 20s, normal density negs about 5s, thin negs around 1s.

    Thanks, all - good to have reasonable times & control.

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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