Omega Dichroic II mixing chamber IR filter with fogging

aconbere

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I’m chasing some contrast issues with a new to me Omega D5 enlarger with the Dichroic II head.

I have both the DD (4x5) and DB (6x7) mixing chambers. Both have IR filters and both seem to be in pretty bad shape. I’ve attempt to remove the haze with standard lens cleaner and have had no luck.

Other than KHB I haven’t seen any for sale.

Curious if other folks have experienced this, if you think it’s an issue worth repairing, and if you have any thoughts.

Thanks!
 

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ic-racer

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I suspect you are only losing fractions of a stop. How long are your exposure times?
 
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aconbere

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Not long, 20-30s at f16 on ilford fiber warmtone gets me to d-max.

Exposure times have been very workable, just battling low contrast and have been doing some clean up. Replaced some yellowed styrofoam in the mixer and noticed the filters.
 

ic-racer

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I'd just do as you are doing; clean them the best you can and not worry about them.

If contrast is low can you confirm the yellow moves all the way out of the path on 000 and the Magenta is totally covering at its max? How is the lens? Any fog? Are there any light leaks in the head? Fresh developer and paper?
 
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aconbere

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I can confirm yellow moves all the way out, and magenta all the way in.





The lens isn’t perfect but I don’t think it’s the issue.



The paper was purchased new by me in the last 6 months and stored in a cool dry place. The developer was freshly mixed from a newish jug of ecopro paper dev.

Now while I’m taking pictures here I do see that the filters themselves are pretty nasty! I’d blown some compressed air in there before but hadn’t really looked hard. I cleaned up the magenta the best I could, but I wonder if I should be pulling the filters out to give them a proper cleaning
 
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aconbere

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@ic-racer while I have you here. I replaced the lamp today and discovered the lamp socket is worn out. Is the best option the socket sold on KHB?

Also the diffuser on the DD mixer is worn (shiny in the center) but not on the DB mixer I have. Since my exposure times are fine do you know if I can swap them?
 
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ic-racer

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Socket replacement on old enlargers is usually a good idea.
I have not been into the DD and DB boxes, so not sure if the diffusers are the same.

To check your contrast generation from the Chromega Head, you can contract print a step wedge at maximum magenta and see how many gray bands you get. That will let you know if the head is generating adequate contrast and eliminate any loss of contrast from the lens or from flare or light leaks.

Be careful cleaning the filters. The order of re-assembly of the whole unit is very important. Lots of springs and spacers.
The surface of the dichroic filters may be damaged like the IR filter and not clean up. But they still may work fine.
 
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aconbere

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Heard, I’ll avoid any disassembly until after I do some testing. In the mean time a qtip and some lens cleaning solution made it much better from what I can see.

Ordered a new socket. The one I have is working, but the mica cover has cracked and the connector for one leg is loose. There’s no evidence of severe arcing on the old bulb though. I bent the connectors back into shape with some tweezers and got the new bulb

I feel like I could probably fully repair the socket with some deoxit and kapon tape, but that might be a project for another day.

- A
 
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aconbere

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Heh, about 20 min into doing my tests my new bulb burnt out!



So I only got one test print before the bulb started getting weird and subsequent tests don’t seem valid. At 150 magenta (not max but whatever 150 means) I get 8.5-9 steps. But I’d love to compare it to Y41, M32. Guess that’ll have to wait a bit for shipping.

I talked to the seller and got two new bulbs on the way, but now I’m even more distrustful of the socket. I picked up two of those off ebay but curious if folks know where to find them new? They appear to be a standard bipin halogen socket rated for 250W but I can’t find anything on the consumer market that matches that.
 

Doremus Scudder

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Replace the socket. The arcing from the bad socket burns out bulbs due to the voltage surge. Make sure contacts are clean.

Doremus
 
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aconbere

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Dichroic on the left, ilford filters on the right. “C2” on the top “C4.5” on the bottom.

I didn’t get all the exposures lined up the same, but the good news is that the number of steps in the dichroic and ilford tests line up perfectly.
 

Donald Qualls

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DREW WILEY

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The CMY filters in general are quite dirty and have no doubt lost some of their efficiency. They certainly look geriatric. But you have to use extreme care cleaning old ones; the coatings might be fragile. Dichroic filters don't fade per se, but with colorheads that old and corroded, a certain amount of spalling off of the coatings has undoubtedly occurred, along with the grime build-up issue. It's obviously been previously used in an overtly humid environment, probably a poorly ventilated sink room.
 
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aconbere

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Yep, I’ve got Magenta pretty clean as it’s easy to reach without messing with anything. The question now is wether it’s worth attempting a disassembly to clean the other filters when it seems I’m able to get pretty reasonable results
 

DREW WILEY

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That's good. Magenta is the most important one if high contrast is your priority. And you could access at least some of the other two filters just by dialing things out of the way and using a Q-tip. How much further you might want to risk it is up to you. I'd probably stop at that point if only VC printing is in mind, and not color printing per se.

In terms of other tuneup issues, avoid any lubricants which could potentially leave a flammable residue.
 

ic-racer

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Once you start cleaning, you may find the filters pop out and will need to be re-glued.
 
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aconbere

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Wild thing happened earlier this week.

I’m taking a class on making custom photoshop curves for digital negatives and as part of that I’m doing dmax testing of Ilford MGRC paper with the transparency we’re using.

I did the testing once with the schools enlargers and dev and then repeated the tests at home.

In doing so I think I found that my home tests just were NOT reaching Dmax. But it also just seemed like, they weren’t done developing?

I’m using Eco Pro developer and they list two dilutions and times for their dev with RC paper. 1+14 for 60-90 seconds ans 1+9 for 90-120 seconds. Being the thrifty boy I am I’ve been using 1+14 for 120 seconds.

Since I was trying everything anyway figured I would try 1+9 for 120 seconds and the results are DRAMATIC.



So maybe my issue has just been my developer giving inconsistent results and this is just a lesson of testing everything?
 

Doremus Scudder

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Well, you've certainly found your problem!

Developer is relatively cheap when compared to paper, better to use strong enough and long enough and toss it before it begins to exhaust than vice versa.

You'd do well to keep that Dmax test strip hanging on the wall by your print viewing area to compare to the blacks in your future prints.

Best,

Doremus
 
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aconbere

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More than a little embarrassed by these results

But progress is progress.
 

MattKing

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aconbere said:
More than a little embarrassed by these results

But progress is progress.
Click to expand...

Embarrassment is unnecessary.
One of the downsides of this internet based learning community is that it provides a fundamentally different feedback loop - different to a great degree from the sort of experience one has when one seeks help in person from other people.
If you were at a meeting of my Darkroom group and seeking help with your issue, it would have been much more likely that someone would have suggested changing the developer. And if we were meeting in your darkroom, we would probably have tried it right there.
 

ic-racer

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Since you tested it, you now know your color head is performing as it should.
 
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