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Morten
18-May-2017, 13:49
Hi,

I have a Durst 138 with the cls301 colorhead, the enlarger are from the mid 70's.

Today I printed some samples at various grades to use for testing a diy LED head on a Focomat 2c, work in progress.

Looking at my test prints there are very little difference between the grade 3 and grade 5 print from the durst. Had expected a wee more.

Thus the question, do a color head deteriorate with age? Or go out of calibration? (Two lamp head)

Best regards
Morten

Bob Salomon
18-May-2017, 13:56
If yours has dichroic filters then no. If they have some dupe of died or gel filters then yes, they do.

Michael Rosenberg
18-May-2017, 13:56
Morten,

The dichroic filters will degrade with age, and depending on the age/use of the enlarger it can vary. Likewise the age of the bulbs matter; I use to routinely replace the bulb in my enlarger yearly. You can see the difference between a new and old bulb when printing, so you may want to do that first. If you can't get the dichroic filters you can get polycontrast filters for below the lens.

Mike

Morten
18-May-2017, 14:35
Michael, Bob

Thank you for the information. The enlarger spent its first 30+ years as a workhorse in the major professional lab here in Norway, before they shut down. Thus it might have seen a large number of negatives probably most color.

Brgds morten

Jac@stafford.net
18-May-2017, 14:55
Morten,

The dichroic filters will degrade with age, and depending on the age/use of the enlarger it can vary.

Dichroic filters work through physical filtering rather than by color dyes. Are you SURE they degrade, and by how much? The issue you mentioned was likely caused by the light source, not the filters.

ic-racer
18-May-2017, 15:46
Looking at my test prints there are very little difference between the grade 3 and grade 5 print from the durst. Had expected a wee more.

How did you do the test? Did you verify the filter covers the light source entirely at "Grade 5?" I hope there was no lens involved in the test, otherwise you are testing the lens for flare.

Morten
18-May-2017, 16:13
Well, lets rename this from "test" to "reference" :-) the basic idea was to have some comparisons prints from a (assumed) established system vs the new experiment system.
- no I did not verify that the filters covered the light source, I did just dial in the filter settings (130Y/M ilford scale)
- did a teststrip first on each grade, trying to establish the highlights on similar level before the flat print
- both lamps changed within the last 12 months, if this matters. Only a few enlargements since then
- negative perhaps a bit more on the contrasty side, however more notable differences from grade 0 to grade 3 than from grade 3 to grade 5
- yepp, lens involved.. :-)

Perhaps some misalignment of the new lamps?

Luis-F-S
18-May-2017, 16:20
If you routinely need to print on grades 4 & 5, instead of worrying about the Dichroics, I'd be more worried about my film speed and developing time. Correctly exposed and developed negatives should print on grades 2-3. I can't say if I can reach Grade 5 on my DeVere 5108 because I've never needed to. L

Morten
18-May-2017, 16:29
If you routinely need to print on grades 4 & 5, instead of worrying about the Dichroics, I'd be more worried about my film speed and developing time. Correctly exposed and developed negatives should print on grades 2-3. I can't say if I can reach Grade 5 on my DeVere 5108 because I've never needed to. L

I agree that is the aim, and where I hope to be most of the time, but as said this was in the interest of "reference" for a new experimental VC head. And the results somewhat made me wonder. In addition I'm planning to play a bit with split grade printing, thus high grade (5) and low grade (0) easily available would be a benefit.

Peter De Smidt
18-May-2017, 16:33
Yes, the filters do fade. They did in my De Vere 504. Grade 3 was the max with the old filers. New filters fixed the problem without doing anything else. Diffusion material can also yellow witch would cause lower contrast. On my enlarger, the color filters are between the heat absorbing glass and the lamps, and so they were nuked with heat. It's possible, I suppose, that old De Vere filters were less saturated than newer ones, but that seems unlikely.

Bob Salomon
18-May-2017, 16:41
Dichroic filters work through physical filtering rather than by color dyes. Are you SURE they degrade, and by how much? The issue you mentioned was likely caused by the light source, not the filters.

Dichroic filters have a metallic coating that is deposited on the glass in a vacuum. There is little or no chance of them fading. However, lamps age, diffusion chambers can become something else then their original color, if it was around smokers that could create color changes over time, if your enlarger is not voltage stabilized then changes in line voltage can change the lamp's color output, etc., etc.

LabRat
19-May-2017, 00:05
On some of the Durst colorheads, the filters can bind in the movement range... Set the controls to 0 cc and turn on the enlarger cold while just viewing the light while projecting onto a piece of white paper... Rotate the cc knobs for each color, and look for the color to darken as you turn each knob... Flip the filter in/out lever a few times and see if it goes back to the same color setting... Allow the head to get hot, and repeat above... See if there is a full movement of the filters when turned...

If not, how to fix??? Maybe not so easy... You can carefully clean the shafts and sliders with a solvent such as lighter fluid, and re-grease with silicone grease, and check the condition of the nylon gears inside near the lamp (and order a new set or two while you are at it), and push the shafts with your finger (while cold) and note resistance... If bad, you might just push the filters out of the way, and use MG filters as suggested above, or consider a new LED head...

My experience with the CLS heads that heavily used ones develop binding and sticking, and plastic parts inside can crumble, so plan on an upgrade if problems start... Get as many plastic spares as you can for the entire enlarger while you can if you intend to use a used enlarger long term...

Good Luck with it!!!

Steve K

Eric Woodbury
19-May-2017, 12:22
Dichroics are not metal layers. They are related to AR coatings on modern lenses. Not that it matters. They do tend to be very stable with time. Any degradation would appear as flaking, dots, coating-itis. They cannot fade as the color you see is created by interference. That said, filtering LEDs with dichroics is problematic. Depends on the relative spectrums of the LEDs and the filters. Dichroics are so efficient at their filter bands and LED light color is specific to doping (unless the LED is 'white', then the color is regenerated by the phosphor in a more broadband fashion). If the light color and the filters don't line up properly, you will have non-linear behavior from your paper, as far as contrast is concerned. My suggestion, if you want to use the dichroic filter, use the lamp designed for the filters (which is a broad spectrum black-body radiator. If you want to use LEDs, use royal blue and bright green, as these will register the best with the spectral sensitivity of the paper. Then use split printing or variable contrast filters.

Best of luck. EW

bob carnie
19-May-2017, 12:44
Dichroic filters have a metallic coating that is deposited on the glass in a vacuum. There is little or no chance of them fading. However, lamps age, diffusion chambers can become something else then their original color, if it was around smokers that could create color changes over time, if your enlarger is not voltage stabilized then changes in line voltage can change the lamp's color output, etc., etc.

I have to agree with Bob on this, the mixing chambers of some boxes can cause a loss, but I have been printing with Dichroic filters and never experienced a problem.

When using filters for Black and White that is a complete other monster and I am always buying new sets due to handling, heat and scratches.

Bob Salomon
19-May-2017, 13:15
Dichroics are not metal layers. They are related to AR coatings on modern lenses. Not that it matters. They do tend to be very stable with time. Any degradation would appear as flaking, dots, coating-itis. They cannot fade as the color you see is created by interference. That said, filtering LEDs with dichroics is problematic. Depends on the relative spectrums of the LEDs and the filters. Dichroics are so efficient at their filter bands and LED light color is specific to doping (unless the LED is 'white', then the color is regenerated by the phosphor in a more broadband fashion). If the light color and the filters don't line up properly, you will have non-linear behavior from your paper, as far as contrast is concerned. My suggestion, if you want to use the dichroic filter, use the lamp designed for the filters (which is a broad spectrum black-body radiator. If you want to use LEDs, use royal blue and bright green, as these will register the best with the spectral sensitivity of the paper. Then use split printing or variable contrast filters.

Best of luck. EW

Eric, most, if not all, lens coatings are metallic. One of the major benefits of the first coatings were that they made the glass much harder to scratch, since they were metallic.

Eric Woodbury
19-May-2017, 14:05
Bob, not metallic. They have metals in them, sometimes, but what doesn't. Even hydrogen is a metal under some conditions. Metallic implies silvery, malleable, electrically conductive. Coating are things like magnesium fluoride, silicon dioxide, and many other oxides, sulfides, or fluorides. Depends on the base material, but one likes a high and a low index of refraction material to build layered filters. Metallic filters would tend to be neutral density type and not dichroic.

DKtucson
19-May-2017, 15:31
Dichroic filters made from glass do fade over time. I used to manage 1 hour labs and bulbs burning 10 hours a day will fade dichros over say 5 years. Now, you have an enlarger not on constant burn so they will or should last much longer

Sent from my VS985 4G using Tapatalk

Peter De Smidt
19-May-2017, 15:37
Doesn't experience trump theory?

LabRat
19-May-2017, 21:08
But with the filters, they should be evenly colored if good, and not chipped/cracked/broken/blotchy and there... Then you are good to go... I have wrenched on many color heads and only rarely have the dichro filters been bad... So rarely the issue...

And the big one is if the unit is only being used for B/W, you have to come up with your own scale for the different grades... Now, if you were doing color printing, that would be a whole different matter...

Also, the lack of high contrast might be just that some papers don't have a ultra wide MG contrast range (like a paper might only be from grade 1 1/2 to maybe a little over 3 is not uncommon)... Try printing for higher contrast through only a very dark blue filter and see what you get... The paper's contrast layer is blue sensitive, so this will give that layer the max exposure... (Note/ the exposure will be very short...)

Steve K

brucetaylor
19-May-2017, 21:45
I have an ancient Omega color head for my F. I found a plethora of problems inside the well used head after I purchased it, all of which would impact MG printing: the dichroic filters were very dirty, they were misaligned, the internal mechanisms to adjust them were jamming (so the dials read numbers the actual filters never got to) and the mixing chamber had changed color. I strongly strongly suggest you get inside that head and check the integrity of its operation you may be pleasantly surprised that a few hours of cleaning and adjusting will get things back on track.

bob carnie
20-May-2017, 08:31
I never saw and in house technician replace dichroic filters due to fading , but I can ask the fellow who worked on the very same enlargers I have now about this and report back. I was given a couple of the big enlargers Durst 2000 and Devere 515 by them and my friend was with them from the beginning.
Any one know a Durst tech, they would be able to give a very accurate , practical answer as these enlargers are every where.

ic-racer
20-May-2017, 08:46
Mirrors can deteriorate over time. But, if your filter does not look like the mirror below, it is probably still good.
Best test is to sandwich the filter with a step wedge over the paper to avoid stray light of the wrong color affecting the test. Not all "magenta" dichroic filters are the same.
Angle of incidence (AOI) can also influence the results.
https://www.thorlabs.de/images/TabImages/Magenta.jpg

https://s-media-cache-ak0.pinimg.com/736x/be/c8/35/bec835c582e1b50f73ca302dfff468ab.jpg