There is a thread going on right now about Deveere dichroic filter fading that could shed some light on the topic we are discussing here.
Originally Posted by Bob Carnie
I worked with color papers intensely for over 50 years, and am aware of what all you say. I started to work with them at the time of the Consent Decree in the 50s.
When I found this constancy, I was surprised by it myself.
To explain how I found this out, when I retired from EK, I had just inherited all of the family color negatives taken over a span of over 50 years plus my own.
As a project, I took on the printing of contact sheets of all of these and it took me a complete fall and over 1000 sheets of Endura paper. I ran about 24 sheets / night. Through it all, I used one filter pack, one exposure time and fstop and made those 1000+ contact sheets of negatives.
All of them are within that 10R but vary in exposure (density) in the old cameras more than new cameras, and the only ones that lie outside of that range were taken on the old CU Kodacolor film in the 50s-60s. It was balanced half way between tungsten and daylight if you remember.
So, if you ever come to Rochester, I will happily show you about 10 thick notebooks with 100 sheets each of proof prints, and I will show you my notebook with all of the data recorded in it. That filter pack has been my center point and works as well from a 68 degree tray process to a 100 degree Jobo process. I'll even buy you lunch if you can show me my 'operator error'. And, if you show it to me, I'll publish it right here!
If my darkroom is clear of the emulsion making stuff, I will even be happy to make a print for you or let you make it yourself.
Now, I must admit that this would not have worked 50 years ago. Color paper varied from batch to batch too much, but not the film. And, there were 2 bumps in the road going from Supra III to Endura (type I) and Endura (type II). There were 3 filter packs involved with small changes in filtration that amounted to being within the 10 red, but moving me from one end of the range to the other. Within those 3 types of paper though, the filter packs stayed constant. I'll show you those small changes as well.
I made prints at one filter pack, then a 'corrected pack as noted on the box' and put them both into the folders when I crossed over papers. So, I not only have the locked beam prints, but the 'corrected' prints as noted by the manufacturer due to changes in the paper.
Thanks all for the replies. Yes the bulb is low wattage(75W) but is relatively new and didn't cause problems with low/non existent Y filtration before. It was changed from 100W because exposures with the 100W were too short to register on the analyser which only goes as low as 4.5 secs.
However I will try a process of elimination by changing back to 100W and also changing the bulb for the new spare as well to see what effect this has on filtration using the same negs. I can add ND by dialling in C if necessary.
The M filtration remains about the same as before but presumably a non problem with the M filter on the dichroic head does not eliminate a problem with the Y filter. How do you tell for certain if the dichroic head is worn and can it be cleaned or the filters be replaced? It's a Durst 605M Color. I always thought that a dichroic head lasts virtually forever. The enlarger is secondhand and probably the best part of 20 years old but I know the previous owner and that it sat unused for a good portion of that time.Also if the last time I used the head the Y filtration was OK, then I wouldn't have thought that the deterioration could be that sudden. I would have expected a gradual deterioration.
Both sets of negs look OK except that the Fuji 100 negs look "thicker" and this is borne out by the fact that these negs need greater exposures which are within the analyser's range whereas the Fuji 400 negs need the 6X6 light box to be switched in. I can't explain this except to say that my wife's Olympus compact's automatic exposure in terms of light may be different from my Pentax so it overexposes relative to my Pentax or the latter underexposes but I can't see how this accounts for the filtration problem. The scenes shot and light conditions were virtually identical.
So I have one set of negs which are OK exposure-wise but some of which have a blue cast I cannot eliminate and another set which are OK(just) filtration-wise but most of which need the 6x6 box as opposed to the 35mm box to get exposure into the range for which the analyser is calibrated. Now if only I could combine the two....
Bob. You mentioned switching to C and M as the equally acceptable alternative to Y and M( and yes I also noted your reservations PE) but you didn't say if it was possible to convert the correct Y and M values on the head for the test neg to a C and M values on the head to at least get close to the same colour balance on the test print. I have never used C before for test prints so was hoping to get close to the correct values to avoid wasting paper and time.
I should have added that I opened my second box of Fuji and found no difference so I agree that unless I have two boxes of faulty paper then the odds are against it being a paper problem unless somebody or bodies reply that they have experienced the same problem.
Anyway there's more food for thought in all of your replies. I'll keep plugging away and let you know what the process of elimination produces.
Once again thanks to all of you
A CC10M and CC10Y = CC10R To negate that or equal it, use a CC10C and if you need to move by 20R then removing 10M and 10Y and adding 10C gives you a 20C (removing the 10R = 10C and then adding 10C so you have 10C + 10C.
Always remember thought that a 10R is 'purer' than a 10R made from a 10Y and a 10M due to the dye absorptions and interfaces between the sheets of filter material. This adds just a touch of neutral density.
R = M + Y = - C
G = C + Y = - M
B = M + C = - Y
Our printing experiences differ.
Maybe I am not reading in to what you are saying.
Are you suggesting that 50 years of colour negatives from different source materials have resulted in a printing session of 1000 sheets of colour paper and the filter pack in the enlarging head did not change more than 10red?
If so you have discovered the holy grail! and should be honoured .
I am not sure if my clients would accept me printing with only a 10red palette.
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Bob, I am saying exactly that and am willing to share the results with you if you are ever in Rochester. You see, negative film from EK is made to the same exacting standards for speed as are the reversal films, so this is possible.
It was not possible before the introduction of the fixed speed color papers back in the 70s, and there was a bump in the road when Endura was introduced, but otherwise, this is what I found and the notebooks are sitting right here.
Not only that, but I process from 68 deg F to 100 deg F with little change in exposure as well.