Computer Aided Colour Printing

Berri · Nov 6, 2018

I have been thinking about a software capable of simulating the effect of filter settings on the enlarger head. It would need to be some how calibrated, but I think it would be possible.
In the old days there were automatic machines for printing which used a monitor to preview the results.
Do you think such a workflow would be possible/useful?

Mainecoonmaniac · Nov 6, 2018

I don't know if your effort will pay off. I've used a Professional Video Analyzing Computer (PVAC) when I worked at a color lab. I think it's an analog system. The machine is made for high volume labs. There was a special color head that went with the analyzer. But for it to work, the print processor has to be maintained for consistant color and the analyzer has to be calibrated from control strips which you have to run daily. I never got competant on the computer and it was more trouble than it was worth for me. Take a look.
http://www.photolabstuff.com/pvac.htm

Berri · Nov 6, 2018

Mainecoonmaniac said:
I don't know if your effort will pay off. I've used a Professional Video Analyzing Computer (PVAC) when I worked at a color lab. I think it's an analog system. The machine is made for high volume labs. There was a special color head that went with the analyzer. But for it to work, the print processor has to be maintained for consistant color and the analyzer has to be calibrated from control strips which you have to run daily. I never got competant on the computer and it was more trouble than it was worth for me. Take a look.
http://www.photolabstuff.com/pvac.htm

Yes I think it might be not worth doing it, but the idea of being able to preview the negative and translate it into paper directly is always on my mind.

Chan Tran · Nov 6, 2018

Berri said:
I have been thinking about a software capable of simulating the effect of filter settings on the enlarger head. It would need to be some how calibrated, but I think it would be possible.
In the old days there were automatic machines for printing which used a monitor to preview the results.
Do you think such a workflow would be possible/useful?

I did for printing color negative on RA-4. I use a film scanner. I scanned the film using manual settings. Manipulate the scanner controls (exposure, R, G, B) until I get the image I want on the computer. Translate those settings into exposure time and filter settings on the enlarger. To ensure consistent result I modify a Minolta/Sargent Welch color analyser to measure the output of the enlarger ( after the diffuser but above the negative.). It works OK for me though.

RPC · Nov 6, 2018

Mainecoonmaniac said:
I don't know if your effort will pay off. I've used a Professional Video Analyzing Computer (PVAC) when I worked at a color lab. I think it's an analog system. The machine is made for high volume labs. There was a special color head that went with the analyzer. But for it to work, the print processor has to be maintained for consistant color and the analyzer has to be calibrated from control strips which you have to run daily. I never got competant on the computer and it was more trouble than it was worth for me. Take a look.
http://www.photolabstuff.com/pvac.htm

Did your machine require different settings/programs for different film types?

Bob Carnie · Nov 6, 2018

RPC said:
Did your machine require different settings/programs for different film types?

I used this machine with master shirley negs that we calibrated for normal, under and over slopes... each day the VCNA was balanced in, then one needed to balance in your translater to it, then you would use the machine to colour correct your negatives against the master shirley.. the difference was recorded and you applied this difference into your translator and with probe at enlarger height at the easel one would adjust the yellow and magenta filter along with the apeture scale and record this new setting and make your test print. I was very good at this and the test prints were within a few points Max of colour and within great density range.

I would only bite off as many negatives a day as I felt was possible and the next day the same calibration was required( took about an hour out of a day but was well worth)
I do not see any way to replicate this today, the VCNA was the price of a house and extremely sophisticated Kodak system.

Mainecoonmaniac · Nov 6, 2018

RPC said:
Did your machine require different settings/programs for different film types?

I don't remember because it's been over 20 years. I do remember the 3 color wheels and a wheel to adjust for the density of the negative. Once I think I got a print that is correct on the screen, I would write down the numbers then transfer the numbers to the color head for exposure of the RA color paper.

MattKing · Nov 6, 2018

Bob Carnie said:
I do not see any way to replicate this today, the VCNA was the price of a house and extremely sophisticated Kodak system.

The possibility exists that a system like this might actually be cheaper to implement today - a lot of work has been done since then with respect to software/firmware image manipulation systems and computer controls.
However, the real challenge would be whether there is a viable market for this.

ic-racer · Nov 6, 2018

I have a 'translator' for my Omega D5500 color head. It was intended to 'translate' the values from a VCNA so one can make a color print that matches the color on the VCNA screen. I don't use that function; I only print B&W. Post #2 by Mainecoonmaniac probably sums it up best, though, it may not be expensive to try it for yourself (see ebay ad below).

Berri · Nov 6, 2018

Chan Tran said:
I did for printing color negative on RA-4. I use a film scanner. I scanned the film using manual settings. Manipulate the scanner controls (exposure, R, G, B) until I get the image I want on the computer. Translate those settings into exposure time and filter settings on the enlarger. To ensure consistent result I modify a Minolta/Sargent Welch color analyser to measure the output of the enlarger ( after the diffuser but above the negative.). It works OK for me though.

Interesting. Can you give more details about your workflow?

AgX · Nov 7, 2018

Another way to tackle this would be to use one of the Philips Tri-One enlargers. They employ additive filtration by intensity control. Thus can be used as any standard enlarger. The analyzer is directly coupled to the colour head, for automatic filtration.

This is not at all what is described above and done in industrial printing, but it gives you automatisation, in case this is what you are after.

EdSawyer · Nov 7, 2018

The Minolta/Beseler 45A color head (Additive RGB) has a nice analyzer and metering probe built into it. Granted it's not interfaced to a computer but it makes nailing a print pretty easy and can support multiple programming channels for different film types, lighting situations, papers, etc.

ic-racer · Nov 7, 2018

AgX said:
Another way to tackle this would be to use one of the Philips Tri-One enlargers. They employ additive filtration by intensity control. Thus can be used as any standard enlarger. The analyzer is directly coupled to the colour head, for automatic filtration.

This is not at all what is described above and done in industrial printing, but it gives you automatisation, in case this is what you are after.

Actually the D5500 has an integrated analyzer function, in addition to the VCNA translating function. The Philips Tri-one does not have an integrated analyzer or a means to interact with a VCNA. It is more primitive than the D5500, in that the light intensities are controlled by rheostats, rather than the computerized feedback-loop that controls the filters of the D5500. The advantage of the VCNA is that you can actually see the color changes on the screen before you make the print. Using a probe on the baseboard does not have the same advantage.

DREW WILEY · Nov 8, 2018

All kinds of options were out there, like the Jobo Colorstar. If any Kodak video analyzers still exist the maintenance backup would of course itself be long gone, and you might need to find multiples just for sake of replacement parts. A lot of fuss for nothing, unless you're a mass-production lab. A simple test strip is nearly as fast, and more accurate. Many pro color printers could get close to a bullseye simply with a color transmission densitometer reading of a color neg, provided it was a familiar subject like portraiture or a gray card in the scene.

DREW WILEY · Nov 8, 2018

Let me again point out that the old Phillips tricolor enlarger was extremely weak and relied on simple rheostats to lower the voltage of a bulb with respect to another. This means that one primary color (most likely blue) might fall into reciprocity failure while the other two did not. Just one of the potential headaches.

Berri · Nov 8, 2018

ic-racer said:
Actually the D5500 has an integrated analyzer function, in addition to the VCNA translating function. The Philips Tri-one does not have an integrated analyzer or a means to interact with a VCNA. It is more primitive than the D5500, in that the light intensities are controlled by rheostats, rather than the computerized feedback-loop that controls the filters of the D5500. The advantage of the VCNA is that you can actually see the color changes on the screen before you make the print. Using a probe on the baseboard does not have the same advantage.

I just bought a D5500 with the CLS head but I haven't had the chance of using it yet. I am used to my Colorstar 2000 wichw gives me quite good results. How does the d5500 work compared to the Colorstar?
Could it be possible to somehow use a device like the tamron fotovix to preview the negatives and translate the values from fotovix to the enlarger? Maybe not...

Computer Aided Colour Printing

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