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CHROMEGA D4 FILTER VALUES?

Philippe-Georges

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I dug up my old Chromega D4 again because I had a series of rather 'harsh' negatives that perhaps would be better printed on a diffuser head enlarger.
But I never printed FOMABROM FB III with it, only AGFA, and I know that the dial in filters concur with the KODAK colour printing filters from that time.
The tech. data from FOMA only speaks about the DURST values for a colour enlarger and ILFORD Multigrade filters for B&W, but no KODAK information.
I would like to know how to convey KODAK <—> ILFORD filter values.
So, I can make a chart with the contrast values in ½ steps as a starting point, and variate afterwards.
 
I recommend that you look up Tim Hall on YouTube. He has a few videos showing detailed filtration calibration for both Ilford and Foma current VC papers, including selenium toning, all using an Omega dichroic head.
 
Unless it is the later dichroic head, that head "utilized acetate filters in a "wheel" arrangement to provide stepless filtration."
 
MattKing said:
This page from the Ilford publication "Contrast Control for Ilford Multigrade pdf - which can be found here - https://www.ilfordphoto.com/amfile/file/download/file/1824/product/2019/- may supply you with your "Rosetta Stone"
View attachment 336851
Click to expand...

Thank you very much Matt!

That's what I need, it didn't occur to me to look into the ILFORD documentation to find info that could apply for FOMA...
But thank you again!

I think I will use the dual filtration, as I did at the time with the AGFA paper.

The Chromaga I have is the old one, the so called "Mikey Mouse", using these impossible to find longish bayonet bulbs at 20V in pair.
I still have a few in spare, but when one dies I have to change both to be sure that the lightening will be evenly as these bulbs are blackening with age.
But I keep the still 'good' one, so I have two 'old' bulbs when the the other one dies too...
 
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aparat said:
I recommend that you look up Tim Hall on YouTube. He has a few videos showing detailed filtration calibration for both Ilford and Foma current VC papers, including selenium toning, all using an Omega dichroic head.
Click to expand...

Thank you very much Aparat,

But, the only Tim Hall I could find on YouTube is a very annoying pastor preaching "Global Evangelism" and linking the Ukraine war with the bible's prophesy (which I didn't understand at all)...

If you do not mind, would you please sent ma a link, as this filtration calibration can be interesting.
 
No problem. It starts here:

and continues for a few more episodes. Some of the more "juicy" information is sometimes buried in the middle of the video, but it's well worth watching, especially if you are interested in printing by numbers and figuring out filtration for the current Foma and Ilford papers.
 
One problem trying to rectify different calibration systems using charts etc is that older colorhead filters themselves tend to be off from their original values. Dichroic filters do not fade per se, but over time or with excessive heat might spall off a significant percent of their original coating, allowing more unfiltered "white" light to pass through. Older filters also tend to accumulate a fair amount of grime (extreme care must be used if attempting to clean them - those old coatings can be quite fragile).
 

Yes Drew, you are right.
That's why, at the time of printing on AGFA paper, I added an M40 filter (actually two one on each side) just to compensate for the fading of the built-in dichroic filters.
The value of M40 was found by trial and error and it worked.
Now I will have to find out if this added M40 will do for FOMA too.

I have seen on the internet in the US a set of new filters for the Chromega, but buying outside the EEC is absurdly expensive partly due to shipping but even more due to import taxes which would triple the price...
 

Thank's Aparat, this is a completely different thing than "biblical prophesies and –warfare"...
The numbers are, for me, just a kind of handhold, then I variate.
 
The gel filters in those old Chromega heads fade with use. A long time ago, on the job we had a Chromega enlarger alongside the newer Super-Chromega dichroics. The Chromega required much higher levels of filtration (to print color) than the Supers. I hadn't been around long enough to notice the change in filtration numbers over time; this was explained to me by the old-timers in my group. Then they gave my group a budget increase and the old Chromega was replaced... must have been around 1988.
 

Making a multigrade calibration table for color head

I got a bunch of Forte multigrade paper on sale at the local shop. Here is how I calibrated my color head to allow me to keep the same middle gray exposure while changing contrast grades with the color head. It involves adding in RED to the Magenta or Yellow filtration as neutral density, so...
www.photrio.com
 
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