Uneven illumination Omega D5XL

[Pieter12]

Upon making some 11x14 prints of a scene that has a pretty flat sky, I discovered that one side--one corner especially--is darker (that is the print is lighter) by 1/2 stop or more. This is in comparison to an 8x10 print I made earlier in the week.

Let me explain a couple of things. The original is 2-1/4 square and the 8x10 was made with a 135mm lens, as I like having ample room to dodge & burn between the head and easel. The 11x14 was made with a 90mm lens. Condensor and bellows were adjusted appropriately for each lens. I thought it might be an issue with the 90mm, so I tried a 105 that I have. Same issue. I then reverted to the original 135 and the hot area no longer showed up on the print, it printed like the 8x10.

Another twist, and I suspect the culprit, is I use a small, halogen bulb instead of the oem one. It gives me a crisper print, sort of part-way to a point light source. I think it might not be perfectly centered in the lamp housing, but I wonder if there is a relatively easy method to check it and line it up.

Thanks in advance for your help and advice.

 

[koraks]

I would start checking alignment of the light source vs. condensers as well as centering of the lens below the condensers. A spot meter would be nice, but in a properly darkened room (no safelight!) you can get quite far just checking things visually. Or of course running some test prints, but that takes a bit more time.

 

[Lachlan Young]

I suspect the culprit, is I use a small, halogen bulb instead of the oem one. It gives me a crisper print, sort of part-way to a point light source. I think it might not be perfectly centered in the lamp housing, but I wonder if there is a relatively easy method to check it and line it up.

I'd try it with a correctly shaped bulb first and see if the problem goes away - point light sources tended to have much more extensive ability to precisely position the bulb than regular condenser heads - which can themselves be pretty fussy about bulb shape.

 

[mmerig]

Recently, I had a similar problem with an Omega D2, using separate condensers for different formats, and the PH211 bulb (a frosted 75 watt incandescent). After replacing a burned-out bulb, I had a strange pattern of light density, and it got worse when I stopped down. It turned out that the new bulb's coating/frosting was too thin, and the filament was showing up. I had another new bulb, and the same thing happened, just a different pattern, and it rotated if I rotated the bulb. When I held up the replacement bulbs to a bright light, I could see the filament through the frosting, but not on the burned out bulb. I ordered two new bulbs and they are fine.

There is no obvious way to adjust the bulb's position in the D2's head.