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  1. #1

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    REALLY Old Chromega colorhead filters

    Hello,

    I recently acquired an original Chromega D2 enlarger. (Yes, I like old stuff!!!)

    This is the frankenstein-looking one (from 1959-1969) that uses acetate filters, not dichroic.


    Attachment 49198

    The filters are faded and unusable.

    I did find one set (There are two lamps on these heads, so it requires 2 sets) on eBay, the "Yellow Block", so I need the "Red Block".

    Or I need the pair; "White Block" + "Black Block".

    I have talked to Harry Taylor at Classic-Enlargers.com, and he doesn't have any on hand, nor does he remember much about the specifics of these.

    I tried to post in Classifieds/Want to Buy, but it wouldn't let me create a post (Do I have to do something to link my subscription to the forums?)

    So if anybody has experience in either rebuilding the filter packs on these olf Chromegas (There are 2 types...some have graduated 1-piece filters and some use stacked multi-piece filters to obtain the required values), or has a set they would be willing to sell, I'd definately appreciate it. I'd even consider a newer Dichroic "D" head, but would really like to get this cool old machine going again...I like how it looks.

    I'm most likely just going to try to cut up some Kodak Wratten Filters to fit the wheels and repair what I have. I'm just wondering what values to use to match the values on the dials. I don't know if I have to double the filter values because there are two lamps and two filter packs, cut them in half, or add/subtract a certain percentage value, or if it matters that this enlarger uses incandescent vs. halogen lamps in the dichroic enlargers I would use to match the colors?

    Let's say I want to check the value of each color at each 20 units of each color from 20 to 180units...

    Can I just put the same value of filtration in another enlarger, and somehow read it on my little Beseler color analyzer, then get it to match on this big Chromega enlarger? (I have the little Besseler PM1A analyzer, though I have forgotten how to use it)

    Will the intensity of the lamp on a different enlarger (I have a little Chromega B Dichroic or a Meopta 400 dichroic to choose from) vs. this one affect the color readout? Or just the exposure time?

    Interestingly, with these old acetate filters, the YELLOW filters are still in pretty good condition, the MAGENTA are faded, but recognizable as magenta, but the CYAN have lost all semblance of color and are just varying shades of grey. Is this typical of Cyan dyes? Are they more succeptible to fading than yellow or magenta?

    Lots of questions...I certainly appreciate any help anybody can offer, even if it's just a laugh at somebody trying to ressurect a 40+ year-old machine when newer stuff is available...

    Tom

  2. #2
    brucemuir's Avatar
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    You won't get many laughing at your endeavor here.
    I have a DII that I fitted with the more "modern" Super Dichroic D head and I was lucky enough to get all the parts in one place including a few spare lamps.
    The "lifter arm" is different/wider for the color heads and it requires correct spacers. This was the hardest part.

    Anyway, the only thing I can say about your head is I did score a pack of acetate filters that appear to be in decent shape. I got them at the auction site for less then 10 bux usd and included a good selection of densities in cyan, magenta & yellow.
    If you can't find any closer you should PM me and I'll dig them out. I'd let thm go cheap plus shipping.
    I'm in DC.

    I'm thinking you might want to look at the auction site and see whats up. Not to many bid on these and you might get lucky.

    There is a member here named IC Racer that has some Omega experience so hopefully he will show up and give you more definitive answers regarding your specific restoration.

  3. #3

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    The old dyed-acetate filtered Cromega heads are now only practical to use with all the filter settings set to zero and used with below-the-lens filters.

    If you’re intention is variable-contrast black-and-white enlarging, the optically-correct Ilford MG filter kit is excellent and easy to use.

    You can also fashion a filter holder for optically correct CC (color correction) filters for color printing. The filters aren’t made anymore, but can still be found in decent condition on eBay. The optically imperfect CP (color printing filters) can’t be used under the lens because they distort the projection. I’ve only seen a lone dyed acetate cyan filter on eBay for the old Chromega heads in the last 3 years. They are unique in size, shape and the density varied smoothly from zero to maximum density. Trying to find replacements is likely to be frustrating.

    Using below-the-lens CC filters for color printing is possible but is inconvenient and the filters will eventually fade and have to be replaced. If you want to do color printing you’re much better off buying a used Dichro II 404-834 head in good condition with the Standard Power Supply 412-021 and the Voltage Stabilizer 404-841. If you intend on B&W printing only, then the voltage stabilzer is unnecessary. The nice thing about dichroic filters is that they have no color of their own, and so, cannot fade.

  4. #4

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    I guess I don't understand Dichroic...I could swear that my little Chromega-B filters are colored...???

    (Which leads to another question...how narrow is the wavelength passed by dichroic filters? LEDs are available at various Nanometer wavelengths for color...would it be practical to print color with LED lights controlling the color?)

    I'm wondering why would the old Chromega-D be useless for color printing if I repair the filters? Seems like it would then work just like it did 50 years ago?

    I don't plan on using it so much that fading again ought to be a huge issue. This machine was used heavily for many years, and I suspect the fading took quite a long time

    I have plenty of enlargers, so the issue isn't contrast filtering. I have them if I need them on my condenser enlargers (B22 and DII), and I have 3 Dichroic enlargers (Chromega-B, Meopta, and Vivitar VI) that work fine, but I want to fix up the old Chromega-D because I like old machinery.

    I hate to scrap perfectly good machinery, and I think the history of where we've been is important. If this thing puts out the right color, even if the numbers are a bit off (I'll use my analyzer), it seems perfectly servicable to me. I considered the new Chromega-D Dichro head, and may get one if all else fails, but it pretty much spoils the look of this old beast. If I have the same function (I can live with longer exposure time), I'd prefer the old looking machine simply on grounds of aesthetics.

    And, of course, I'd like to be able to print the full frame of my RB67 negatives, (or 4x5 if I decide to go that route) which I can't do on the Meopta or Chromega-B.


    By the way, the filters did not vary smoothly from clear to most dense... They were either overlapping segments of increasing densities stacked on the frame and fastened down, or a single filter with clearly recognizable zones, each subsequent one more dense than the last. I am sure this meant that the stepping wasn't exactly linear as density numbers increased, but because of the angle at which they approach the light path, they should be pretty close.


    Finally, these old enlargers used different size "Mixing Spheres". I have 2 heads for this enlarger, so plenty of parts, but both spheres are the one for 6cmx7cm up to 4"x5" negatives. If anybody has the small 35mm sphere, or the medium 2-1/4" sphere, I would like to buy them if you're selling.


    Tom

  5. #5

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    Dichroic filters are small squares of thin sheet glass. They have a vacuum-deposited metallic coating of no particular color (I think the actual material is somewhat grayish). But when coated onto the glass in a precisely-controlled thickness, the filter works by the phenomenon of Thin-Film Interference to pass certain colors only.

    http://en.wikipedia.org/wiki/Dichroic_filter

    The Chromega Dichroic B color head has dichroic filters as do all dichroic enlarger heads. For example, the cyan filter has a mirror-like surface and looks like it has a reddish coppery color when viewed by reflected light. That is sum of all of the colors it reflects. But look through it towards a light source and you’ll see intense cyan—the sum of all transmitted colors.

    I don’t know the specific wavelength cutoffs for dichroic filters, but I believe that they cutoff fairly sharply.

    I think that the original Chomega heads (1959-1969) used acetate filters made in discrete segments of color. The newer Super Chromega version introduced in 1969 and discontinued in the 1970s used acetate filters with continuous variation of density.

    I found this on the KHB Photographix site:

    “Early Super Chromega heads used the same multi-piece filters as the original Chromega lamphouse. Part way through production, Omega switched to one piece filters and a conversion kit was provided to update the earlier units.”

    The continuously variable ones I saw were one-piece.

    Another comment from the KHB site:

    “The original Chromega heads should be considered as obsolete and we would not recommend their purchase. The filter assemblies have long been discontinued, and while it is possible to replace the individual filters, it is a laborious and expensive undertaking. Nor can the lamphouse be converted to use dichroic filters. At best it could serve as a diffusion light source for B&W printing.”

    If you can get the filters, then you can replace them, but they're now about as common as frog fur.

    There’s a list of the old Omega color heads with some useful comments here. Click onto “Color Heads” here:

    http://www.khbphotografix.com/omega/

    If you could get the filters, then yes, the enlarger would work as new. The problem is that no replacements are available. Could you rig some sort of replacement? I suppose it’s possible, but most of us would find the task impractical, if not impossible. Where could you get such filters in precise increments of cyan, yellow, and magenta?

    If poster #2 can supply you with a complete set the correct filters in good condition, then the enlarger will work like new. I hope that it works.
    Last edited by Ian C; 04-09-2012 at 01:30 PM. Click to view previous post history.

  6. #6

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    Hi,

    I first used a D2 with Chromega head when I was a student in the 1960s and enjoyed using this beautifully engineered enlarger. Some years later, in the early 1990s, I was working at a photographic college that also had a Omega D2 enlarger with Chromega head, that was used for C-type printing. The colour head filters had faded but the college couldn't afford new kit at the time and we had to make do. Making colour prints required a certain knack, as at one point on the yellow scale a 15 or 20 alteration needed to be dialled in to make a 05 change!

    Eventually the college had the money to replace all its 5x4 enlargers with new De Vere 504s and I was able to buy the Omega enlarger for a nominal sum.

    I have always enjoyed a bit of DIY with photo equipment (I have an Olympus XA in pieces at the moment), and I overhauled the Omega. When I stripped the Chromega head I found that the filters were the earlier type, with six stepped segments, each segment being 30 degrees. The cyan filter was unfaded – only the yellow and magenta filters were used with the C-type printing that the enlarger had been used for. I used the college densitometer to check the densities of each cyan segment. The densities of the segments were 0.21, 0.47, 0.85, 1.25, 1.60, 1.77

    I also checked the densities of different filter sets – I had Kodak acetate and polyester CP filters, and a couple of sets of Cibachrome polyester filters. (Cibachrome were close to Kodak, but they all varied from the stated density by up to 20%)

    I decided to make a sandwich of filters to get close to the original densities. A Cibachrome segment sandwich was as follows (using the original filter as a template):–
    2 pieces 180 degrees of 10 filter
    1 piece 150degrees of 20 filter
    1 piece 150 degrees of 05 filter
    1 piece 120 degrees of 40 filter
    1 piece 90 degrees of 40 filter
    1 piece 60 degrees of 30 filter
    1 piece 60 degrees of 05 filter
    1 piece 30 degrees of 20 filter

    The overhaul was very successful and over the following years I printed many C-types and B/W prints. The D2 is still in use today as my only enlarger for 5x4, 6x6 and 35mm., although now only used for B/W printing. I really enjoy using what is a great piece of kit. I have recently thought about looking for a later dicroic head but the Chromega head works well and so see no need to change.

    Graham Morley

  7. #7

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    Until about 6 months ago I was using the old Chromega "space-head" mounted on a D2V chasis in my darkroom. Right now it's in storage, but I may go back to using it again at some point. Just to have some spare parts I picked up another spare space-head on Ebay. I've never used it, and indeed it's missing the plug, plus I've scrounged a couple screws, etc. from it to use on my working space-head. I think I still have the spare head tucked away, unless I threw it out in a fit of housecleaning. I'll look tonight. If I still have it I'll give you a good price on it.



 

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