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  1. #1

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    Exposure Times with LPL Enlarger

    I have posted this question several times in the distant past but never really got a satisfactory answer if, in fact, there is one.

    I am currently using an LPL 4by5 enlarger with the VCCE head. Unlike the color head the VCCE head does NOT have a light attenuator. I am using a 150mm Rodagon N lens for 4by5.

    I test my films using the zone system and develop for a diffuser light source. In other words the negatives are denser than I would develop for a condenser system. I use a densitometer to check my zones and usually test for zone 1 and zone VII.

    I am more than satisfied with the results. The prints are great, but here's my problem. My exposure times are too short. I use both Ilford and Agfa (RIP) MC fiber. For an 11/14 print my times are about eight seconds at f 11!!! This wether I am printing 4by5 negatives with the 150 mm or 6by7 negatives with a Rodagon N 90 mm. I would have hoped that they would have been about 12 seconds at f8. No time to burn and dodge and, although f11 seems fine on these APO lenses, I would rather use f8. And little chance I can use graded with these times and the filters switched out.

    I have the XLG model which has a 250 watt halogen bulb. You CAN NOT REPLACE THE BULB WITH THE 200 WATT USED IN THE SMALLER MODEL. It will not work, has a different footing an will blow the lamp.

    The reason for the caps is that some have suggested a different bulb or that in fact there is an attenuator in the head. I can assure you that neither solution is possible.

    I have printed some of the same negatives in the school darkroom where they have Omega condenser enlargers and I get normal times, i.e. 12-14 seconds at f8.

    So, any suggestions? One very knowledgeable individual has told me that the light transfer from the APO Schneider and Rodenstock lenses is much greater than with the Nikkors. He has measured same.

    I could go with neutral density filters but will only use that as a last resort.

    I keep getting the feeling that I am missing something. I’m stumped. HELP!

  2. #2
    Muihlinn's Avatar
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    the atenuators built-in color heads used to be ND filters...
    What about a light intensity control circuit?
    Luis Miguel Castañeda Navas
    http://imaginarymagnitude.net/

  3. #3

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    I don't print 4x5 negs, but when I run into the same problem, I just have to close down the F stop to cut down the amount of light and/or use a longer lens to get more height on the enlarger.

    What are the maximum F stop numbers on your lenses? Don't close all the way, though.

  4. #4

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    The short answer is expose your negatives by another stop. This will build your overall density. Recheck your density range after doing this to see if your development times are still proper.

    This should increase your enlargement exposure times with no need to use ND filters in the enlarger light path.

    Don't be anal about what Adams wrote on Zone densities. You might try for a 1.00 density range (high densities minus low densities....not minus FB +fog) That will get you into the ball park.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  5. #5
    raucousimages's Avatar
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    I have the same enlarger without your problem. The only thing I can think of is that the Focus/Print lever is not kicking the filter in front of the light. You should cee a notiable drop in light when you switch from Focus to Print. Or is your bulb bad? I have had bulbs get very bright just befoe they go out. Other than that I dont know what to tell you.
    DIGITAL IS FOR THOSE AFRAID OF THE DARK.

  6. #6
    raucousimages's Avatar
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    One more Idea. Do you have the correct mixing chamber? I think there were different chambers for smaller formats, this might change somthing.
    DIGITAL IS FOR THOSE AFRAID OF THE DARK.

  7. #7
    Lopaka's Avatar
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    Here is what the inside of the color mod looks like when the brightness attenuator is switched on. It is thin metal plate with uniform holes across the opening to reduce the light evenly across the entire opening - so as not to bias any filtering inside the module. Hope this helps.

    Bob
    Attached Thumbnails Attached Thumbnails mod1.jpg  
    "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.

  8. #8

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    Thanks for all the suggestions

    1. Yes, the focussing lever is working and I notice a significant decrease in light when it is thrown before making exposure.

    2. I don't want to develop for even more density because my high zones will blow out.

    3. Thanks for the picture of the metal attenuator used on the color head. This is certainly one solution, taping such a piece of metal over the hole into the diffusion chamger.

    4. I could go to f 16 but I just wonder if this is a compromise that is not justified if one has a good lens to begin with. And what happend when I try to print graded paper? Way too much light.

    At any rate, I will never buy an enlarger again that does not have some sort of attenuation possibilities so that one can stay at critical f stop while just adjusting the time. At this time I am looking for an 8 by 10 (ugh!) enlarger anyway so I may make the change then. I have no other fault with the LPL but I do think that the b&w head could have been designed better.

    So my next thread will be your thoughts on a two enlarger darkroom!

    Thanks again fellows

    dick

  9. #9
    david b's Avatar
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    Do you really think you can see a difference going from f11 to f16? Have you done a side by side comparison yet?

  10. #10

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    Probably not, but I really like the prints I am getting and don't really like the idea of being forced to use a particular f stop.

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