LPL 7700 Pro Condensers

Discussion in 'Darkroom Equipment' started by shmalec, Mar 2, 2010.

  1. shmalec

    shmalec Member

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    Hi there,
    first post on this site, expect there will be many more.
    I just bought a LPL7700 Pro. It's a 6x7 condenser enlarger for black and white only. It is meant to have 3 condenser lenses. All three are used for 35mm and only two are used for MF. The one I've purchased second hand is missing the third condenser for 35mm work. If I use the medium format condenser setup with the 50mm lense, is this going to cause uneven density of light across the negative or will it just require longer exposures? If you have this enlarger, how do you use it? Do you move the bulb to the 35mm position and add the third condenser or do you just use MF setup with the 50mm lense? I will be doing both MF and 35mm work.
    Cheers
    Alec.
    PS If you have one of these (No.3) condensers and would like to get rid of it, I would be very interested. :smile:
     
  2. Jon Shiu

    Jon Shiu Subscriber

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    I don't know the answer, but a third option would be to use the lens for MF to print your 35mm, although that would would limit the maximum size of enlargement.

    Jon
     
  3. Tim Gray

    Tim Gray Member

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    On my 23C, I can adjust the spacing of the condensers for different formats (35mm - 6x9). If I'm doing 35mm with a 50mm lens, I can and often do just leave it on the 6x9 setting. The light distribution is even across the whole field, just not as bright as if it were on the 35mm setting. So, printing times are longer, but I don't have a problem with long printing times at all. Often, the opposite.
     
  4. ic-racer

    ic-racer Member

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    If you do 35mm like that but just make sure you use the 80mm lens. You just won't be able to make real big prints, but it will work perfectly like that until you can get the other condenser.
     
  5. ath

    ath Member

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    I have the LPL 7700 with condensors and deliberately use only the two condensors for 80mm with a 50mm lens. No falloff visible and it is even brighter than with the third condensor (which is weird).
     
  6. Tim Gray

    Tim Gray Member

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    Again, the way I look at it, if there is no light fall off for 6x7, there can't be any for 35mm. Just use it as is. Times might be a bit longer, but you should be able to use your 50mm or 80mm lens.
     
  7. ic-racer

    ic-racer Member

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    Condensers are focused based on the focal length of the projecting lens and the lens-to-negative distance. That is different than a diffusion mixing box, which is sized according to the film format and is independent of projecting lens focal length.
     
  8. ath

    ath Member

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    Yes, but it doesn't seem to matter that much with this specific enlarger.
    Might be the big illuminated area of the frosted bulb in contrary to a point source.
     
    Last edited by a moderator: Mar 3, 2010
  9. shmalec

    shmalec Member

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    Thanks folks. I was initially inclined to agree with Tim and Andreas, that an evenly illuminated 6x7 neg could be replaced with an evenly illuminated 35mm neg and the lense changed. But now I'm not so sure. I had a look last night and there does seem to be some slight fall off using the 50mm lens. However, it is a very small, cheap, plasticy looking Besler 50mm f3.5 lens. So it may be the lense. Anyway, the column is pretty tall so I think I can print to about 16" with the 80mm rodenstock, so this is about as big as I'd go with 35mm anyway.
    Any ideas on where I might pick up the last condenser?
    Cheers, Alec.
     
  10. Jon Shiu

    Jon Shiu Subscriber

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    Here is the answer I got from OmegaSatter.com
    Our part number is LPL32313430 retail price is 60.95 and should be purchased at your photo dealer of preference.

    Jon
     
  11. ic-racer

    ic-racer Member

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    You are right, that indeed could be the case. Most "condenser" enlargers are somewhere between a perfectly collimated point source and a diffusion source. So, on the LPL the focus of the condensers may not be super critical.

    I guess most important is to check various combinations of the condensers and see which combination actually is the most even under your conditions.

    I high contrast print with no negative can be very revealing :wink:
     
  12. Tim Gray

    Tim Gray Member

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    This is obviously academic if you have an 80mm lens that you can use and gives you sufficient enlargement, but your 50mm lens might be at fault. Were you trying this at full aperture?

    Also academic, but isn't the point of the condensers to evenly illuminate the negative? Even a blank negative should add a fair amount of diffusion to the optical path. I would think that would more or less interfere with any optimization of the condensers to match them to the lens-to-negative distance and projecting lens focal length.
     
  13. ic-racer

    ic-racer Member

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    You are thinking of a diffusion head. Condensers produce collimated light in which it is focusing an image of the top of the bulb down toward the lens with most of the rays traveling in the same direction. If the enlarging lens (or the bulb) is not in the correct position then many of the light rays bypass the lens and the effect is dimness. If you put a diffusing screen above the negative, you have now evened out the light so any lens position is OK but it now is much much dimmer because the rays are scattered about.

    A clear piece of negative film will allow essentially all collimated rays to pass through in their original direction and is not a diffuser.
     
  14. Tim Gray

    Tim Gray Member

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    This was the part I was curious about. While clear film does is clear, it definitely does diffuse the light some. However you are right - not enough to really make a difference.