Help with Zone IV coldlight!

[Robbie Bedell]

I am pulling out what little remains of my hair..I am not new to cold light and this is not about filtration, which is not the problem. I recently got a like new "newer" 4x5 Zone VI cold light for my D2. I installed it and have been been relatively happy printing 35mm and plan to print with a variety of formats... But yesterday I made a test just for the heck of it and printed a piece of paper without a neg. in the carrier. I saw some pretty good light fall-off with the small neg. So I set up for 4x5 and made the same test on a piece of paper without a neg. Yikes! I have never seen such uneven light. Hot spot, fall off, no matter what you call it, it is very severe. I tried a number of things, including making sure the bulb is square with the carrier, removing the shiny metal collar that separates the two white difusion discs and adding a ring of black felt around the inside of the lamp housing. The problem is consistant. Nothing helps...I know there is a way to make a lithe film graduated filter but I really don't think I should have to go that far. This is my second cold light. I used an old one in the 80s and never had the problem, but maybe back then I was too dumb to notice! I eventually want to get a new Aristo V54 tube but if I don't solve this problem I don't want to spend the money...Thanks in advance! Robbie

http://robbiebedell.photoshelter.com

[Jay Wolfe]

What lenses are you using for the negative sizes you tested?

[Kevin J. Kolosky]

you have to change the configuration of the top bellows when you switch to 4 x 5. At least you do on the Beseler unit which I have. (you have to move the light father away from the negative the larger the negative gets).

[Robbie Bedell]

Thanks guys. Jay I am using a 135 Componon S for the 4x5 and 50 and 80 and 100 of the same make for my various formats...I just read somewhere that Fred Picker did not recommend a 135 mm lens for 4x5 and his cold light. The only lens I do not have is a 150. But it is still pretty bad even with the 50..This is driving me crazy!! Could the bulb be bad?

Kevin, Thanks, but I am using an Omega D2...

http://robbiebedell.photoshelter.com

[Robbie Bedell]

Jay. I just tried with my 80 componon S with the square carrier and it is STILL very bad...

[lenser]

Robbie,

This is a wild theory, but give all lenses a try for tests with NO carriers in the enlarger. As I said, it is a wild thought, but I wonder if the carriers, without negatives, are acting like some sort of a huge pinhole and concentrating brightness to the center while shading the edges, thus creating a sort of vignetting effect. Or if the edges of the carriers are causing an extra reflective effect without a negative in place to additionally scatter the light. If your prints without the carriers are even, that would seem to bear out that somehow the empty carriers are creating this odd fall off.

[Robbie Bedell]

Hi Tim, I just tried what you suggested. I left the 80 on the enlarger and removed the carrier. Wow, it is so bad I don't even have to make a print. It can easily see it on the easel. And this is focussed on 8x10 paper. I might add that I use the appropriate cones for 6x9 and 4x5. I feel like throwing all of this stuff away and trying one of those new LED heads.. I bought this Zone VI head on the Bay. It is painted black on the outside and looks as if it has hardly been used, but it would not surprise me if someone swopped out a good tube at one point. But this one sure looks nice and bright...

http://robbiebedell.photoshelter.com

[Bill Burk]

Robbie Bedell,

I, too, use a D2 with cold-light and 135mm lens for 4x5. I recently suspected the exact same thing you reported so I picked up an Aristo grid-based cold light head. It seems smoother than the old Omegalite-D (ring-lite based head)... But I am not convinced that I have even light distribution yet.

Is there anything between the grid lamps and the negative (carrier)? I added a piece of opal glass that didn't come with the head and I'm sure that helped...

Meanwhile I feel the grid is an improvement. I havent done a blank sheet test to verify.

[Deane Johnson]

Does it have the diffusion disc below the tubes?

[Robbie Bedell]

Bill, Nothing between the lamp and the carrier. It sits right on top of the carrier.

Deane, Yes, there are actually two diffusion discs, one on top of the other...

Thanks to both..

http://robbiebedell.photoshelter.com