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  1. #1
    metod's Avatar
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    Enlarger and UV filter

    Just curious, does B&W enlarger need UV filter? When I bought the Ilford filter set for my Opemus5, it came with a UV filter so I left it there permanently, right under the heat glass. Recently I had a little accident where I left the enlarger light on for a couple of hours (ouch!!) and the heat from the light might have damaged it. Should I replace it?

    Thanks.

  2. #2

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    Quote Originally Posted by metod
    Just curious, does B&W enlarger need UV filter? When I bought the Ilford filter set for my Opemus5, it came with a UV filter so I left it there permanently, right under the heat glass. Recently I had a little accident where I left the enlarger light on for a couple of hours (ouch!!) and the heat from the light might have damaged it. Should I replace it?

    Thanks.
    UV filter is to cut the ultraviolet rays... Is there any in your darkroom? Well, back college first darkroom there was like a rat hole, and one day I walked in I saw the sunlight coming through the ceiling gap... Unless you have that kind of issue (I'm kidding, but the incident was true), I don't think you need a UV filter. Maybe it helps to raise the contrast and protect the lens, but I'm not sure.

    And I had left my condenser-head enlarger on for about a hour or so this morning by total accident just like you with my fim strip still placed on the neg carrier. But I found no problem. I thought I might have burned the film or melted the plastic parts of the enlarger head because the whole unit was so heated up. But I didn't even see any damage. The neg was still as flat as it was before.

  3. #3
    Pragmatist's Avatar
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    Perhaps useful

    Metod, the filter is there to help keep focus on your prints. UV and Infrared light focus at different distances from visible light. Actually, there is a gradient all across the visible light spectrum. Photographic papers are primarily sensitive to the blue and green areas of the spectrum. VC papers rely on this sensitivity by combining two layers of differing contrast, each sensitive to one of these wavelengths. By modifying the amount of blue or green reaching the paper through the subtractive process, a contrast is arrived at.

    There are several things that add more UV focus shift to a VC print. Keep in mind that this shift can amount to over an inch in adjustment difference in some cases. First is the use of quartz halogen lighting. This is more of a culprit than tungsten or cold lights. Second is the amount of magenta filtration used to achieve contrast. The higher number filters or settings are usually the problem. The third factor is the lens. Different lens groups and coatings will handle UV quite differently. And then of course there is the paper.

    If an enlarger does not have one, most can be gotten as an add-on, or a Kodak Wratten 2E filter can be inserted. Replace the filter every year or two depending on your printing load because it will fade and be ineffective. This problem does not seem to affect fixed grade papers to the degree it does VC.

    Unless your filter is obviously warped, discolored, or damaged, there should be no issue. Simple warping of a plastic intermediate filter will not affect UV filtration, but it might "waffle" the light reaching the negative. Project a focused light circle on the board without a negative in place to check for this.
    Patrick

    something witty and profound needs to be inserted here...

  4. #4
    metod's Avatar
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    Pragmatist, thanks for your detailed info. I would never think that this filter could be quite useful. I actually have a halogen lamp in the enlarger and do VC printing, so I’ll better look for a replacement, just to stay consistent. The heat was quite considerable as it melted some of the Styrofoam in the mixing chamber. Now I also keep in mind that if a heavy magenta filtration is used, it is better to double-check the focus once filters are in place.
    Thanks.



 

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