enlarger light fall-off

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maybe somebody can help me here. Every time i make a print there is a gradual lightening in the left one-third of the frame. Everything but this overexposed area is exposed properly. There is no overall inconsistency in the intensity of the light source, so I don't think it's the lamp. I have a condenser head. Thanks Tyson

-- Tyson Fisher (lowflyingfish@hotmail.com), February 21, 2002

Answers

You need to adjust the bulb in your enlarger so that it covers the whole negative.Usually you can loosen the road to which the bulb is fastened and move the bulb up and down and to the sides till you see even light ont the easel when there is no negative in the carrier.

-- Gudmundur Ingˇlfsson (imynd@simnet.is), February 21, 2002.

I agree that the above post is likely the problem, but it can also happen if your lens plane is out of parallel to the negative stage. If this is a problem, your lens may not have sufficient covering power to handle it & darkening will occur as you describe.

-- ernie gec (erniegec@stn.net), February 21, 2002.

Tyson the area is underexposed, not overexposed. Are you using the proper carrier for your enlarger? The reason that I ask is that if you don't there may be some play that allows having the neg off- center, and you'll run out of coverage. Also, are you sure that you have the right size bulb and condensers?

-- Wayne DeWitt (wdewitt@snip.net), February 21, 2002.

Tyson,

I agree with other posts that the bulb is probably not centered. Typically they are adjustable. According to my Beseler book: Insert negative in enlarger and focus image on baseboard or easel using full frame; remove negative and adjust light so it evenly illuminates the frame projected. I would also adjust the bulb back and forth to establish the total diameter of even illumination, then center it. The condensers are sometimes adjustable for centering (on my Beseler 45MCRX they are fixed; on the Beseler CB7 they are adjustable) Keep in mind the condenser SIZE will effect the SIZE of the circle of illumination. On Beseler enlargers, one size condenser is used for various formats (35mm through 4 X 5 for instance), ; the distance between the condenser and film carrier is adjusted by a second set of bellows and adjusted against a scale indicating the film format. Other brands, condensers have to be changed to match the format. Best of luck!

J. P. Mose

-- J. P. Mose (j.p.mose@lmco.com), February 21, 2002.


What focal length lens are you using? What negative size? If there is a mismatch here it could cause the fall off you are describing.

-- Ed O'Grady (ogrady@eximvaios.com), February 21, 2002.


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