Ideas for light blocking material for enlarger

Discussion in 'Darkroom Equipment' started by kbrede, Jan 22, 2013.

  1. kbrede

    kbrede Member

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    It was determined in another thread that the light source on my Beseler 23c II is too bright. I've done some research and find people recommending a light bulb with less wattage, but no one knows where to get such an animal. The other option is to use a ND filter.

    The filter compartment on the 23c is 5.5x5.5". I'd rather not mount a filter under the lens. ND filters of that size would cost more than the enlarger is worth. I'm going to need to dampen the light by 3 or 4 stops.

    Does anyone know of a more economical light dampening material, that won't affect the color of the light?

    Thanks,
     
  2. jbrubaker

    jbrubaker Member

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    What is the number of the bulb you are using now?
     
  3. kbrede

    kbrede Member

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    I'm on the road ATM so can't tell you the number. The original that came with it is a GE bulb. The one I bought online was specifically for my enlarger. Both bulbs have the same output.
     
  4. tkamiya

    tkamiya Member

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    If you are using 75 watts bulb, you shouldn't be having that problem in the first place.... What are the symptoms you are experiencing? Do you not get a reasonable exposure time with lens stopped down to say, f/8 or so?
     
  5. kbrede

    kbrede Member

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    It's 75 watts. The issue is having to print at f/22 or f/32 for a 8x10" prints.

    It's covered on this thread:

    http://www.apug.org/forums/forum48/114328-film-speed-test-winter.html
     
  6. kbrede

    kbrede Member

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    Last edited by a moderator: Jan 22, 2013
  7. MattKing

    MattKing Subscriber

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    A piece of unexposed or slightly fogged 8x10 film cut to size might serve as an appropriate ND filter.
     
  8. fotch

    fotch Member

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    That looks like the right bulb. Do you have a longer lens, maybe raising the height?
     
  9. Loren Sattler

    Loren Sattler Subscriber

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    Please explain what materials you are using such as paper, graded vs. variable contrast, film etc. I have the same enlarger and get 10-20 second exposures at f5.6 to f11 using Tri-X 120 negatives with Ilford variable contrast filters (usually #1-1/5 to #3) on Adox and Ilford VC papers with the standard enlarger bulb. If I were to print with a fast graded paper and a thin negative I can imagine possibly needing less light. I have flexible neutral density material available if I ever need it. The ND material comes in a roll. You cut a piece to fit into the filter drawer above the negative sandwiched with the VC filter. The ND material is not expensive and should be available at stores like B&H. However, I looked on their website tonight and could not find it. Maybe another member can provide the proper name and where to buy it.

    I wonder if your negatives are too thin?
     
  10. kbrede

    kbrede Member

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    It's an 80mm El-Nikor.
     
  11. kbrede

    kbrede Member

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    Hi Loren. I've covered all this here:

    http://www.apug.org/forums/forum48/114328-film-speed-test-winter.html

    It's a long thread. You could get most of the basics by looking at the first page and the last.

    That ND material sounds promising. What enlarger are you using?
     
  12. kbrede

    kbrede Member

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  13. MattKing

    MattKing Subscriber

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  14. Bill Burk

    Bill Burk Subscriber

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    You will enjoy having 2 or more stops of Neutral Density. If you have Color Printing filters, you could always add equal parts CMY to make ND.

    I personally use a 2-stop ND No. 96 Wratten gelatin filter when making small prints. It's only 2x2, and I simply drop it down inside the lens cone, right on top of the back of the enlarging lens. I would rather have 3 or 4 stops because still I have short exposure times.

    If you have a camera-grade ND filter, you could put it in the optical path. I've gathered from random threads the feeling that "filters in front of the enlarging lens are not that bad".

    While you're at it... do you have a "voltage regulator"? These units hold the voltage steady despite fluctuations of the incoming line voltage. Shouldn't be too expensive, and it can help rule out exposure variations caused by voltage spikes/drops that can happen between two prints that should look the same.
     
  15. Steve Goldstein

    Steve Goldstein Subscriber

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    As Bill suggests voltage regulator is a great suggestion and will insulate you against line variation.

    Another choice would be a "variac", a variable transformer. This takes in 120V from the wall plug and allows you to choose whatever voltage you want with a knob. A variac rated for 75W shouldn't be too expensive, and is probably available from Digikey or Mouser, both of which are highly reliable electronics distributors. I use a variac for the heating mat under my developing trays, it allows me to maintain chems at 70F in the winter in my otherwise-underheated darkroom.
     
  16. Loren Sattler

    Loren Sattler Subscriber

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    Kenton,
    I am also using a Beseler 23CII.

    As for the ND sheets, either density should work. The 3 stop material is probably more useful, but with the 1 stop sheet, you can cut multiple pieces and gang them for more density.

    I rarely print smaller than 8 x 10. I might need the ND filter if I printed smaller than 5 x 7.

    Over time you will probably expose your negatives with more density and solve the problem, or you will discover that your bulb is too bright for some reason causing the issue. Good luck.
     
  17. John Koehrer

    John Koehrer Subscriber

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    Is the condenser at the correct height? There should be a scale on the RH side of the assembly.
     
  18. kbrede

    kbrede Member

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    Hi John,

    Yep, the condenser is at the right height.

    Thanks,
     
  19. Richard Jepsen

    Richard Jepsen Member

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    I've used a 23c with correct 75w bulb and Ilford WT VC. Exposures typically f/11 and 15s. 120 film, under the lens filters, 80mm optic, 6x8 in prints.
     
  20. ac12

    ac12 Member

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    From what I understand, lowering the voltage on a bulb will change the color temp of the light.
    I do not know what that will do for VC paper. It may throw off the grades, so a #2 may print differently at full vs. reduced voltage.

    Since they do not make photo bulbs lower than 75 watts (that I know of), another option is to use a regular WHITE incandescent bulb of a lower wattage, say 40 watts or even 25 watts.
    I say this is not the best option because a regular bulb may not have an even coating of white to evenly diffuse the light. You also have to watch where the printing on the bulb is, vs the light path. If the printing is on the top end, and that is the path of light to the lens, you need to remove the printing from the bulb. I was considering this option myself, since a 75w bulb in my Durst M600 gives me a somewhat short exposure time of about 10 sec.
     
  21. MartinP

    MartinP Member

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    You didn't mention what exposure time you consider to be too short, but is 10-15 seconds about what you are seeing? Is the bulb designed for 120v and being run at 240v?

    Of course, it is possible that you want a minute of exposure time in order to dodge precisely - maybe an alternative to the ND filters is to make a 20" print with all the adjustments you want and then to re-photograph it, making a more or less straight print of the copy-neg.
     
  22. Greg Davis

    Greg Davis Member

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    I bought a 0.9 ND wratten gel filter on ebay for $1 and simply laid it on top of the rear element of my enlarging lens. Works great. It is a large 300mm Componon-S, so the 3 inch filter works well, for a smaller lens I would trim it down to size.