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  1. #1

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    Very long enlarging times, 2-3 minutes

    Hi everyone. I've recently started enlarging at home. I bought a Omega Chromega B enlarger with a 3.5 50mm omegar lens. With 60 magenta filter my enlarging times are anywhere from 2 minutes to 3 minutes with various densities at f/8. I know that my times should be much shorter! 10-30 seconds right? My times are much too high. I believe the enlarger has 6x6 mixbox also, not 4x5. My blub seems very bright when I open the head up but all that light must get lost somewhere. Does anyone know what's wrong? I was considering a new blub but it seems so bright right now.

  2. #2
    Lopaka's Avatar
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    If you are using a 50mm lens I assume you are working with 35mm negs. Enlargers that use mixing boxes spread the light evenly over the area of the neg size they are designed for. If you are using a 4x5 mixing chamber you are spreading the light too thin - you need a 35mm mixing chamber to concentrate the light to the neg size. And welcome to APUG!

    Bob
    "I always take a camera, That way I never have to say 'Gee, look at that - I wish I had a camera'" -Joe Clark, H.B.S.S.

  3. #3

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    I think it's a 6x6 or 2.25 mixing chamber. But I'm really not certain. How do I verify? I use 35mm.

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    The opening in the mixing chamber is just a tad bigger than the diagonal of the negative it is intended for. Thus, the opening on the 4x5 chamber would be about 6" and for a 6x7cm negative would be about 8cm.

    But, I only see about a 1 - 2 stop difference if I use the wrong mixing chamber. So, I doubt if that is your problem.

    PE

  5. #5

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    The Chromega B is a medium format enlarger that doesn't go beyond 6x6 in some models, according to Classic Enlargers.com (http://www.classic-enlargers.com/omega_b22_enlarger.htm).
    Though a 35mm mixing box would help, it's not the sole reason you're getting such long exposure times. The guy that runs Classic Enlargers has a q and a forum, which would be another good source of help. Harry has been servicing Omega enlargers longer than some folks here have been alive.
    Have you done any tests with white light exposures? Is the mixing box in good shape? Do you have more than the magenta filter in place when your are making these exposures? Especially do you have any cyan dialed in along with yellow? Using all three filters gives you neutral density filtration. Finally, are you using a VC paper?
    I don't know if the Chromega B has an attenuator, but if it does, that might be blocking the light.

  6. #6

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    Thanks for the replies. I only have magenta filter on. I'm using ilford multigrade IV rc de luxe. I will try Harry too. I didn't really do any white light tests. I think the mixing box is fine. I don't think servicing is worth it, I paid 40 dollars for the whole setup. Perhaps if I can't get it brighter I will look for a normal condenser setup. Staccato sentences, hehe.

  7. #7

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    In theory, cyan filtration will have no effect on most B&W papers; cyan filtration just removes red light, to which most B&W papers are insensitive anyway. Using both magenta and yellow filtration will increase exposure time, though, so if both are set that could be an issue.

    A few ideas of causes come to mind:

    • Paper -- What paper are you using? Some papers are much faster than others. I tried some Slavich Bromoportrait 80 recently, and it's very slow compared to the Agfa and Foma VC RC papers I normally use.
    • Dirt/discoloration -- If the mixing box is dirty or discolored, that could greatly reduce the amount of light reaching the paper. My first enlarger (a Durst C35) had a mixing box that was slightly yellowed with age. I don't think this caused me great problems, but more severe discoloration could. Similarly, a lens that's gunked up would cause problems, and perhaps not just long exposure times!
    • Aperture problems -- Check that the lens's aperture is working correctly. If it's stuck too small, this could be the source of the problem. Remove the lens and look through it to check the aperture operation (and check for dirty lens elements).
    • Filters -- Check that you don't have filters in the enlarger's filter drawer (if it's got one). A neutral density (ND) or other filter could be reducing the light reaching the paper.
    • Development -- Try developing your paper for a longer period of time. Chances are this isn't the only problem (you'd probably never get a satisfactory black if you were seriously underdeveloping), but modest underdevelopment could be exacerbating some other problem.


    Suggestions by others -- mixing box issues, for instance -- are also worth checking. I don't mean my list to be exhaustive.

  8. #8
    thebanana's Avatar
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    Could also be the wrong bulb.
    "While you're out there smashing the state, don't forget to keep a smile on your lips and a song in your heart!"

  9. #9
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    A cyan filter, dialed in with an M and Y will reduce exposure by a factor equal to the density of the neutral density of the filter pack. Mainly, this is due to the impurity of the cyan filter iteself contributing density to the light even though the paper cannot 'see' the filter itself.

    PE

  10. #10
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    . I bought a Omega Chromega B enlarger with a 3.5 50mm omegar lens. With 60 magenta filter my enlarging times are anywhere from 2 minutes to 3 minutes with various densities at f/8.
    ******
    Are you sure there is not some other filter in the light path? And, of course, your paper developer is fresh, right? What paper developer are you using? I sure hope you are not using D-76 or some such film developer instead of paper developer. Sounds strange, but many of us have done that by mistake or for experimentation.

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