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

[ic-racer]

I had similar issues (http://www.largeformatphotography.info/forum/showthread.php?32852-Durst-L1840-Enlarger-8x10-10x10-Everything-you-wanted-to-know&p=448739&viewfull=1#post448739) with a cold cathode light. I made a center filter for it but eventually gave up and got a dichroic head.

[Craig Roberts]

I also observed this and it cost me a lot of hair untill... I replaced the tube, they don't last forever and that solved the problem. Craig

[5063]

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).

This is wrong. It is true with condensers, but not with coldlight. The light should be in the lowest position, as close to the film as possible.

[Robbie Bedell]

Craig, Thank you! That is the direction I am going. I have wanted to get the new Aristo V-54 tube, but I was afraid that after I make the replacement I might still have the same problem. But if it cured your woes maybe that's what I should do. The LED light I am looking at is about $270 vs. about $180 for the Aristo so staying with flourecent makes sense...

http://robbiebedell.photoshelter.com

[DennisD]

It's been years since I had my Arista cold lite head, ( identical to Fred Picker's Zone 6 head ), but, as I recall, the lite sat directly above the negative carrier in the compartment that previously housed the condensers. There was one diffusion disc and a filter to correct the light color. The light was very even.

I know my 5x7 Aristo head has a temperature /heat pad to keep the light even and start at full brilliance, but don't recall if the D2 version has the same. However, a bad heating pad could be a source of uneven light. Does the light even out if kept on continuously for a several minutes - I.e after the tube warms up ? - If so, the heat element, if there is one, or the tube may need replacing.

[Robbie Bedell]

Thanks Dennis. I did check the heater and it is working just fine..

http://robbiebedell.photoshelter.com

[Sal Santamaura]

Nature of the beast. See my post #36


http://www.apug.org/forums/viewpost.php?p=841843


in this thread:


http://www.apug.org/forums/forum172/64914-aristo.html

[Robbie Bedell]

Thank you Sal, In fact, during my research, I had come across your earlier apug posts. The strange thing here is that what I am experiencing is not just a little 'edge-dodging' but a lot. I would say it goes a good one-third the way toward the center of the photo and, I am guessing here, about a two stop difference from dark to light. What I am trying to determine now is that one: perhaps the bulb is going and two: will a new Aristo V-54 bulb help? I have been in contact with Louise at Voltec and am about to buy a bulb but I do not want to throw good money after bad....Robbie

http://robbiebedell.photoshelter.com

[Bill Burk]

Robbie,

What grade were you working at? I made prints from two different negs so far on my Aristo grid and I don't see the uneven lighting on those prints. Well, one print seems to have edge burn but I "did" burn that edge. It's just darker than I expected. The other print seems absolutely even.

Anyway, I was working at Grade 2 which may be less sensitive to the effects of uneven light distribution.

I hope I don't have to make a center filter because it looks like a good bit of work.

[Merg Ross]

Robbie, glad you contacted Louise at Voltec; she has been very helpful over the years. I have had the Aristo V-54 bulb on my DII for about ten years and it has performed beautifully. I added a dimmer, as the light is very bright, and also very even. Hope this will be the solution to your problem.

Merg

[RichardRitter]

Are the tubes in the clip?

[Robbie Bedell]

Bill: I was using no filter so my grade is about #2...

Merg: Thanks to your and Dennis' endorsement I feel confident about the new V-54 tube. I will be ordering one from Louise at the end of this week..

Richard: the tube is in the clip. But the rubber glue that holds it there has been tampered with, which makes me think that someone may have replaced the original tube. But it sure is hard to tell if it is old as it still looks plenty bright when it is on..

Thanks to all. You have been a grand help in all of this...Robbie

http://robbiebedell.photoshelter.com

[Kevin Crisp]

Robbie: Be extremely careful when replacing the tube not to stress the new or the old one. When they break you get mercury all over the place. The ones I have seen were held in with copper single strand twisted wire, but I do remember some silicone sealant too on the ends. Good luck. Good to hear that these parts are available again, after Aristo reorganized / changed hands, it didn't sound like that intended to go forward with the enlarger applications when I last talked to them. Maybe demand changed their minds.

[Robbie Bedell]

Thanks Kevin. I have a second, very old Aristo light that is worthless and I plan to practice with that before I do the real thing with the new tube on the good head...The new one does not have wire, just clips as Richard mentioned...

http://robbiebedell.photoshelter.com

[Kevin Crisp]

The tube is strong up to a point, but brittle and it snaps like a very fresh pretzel. Not that I would make a mistake like that.

[Robbie Bedell]

Well Kevin, you are correct! They are strong up to a point and then snap like a pretzel! The practice one I had came out like a charm. It was held in with the copper wire. But the good head I am going to use had the tube glued in with the silicon. Not so easy..snap! I am ordering the new one tomorrow and will be VERY careful putting it in. But it should not be so bad. I will not glue it in. Live and learn!! ..Robbie

http://robbiebedell.photoshelter.com