Thanks, that makes the process very clear. The vast majority of my successful efforts have been in analogue black & white where one can guess a good starting exposure and contrast grade...
Thinking through the process of using the Expo/Disc it would seem that using a through the lens metering camera would be helpful, rather than placing the Expo/Disc over an external light meter.
It doesn't matter what you use as a grey negative you just need to measure an area and make that area grey when you print. I would suggest you photograph a white towel and fill the frame with it You will then have a negative with a total area of uniform colour and a textured surface to measure exposure. You could use a red towel, it would make no difference. You are setting the analyser to print a grey tone, not measuring the colour of the negative. Personaly I find skin tones and grass colour etc just as important as finding a grey So I use spot metering of these areas projected on the baseboard of the enlarger. Most negatives will not integrate to a perfect grey and so using integrated measurements is less use than using your normal filtration and adjusting the results, IMHO.
If you read what Mick has said carefully, his method suggests although I don't think he said it directly, or maybe he did, you make one grey negative to give your initial calibration of the colorstar and then for each subject in different lighting, you make another grey negative. Using that grey negative from each subject to set your filter pack for printing but not actually printing it, automatically corrects, near as damn it, for the colour temperature of each individual subject. That should save a lot of paper when printing as with a little experience, you should only need to make one density test for each print and it will be nailed for time and colour.
flogging the horse named colorstar 3000
boy - what a discussion, and this is a device that makes color printing so much easier.
The colorstar has either 8 or 99 channels, depending on its firmware. Mine has 8, so I keep a log of the numbers for way out there channel readings and dial the numbers to match the recorded settings into channel 7 or 8 when I need them. Things like blue sky, green grass, white clouds.
Most of the time I use grey from a betty neg I made up to calibrate the system at the beginning of the session. Ths neg is even taped to its own matt board neg carrier. Channel 1 for ng, meter, dial the filters, aperture to be near 5s, and expose, process, hair dry, autocalibrate, and away we go, dialled in for the night. Chanel 2 I have set for spot neutral caucasian flesh, and channel 3 for spot, warm caucasian flesh. These 3 use 90% of the time.
With the flesh channels, the need for me to shoot a grey each roll is almost never needed. Usually there is a snippet of flesh somewhere on the roll, or on another roll that I shot that day, so that the second print is bang on, if the first print is a bit off.
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Sure is a lively thread!
But, The colorstar is measuring the light output of the negative and if you zero the filtration to a setting that has given grey or any other colour before you will get grey or that colour again. You do not need to have a grey neg for different light or even a grey neg. You are measuring the light to produce a colour on the print, you are not measuring the negative. Grey is the easiest because most analysers will measure the print and knowing that grey is equal quantities of all the primary colours, can, after measuring the light transmission through the print, suggest a filtration change to get closer to it. Repeat this has nothing to do with the colour of the negative. As long as you measure the same point, easier with a negative of uniform colour accross the entire frame, you can produce a grey or any other colour and record the light needed to produce it.
I use the jobo colorline which is very similar and has the same features. The only real variable is process changes like chemical exhaustion, the analyser can't deal with these until recalibrated the colorline stores these changes on a master channel so it changes the calibration for all your channels set up for the same process. I am sure the colorstar analysers have the same features.
Incidently, Mick's idea about using an expo disc to measure the light temperature is a different thing to calibrating your analyser to grey. It sounds like an interesting idea though, but Mick, what happens if you have taken your expo disc exposure pointing at a red car? using this to grey your enlarger will surely result in nothing but a green cast on your print. Tell us more Mick....
I did say read what he said CAREFULLY! I think you are missing something. Listen carefully now...
Originally Posted by Richard Harris
First you make one grey neg on a nice sunny day so the colour temp is fairly neutral. Doesn't matter if colour temp is slightly blue or slighty red or slightly green. You just go ahead and print it until its pure grey on the paper.
So it might have a bias towards blue or red or green but it will be minimal if done on a nice sunny day. That is what you calibrate your colorstar to.
Now when you make another grey neg when photographing a subject, the colour temp may be slightly red or blue or green or any other colour. Doesn't matter. Why? Because when you set the colour pack using that subject grey neg, you correct for the colour temp in the subject against your calibrated standard reference. Doesn't matter that the standard calibrated reference is not a pure grey because it still prints as a pure grey.
p.s. you are not using the subject grey neg to calibrate the colorstar, you are using it to set the colour pack for printing that negative and its variance will adjusted to match the calibration grey neg.
First, let me assure you that you are free to do anything you want to do. I can only reply from my own experience.
Originally Posted by Tom Kershaw
IMHO, a (fairy) accurate "neutral gray" source is NOT necessary. Each ColorStar was bundled with samples, a neutral gray color negative; a neutral gray color positive (transparency); and one representing a ~ mid density black and white negative. As the result of a disastrous flood, all these were ruined, and I proceeded to make replacements. Color balance was never an issue; trying to produce a uniform density across the frame WAS. These are, as were the orignals. 35mm frames. I mounted them in plastic mounts, and marked them to enable me to align them in the same postion every time.
IF the process itself was sufficiently stable, agreement to some sort of "standard" would be - might be - useful. Color balance is affected by a number of variables, apart from ambient lighting. I've found significant variations between brands of paper; SIZES of paper within a specific brand; not only varaitons between different color developers, but between "ages" of mixed developers (at times, as little as three or four hours}. Add to this list, enlarger bulb age, dichro filter contamination ... I don't know - possibly the phases of the moon and or rising/ setting astronomical signs ...
Add to all that, aesthetics.
In short, I've learned to "go by the book" - it works - very well. The ColorStar is certainly NOT perfect - but it is, as certainly - USEFUL. I shudder to think of trying to print in color (again) without it
Ed Sukach, FFP.
I think I'll try and pick up an Expo/Disc next week and work through Mick Fagan's system, which should provide some good educational opportunities if nothing else. Although Ed I do understand what you're saying about the many variables in colour printing. I'm using a Nova tank system which seems far less precise than what I imagine a roller transport machine achieves.
I may plug the Colorstar 3000 into the voltage stabalizer that came with my DeVere enlarger. The standard mains supply voltage when tested was around 250V with little load, and visibly drops (i.e. lights get dimmer) when an instant water heater or other heavy load is turned on.
Last edited by Tom Kershaw; 07-03-2008 at 06:59 PM. Click to view previous post history.