Condenser light falloff

I was printing some 35mm b&w negatives earlier today and experienced some serious light falloff problems at the corners. I wonder if anyone can help. I was using a 45MX condenser on a 4x5 Beseler enlarger with a 50mm enlarging lens, aperture set at f/8. The print size was roughly 11 x 16", and I was getting more than 2 stops of light falloff at the ends, moreso on one side of the print than another. Alignment is OK. Everything is sharp throughout.

I tried adjusting the negative stage (the bellows section above the negative carrier) up and down, but light falloff did not seem to improve. Could there be something wrong inside the condenser head ... like a lens out of position or something?

If anyone is using one of these enlargers, I am missing the negative stage guide. Could you measure and please send me the distance settings to use to set the negative stage when printing a) 35mm, b) 2 1/4 sq and c) 4x5.

I tried burning in the corners but it was too difficult to get the burn even so that there was no perceptible difference in tone across the print.

Hi, George,

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Probably there is nothing wrong with your condenser head. Problem is, a condenser has a focal length, and must be reasonably matched to your enlarging lens to get even illumination. A 4x5 condenser is NOT reasonably matched to a 50 mm lens, and will send most of the light at the corners on to the inside of the lens plate instead of through the lens. Closing the lens down will make things even worse. One might suppose that by using just the center of the 4x5 field you would get very even illumination. Well, you will with diffuse light, but definitely not with condensers, not even with a diffuser above the condenser. Try a longer lens, if you can get the print size you need.

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Regards,

Per

Hi George..

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My ancient 45M has always printed 35mm evenly sharpness and evenly lit. It prints 35mm well with with my 50mm and 75mm lenses, but I use the sharper 75mm lens.

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When the red pointer on the condenser head is at the 35MM mark on the scale it is 6" above the negative stage. The distances on the scale are 4x5" - 1 1/4", 3x4" - 2 1/2", 6x7cm - 3 1/2", 6x6cm - 4 1/2", 35mm - 6".

The aluminium condenser focusing scale and two set screws are probably universal for all 45M variants, and should be available at a very reasonable cost from Beseler, website http://www.beseler.com.

The condenser focusing scale would be easy to make. The factory piece is made of 1/16" aluminium angle. The front is 3/8" wide and the side is 3/4" wide at the bottom tapering to 1/4" at the top. A 7" piece 3/8' x 3/4" or 3/4" x 3/4" or 1" x 1" profile etc would work well.

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Good luck getting your printer set up. Write again if you have more questions.

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Regards..

I don't know if this applies -- I use an ancient Omega D-3 and I don't know how it resembles or fails to resemble your enlarger but I have had similar problems...

In the D3 there is an additional condensor inside the lamp housing inside a little door that you might not notice if you did not know to look for it. It is between the lamp and the really large condensor. Instructions recommend to move it to this or that position for this or that focal legnth enlarging lens...I have found either the instructions or something else is wrong when I use 4x5 with my 135mm lens...instuctions reccomend placing the lens on the bottom shelf, after much experimentation I remove it entirely for more even results but I don't know why this is. Is there an additional condensor in your enlarger head that you are unaware of? Do you have the lens the proper distance from the neg? The Omega d-3 uses lens cones; other enlargers I have used include a Durst that used lens cones and a Beseler in which the lens board was moved up and down on a bellows like attatchment. Could this be the problem?

hope this can help

stefan