Colorhead settings change as height changes

[Ian Grant]

A friend runs a pro-lab near where I live in the UK, he spent many years as a Durst engineer and he taught me many years ago that to overcome slight colour shifts at different enlargements adjust the aperture to keep the actual exposure time constant. All his printers were adjusted so that the exposure was constant regardless of the lens used, and they did the same with their LF enlargers.

Using this constant exposure time method means that any warm up and after glow is constant, and with older papers helped overcome reciprocity too.

Ian

 

[Photo Engineer]

What Ian says is what I also do (or try to do) but sometimes due to magnification I just cannot do it, I have to change exposure time. But, within those limits, color balance is unchanged as is filter pack.

However, there have been many reports of recent deviation in Fuji CA filter packs. I have to assume this is their new CA II paper which uses new emulsions. It was reported on at the ICIS conference in 2006 here in Rochester. Apparently, the filter pack change is not trivial.

PE

 

[Michael W]

I heard the paper changes were to optimise for digital printing, i.e. lambda & frontier but the paper is now more difficult for optical printing.

 

[Photo Engineer]

I heard the paper changes were to optimise for digital printing, i.e. lambda & frontier but the paper is now more difficult for optical printing.

Not so!

The changes made it all round better.

PE

 

[FilmIs4Ever]

Even without afterglow, which most people do have to deal with so it will factor in, you're going to run into paper reciprocity.

A good rule of thumb is to adjust F/stop rather than exposure time, but this will then start to affect sharpness at either extreme of the lens.

I'd say that you'll run into paper reciprocity shorter than 10 seconds and longer than about 60, it'll be minimal within this range.

With B&W paper, I've heard you still get about 1/6 stop of reciprocity every time you double exposure. It will be different with color paper, but probably not too different.

Kodak and Fuji papers have gotten much better than other competitors' (are there any even left?) in terms of minimizing color shift with changing exposure, but IT IS STILL THERE. If anyone would like, I'll post samples. I was using "Ultrafine" paper back in '05, probably rebranded Mitsubishi or Konica or Agfa, and it had very pronounced color shifts with changing times.

The newer papers have probably been heavily optimized for short exposures; there'll be little to no improvements over a minute, as they're working on optimizing paper for quicker exposure in digital machines, and really couldn't care less about people dodging and burning in the color darkroom. If Kodak cares so much about color darkrooming, then why did they discontinue the 5x7 size?

 

[Mick Fagan]

The shortest time I usually expose colour paper for is 2 seconds, under that I have repeatability problems, which is due to the warmup and warmdown times of my single 250 watt globe light source.

Having visited the retail colour printing kodak lab in Melbourne, I saw the film, which was in 1,000 foot rolls, being exposed by a computer controlled system. Let me say that the machine(s) sounded like machine guns, the rapid firing of their flashes was something you had to hear. These machines were in the eighties and were running the now discontinued EP2 colour paper process.

When photocopying, we sometimes used 8x10 colour negative film. Using a Durst 8x10 enlarger with a shutter blind, it was not uncommon to use an exposure anywhere from 1.5 seconds through to a minute or more. depending whether you were enlarging or unlarging, as we use to call it. Never, did we have any reciprocity problems that I'm aware of, using this enlarger.

However if we used another enlarger without the in-head shutter, extremely short times were problematic.

With the release of the RA4 paper and process, things just got better. I assume the very latest paper from Kodak, which I haven't used yet, will or should be better, not worse.

When going from one enlargement to another with colour, I pull the neg holder half out, and take a reading of the light strength, using either my EM10 meter or my Colorstar. I then re-compose after height adjustment, then repeat the pull the neg carrier half out bit, then take another reading. With the EM10 I always adjust the aperture, with the colorstar, I always adjust the time. The results with either instrument are indistinguishable.

Mick.

 

[Richard Harris]

lively thread this one, I have posted on this and other sites regarding this colour balance thing. I use a colorline 5000 and find it's my best friend, but not always true to me! I try to use a constant 10 to 12 seconds exposure, this requires lots of neutral density filtration for smaller prints and I am using a single halogen 100w bulb in an LPL 6700. I am convinced that lamp temperature is the key here and I find my filtration settings vary from print to print wildly. I have monitored the power supply voltage and I don't get more than 3 to 4 volts change accross a 240 volt supply. That is less than a stabalized voltage supply yet still my filtration is all over the place. It seems that we all have to learn to disagree about this and use our own methods. Ron who must be about the most respected member of this forum insists that filtration values have changed little for years and that prints can be made using the same settings 10 or 20 years ago. All I can say is I wouldn't even think of using the settings I used yesterday without confirming with the colorline and even then for an important print I would make a slight adjustment. What I think would make the difference is a shuttered head but that is out of my reach, price wise. Hey ho!

 

[FilmIs4Ever]

However if we used another enlarger without the in-head shutter, extremely short times were problematic.

Right. The whole point is that no one except lab owners own machines that have built-in shutters.


I have a Lucht that has an exposure shutter, but these machines retail(ed?) for $20,000, USED.

I wouldn't go below 5 seconds with an *enlarger* without expecting and compensating for reciprocity.

I wouldn't go over a minute regardless of equipment used without compensating for reciprocity.

 

[stevewillard]

This is a excellent discussion here, and I will be printing this out, studying it, and using it to formulate strategies for improving my efficiencies in print making in the darkroom. Here is the direction I am moving in.

1. I have invested heavily in mask technology and have invented new methods for masking. Once the mask a are constructed then it becomes a simple single exposure to make a print with no dodging and burning. This will greatly reduce the complexity of print making and allow me to hire a less skilled printer to do my printing. It will also increase the productivity in the darkroom allow me or my printer print more prints in a day. The registration pins for my mask in my negative drawer are a 1.25" high, ranging from five to ten layers of mask for a negative, and some layers can be 3/8" thick.

2. Develop methods that allow me to more finely control the variables in printing and reduce the number of test prints needed to make prints that exactly matches my 8x10 mater print. The variables I know of are aging of lamps causing color temperature changes, paper chemical variations, differences between batches of paper, changes in settings do to colorhead height, and exposure times. If there are any other variables I have missed please let me know.

3. Keep accurate database records about each image. This will allow the printer to quickly reference the image and set up the enlarger in a timely manner.

 

[Nick Zentena]

Your colorline should be able to handle everything in #2. If it's like the colorstar it's got a mode to adjust for chemical drifts. You just make a new grey test strip then hit a key or two.

 

[stevewillard]

Nick, I suspect that you are right. I was actually thinking of selling my JOBO 7000 analyzer, but I am glad I did not. I think it will prove to be extremely helpful tool with item two in managing all those variables. I do use control strips to monitor and manage my chemistry with my roller transport, but the analyzer will allow me to manage all those variables at system level in a concurrent fashion.

 

[Photo Engineer]

Interestingly enough, I have a 50 year old negative of my mother and a recent photo of the family that both print at just about the same color balance (within about 10 Y as I said before), but when I used my color analyzer(s) (- I have 2) the color analyzer suggested a totally different filter pack for the old negative but agreed with several recent negatives that the color pack I was using was correct.

I printed the old neg at the analyzer suggested pack and the picture was awful, so I went back to my standard and sure enough it was about 10 Y off. The other one, suggested by the analyzer, was deep orange and almost black.

I had flesh tones in both cases to zero in on.

I find a color analyzer to sometimes get very confused, especially with old or unmasked negatives or those from the Kodacolor CU film days. I've actually quit using them and go on eyeballing my negs now.

One final note. I finished printng new proof sheets on Endura about 1 year ago and have over 1000 sheets of 8x10 proofs of 4x5, 6x7, 645, 120, and 35mm. In fact, it is probably closer to 2000 sheets as I gave up counting. I was doing 48 sheets / night for a while. I used the same filter pack on all of them and they now fill over 16 notebooks.

So, I have begun sharing this fact with visitors. Some of you have seen my old and new proofs with the same constant exposure. I use my enlarger set at a fixed height with a lens set to focus on an area that would make an 8x10 from a 4x5 with 1" margins. The enlarger is set at 12" and a constant f stop and filter pack. I have a complete description of this in my first notebook.

These were all at 100 F (38 C) using a Jobo.

On the last few sheets, I began converting over to 68 deg F processing and saw a tiny shift in color balance.

My last project before the emulsion work was making internegatives from my slides using a pack in the enlarger that gave me the same general printing filter pack. It was 100 C and 30 M. I am therefore able to make locked pack prints on all of my negatives and internegatives and be within a hair of the right value.

PE

 

[Nick Zentena]

The colorstars and I guess colorlines are programmed by making a grey print. Sort of like printing your own grey card.

I use it in spot mode and more or less carefully select the spots to measure. If I do a reasonable job selecting the eight points to measure it does a fairly good job.

It can get fooled but in my use going back and being more careful in picking the points solved the problem.

I wouldn't use it in combined mode with the diffuser over the probe. I just never got comfortable with that.

 

[stevewillard]

Very interesting PE. Perhaps this fall I need to give Endura a try. Its variation from batch to batch might be much less than Fuji CA.

I have a Fujimoto CP-51 and running at 68 deg F for RA-4 seems more appealing to me because the lower temperatures will slow oxidation, evaporation, keep odors down which my wife complains about, and keep my darkroom cooler. I can live with adding one minute to the development times to compensate for the the lower temperature. However, I am a little concerned about the washing of the print. People have told me proper washing is very important to image stability. Is it possible to process the prints and 68 deg F and still continue to wash the prints at 100 deg F or even higher temperatures? I have a wash/dry unit on my machine and can set water temperature independent of the main processing unit.

I do not intend to use the analyzer as a predictor for color settings for each print. The colorline has the ability to produce a "pure virtual gray" paper that is iterative. I have never used it before. Roughly you expose a small sheet of paper with all three colorhead settings the same (I think) and the process the paper. Once the paper is dry you then place the paper directly over the over the sensor, and the sensor will light up the paper and will measure the gray. If the gray color is "correct" then you are done, otherwise it recommends another set of corrections to the colorhead to get closer to the virtual gray and you process the paper with the new correction and test the gray again. This process it repeated until no corrections are needed. Once this is done for a batch of paper then you can record the difference between some arbitrary master settings and corrections needed for this batch of paper. All my colorhead settings recorded in my database will be in master settings for each print, and then I add the batch paper corrections when I go to print. If a batch of paper has zero corrections then it matches the master settings and no corrections are needed.

Of course, if there is very little difference from batch to batch then this is not needed. However, using this master setting approach that never changes, I can use any paper I choose independent of manufacture or paper type. I simply compute the the batch setting corrections for each paper such Endura, Fuji CA, Fujiflex CA or any other color paper and add them to my master settings I have recorded for each print. As papers come and go or new versions are introduced, I can simply compute new batch corrections to get a correct gray for that particular paper batch. This would allow me match very closely my master prints on a first try independent of manufacture or paper type. I also believe the analyzer not only provides colorhead corrects for each batch, but also exposer times/ print densities for each batch as well based on achieving a "correct gray".

I think this approach would provide me with the greatest flexibility given the instability of the industry.

 

[Photo Engineer]

You can wash at 85 degrees after a 68 degree process. Use about 10 minutes at 85 degrees. I hold my prints at 75 degrees in a still water bath until an evening session is finished, and then ramp the temp to 85 with running water. This does not reticulate the paper. I then interleave a deep tray of prints for the 10 minutes and set them out to dry.

The current reports I have say that Endura had two shifts in color balance. They were both clearly printed on the box. The first was the change from Supra III to Endura, and the second was about 1 year into Endura production. Within those two populations (the second of which continues to the present AFAIK), the papers have been more stable than Fuji CA. There appear to be 3 or more populations of CA out there. You may want to search on these problems with CA color balance. Some have actually resulted in cyan filter packs which is very unusual and can lead to color contamination.

PE

 

[Thomas Wilson]

Density B/4 color correction

Has anyone notice if you change the height of the colorhead then you have to change the YMC settings to compensate for a change in the color temperature of the light source? The changes are not large, but they are needed.

To be honest, no. I have not noticed a change in color when adjusting head position. I do notice that an increase in exposure time is needed to maintain the density of the print as the head is raised. The first rule I learned 20 years ago working in a custom lab was to nail the density first, then adjust for color.