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Old 29th October 2014, 12:43 PM
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GoodOldNorm GoodOldNorm is offline
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Default Durst AC 707 Autocolour HELP!

Anyone using a Durst AC 707 Autocolour for RA4 colour printing? I have one but I have only used it for black and white. How do you calibrate the enlarger to a colour negative/paper of your own choice?
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Old 29th October 2014, 02:46 PM
marty marty is offline
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Hi, there. Unfortunately I have no experience of this enlarger. A quick peek through the manual reaveals the basic procedure for achieving the built-in color analizer calibration. According to the instructions you should have a reference negative which is supposed to come with the enlarger. I hope this is of some help, waiting for someone more knowledgeable about this machine.

Cheers, M.
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Old 29th October 2014, 04:50 PM
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Quote:
Originally Posted by marty View Post
Hi, there. Unfortunately I have no experience of this enlarger. A quick peek through the manual reaveals the basic procedure for achieving the built-in color analizer calibration. According to the instructions you should have a reference negative which is supposed to come with the enlarger. I hope this is of some help, waiting for someone more knowledgeable about this machine.

Cheers, M.
I have the manual downloaded from darkroom.ru it describes how to calibrate the enlarger for kodak ecktacolor 78 11 rc paper and kodacolor 11 film. I have not got the red reference card giving filter values (the one that fits over the cyan magenta and yellow knobs) or the reference negative. I am in no hurry as I have not purchased any paper or chemicals yet. What I need to know is how to use the exposure/colour analyser. Any help would be much appreciated.
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Old 29th October 2014, 05:50 PM
Mike O'Pray Mike O'Pray is offline
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Norm, this is going to sound a bit numb and vague as I don't have your enlarger but I think that as the paper and film have changed since the Durst was built then I an not sure that the calibration cards and test print will help so I wouldn't worry about not having them. The paper has changed quite a bit as well.

What I think you might need to do is to choose a negative with a good range of colours where no one colour predominates and ideally a neg which includes a neutral grey and flesh tones. The human eye is particularly good at picking out a "wrong" flesh tone and a neutral grey in a print with even a slight colour cast.

Make prints of this neg with your normal paper until you are satisfied that all the colours are as you'd want them. Be prepared to use quite a few sheets.Once you have done this note the Y and M values. You then need to place the diffuser under the lens and with your colour probe adjust the settings in the probe until you have each twin pair of lights for Y,M and C light up.

The probe is now set up to re-produce the "perfect print" Each time you place a negative in the carrier and use the probe and diffuser you alter the Y and M settings until those lights in the probe come on to give you a perfect print of that negative.

If I am right the probe works the same way as the Paterson analyser where you move the Yand M knobs on its probe for the perfect print until the mater nulls. The probe knobs are then left at those settings and each new negative is matched to those settings by altering the knobs on the colour head itself until the meter( in the case of the Paterson) for each colour(Yand M) is nulled. Those settings are the correct ones for the new neg and will produce a correct colour balance for a print from that neg.

I was trying to follow what you do for correct exposure but without the machine in front of me and "playing with it" I wasn't sure but it may be obvious to you.

Not a comprehensive explanation by any means but I hope my theory as to how the probe works with your enlarger matches how it works with the Paterson.

I hope there is some-one here with exactly your set-up

Mike
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Old 29th October 2014, 08:59 PM
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Default I see light at the end of the tunnel

Mike, thank you very much for the detailed answer, what you have said makes more sense than the double dutch in the user guide. I will order some paper and have a go in the near future. My plan is to shoot a test negative as a reference and let my local lab develop it and make an 8x10 print so that I have a finished product to match. I will include a flesh tone, a grey card and some coloured pencils/paints plus something black and white. Can all this be done under a Duka safe light or will it have to be pitch black?

Last edited by GoodOldNorm; 29th October 2014 at 09:13 PM. Reason: added text
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Old 29th October 2014, 10:54 PM
Mike O'Pray Mike O'Pray is offline
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Norm, I think I have managed OK with the DUKA set as low as possible while still being able to see what I am doing. I have mine set at a lower level of lighting than I have set my Ilford safelight for B&W. I say "think" as I have never tried without the DUKA so can't say for certain that I haven't slightly fogged the paper but I think not.

I think you have made a good plan and it will be even better if the paper the lab uses is the same as you will use. Unfortunately when I asked at my lab it's calibration for a print bore no ressemblance to my Durst Head. I couldn't translate the labs digital enlarger settings into quantities of Y and M

I also had a Fuji test negative given to me with a Fuji paper print of said negative but try as I might I couldn't quite replicate the test print and I suspect this might have been because the original Fuji paper used for the test print was not the Fuji paper that is currently for sale. It is also possible that the Fuji negative, called Lucky, was also from a Fuji film that has since been replaced and was quite old so may or may not have deteriorated to add to the problem.

However your plan will take care of all the problems I mention above.

Good luck and let us know how it goes

Mike
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Old 29th October 2014, 11:35 PM
paulc paulc is offline
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Originally Posted by GoodOldNorm View Post
I will order some paper and have a go in the near future.
I have a couple of rolls of Kodak Edge paper (8" wide) sitting in the bottom of the freezer - Send me a note sometime and I'll hack a few lengths off for you to try.
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Old 30th October 2014, 11:21 AM
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Originally Posted by paulc View Post
I have a couple of rolls of Kodak Edge paper (8" wide) sitting in the bottom of the freezer - Send me a note sometime and I'll hack a few lengths off for you to try.
Thank you for the generous offer Paul. I have already ordered some fuji crystal archive which I will pick up next week. I am keen to use the paper with some Kodak porta 400 asa film. I want to get familiar with this combination as it is what is widely available at the moment.
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Old 17th November 2014, 11:59 AM
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Default Update

At last I have had ago at RA4 colour printing. I set the dials on the enlarger to 70m 70y 0c and did a test strip (1/4 sheet of 8x10) to find the correct exposure. Then I dried the print and eyeballed the colour cast, it was to Magenta so I did a test strip +05, +10, +15,and +20 magenta. Yahoo! the +10 looked good. Did a straight print at 80m 70y and my two boys were looking good. Had a play with two more negs and found that without flesh tones in the scene it was harder to judge the colour cast. See attached photos from my fist ever session printing RA4 I am quite pleased with my efforts and with more practice I am sure I will get better. I am using a nova tank and a duka safe light turned away from the printing area, it gives out just enough light to let me see where the slots are on the tank. On the landscape scenes I think the clouds have just a tinge of magenta, but hey not bad for a first go eh?
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Old 17th November 2014, 01:34 PM
alexmuir alexmuir is offline
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Well done! Your prints look good. Where is the scene in the second one? It looks familiar.
Alex
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