Colorhead settings change as height changes

[stevewillard]

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.

 

[Kino]

Your color temp is changing with head elevation?

 

[Lopaka]

Perhaps the change is due to longer exposure time?

Bob

 

[stevewillard]

I have a gossen color-pro 3F color meter, and it also shows that the color temperature of the light source changes as the height of the head changes. Is there any physics that can explain this?

 

[jd callow]

Perhaps the change is due to longer exposure time?

Bob

This is the only reason why I can imagine for changing the filter pack on hieght adjustments.

 

[Kino]

Perhaps it is because you are using a meter intended for field use, rather than spot readings of specific areas of a negative?

Don't most color analyzers for darkroom use have a direct reading, narrow sensor and the Pro F have a rather large integrating chamber?

Could be you are naturally getting a different area of the neg as you raise the enlarger head; an area of less, more or different total colors?

 

[Photo Engineer]

Filter pack should not change for any reason. Todays papers are adjusted to compensate and eliminate this problem. Something else is going on there.

PE

 

[jd callow]

Filter packs will change on longer exposures.

 

[stevewillard]

I used a "clear" 5x7 color negative that had an orange cast. I adjusted the color head for daylight balancing the the orange cast to 5500 degrees. My motivation was for making masks from color negative film using daylight balanced TMX 100.

As I adjusted the height of the colorhead I had to make adjustmments to the head to get a daylight balalnce of 5500 degress.

 

[Kino]

Interesting. No answer unless it is an equal, across the board YCM increase for density loss.

 

[jd callow]

The OP doesn't tell us what the changes are. In my experience I 've had to add Y as exposure time increased. If you are lossing density you add time prior to changing the th efilter pack.

 

[stevewillard]

I was hoping someone new of some physics that could explain this observation. As my sales for prints are increasing I need to start chararcterizing changes in paper batches, colorhead height changes, and changes to YMC with respect to exposure to help my efficiencies in the darkroom. My goal is achieve a perfect match in print density and color balance to my master print in three or less 8x10 test prints.

I must also note that my changes in colorhead height can be very large ranging form 8x10 to 30x40 or from 4x10 to 20x50. Small changes in colorhead height have very little effect on the color temperature of the light source.

I hope to be doing this in late fall of this year and publish my findings in hopes that others can benefit or note better ways of addressing these issues.

 

[jeroldharter]

I don't think the height is relevant but exposure time is. If you raise the height without opening the lens, exposure time increases which can result in color shifts. This happens routinely with Ilfochrome and there was once a good article about it in PhotoTechiques magazine.

I am not sure what you mean by adjusting to get a color temp of 5500. What sort of meter are you using?

 

[stevewillard]

A gossen color-pro 3F color meter. I think I paid around $1100 for it several years back.

I do change the aperture to keep the exposure times between 5 to 15 seconds so that I do not burn out the eight lamps in my colorhead prematurely.

 

[jd callow]

I was hoping someone new of some physics that could explain this observation. As my sales for prints are increasing I need to start chararcterizing changes in paper batches, colorhead height changes, and changes to YMC with respect to exposure to help my efficiencies in the darkroom. My goal is achieve a perfect match in print density and color balance to my master print in three or less 8x10 test prints.

I must also note that my changes in colorhead height can be very large ranging form 8x10 to 30x40 or from 4x10 to 20x50. Small changes in colorhead height have very little effect on the color temperature of the light source.

I hope to be doing this in late fall of this year and publish my findings in hopes that others can benefit or note better ways of addressing these issues.

I'd think no more than 2 or 3 test strips ripped from one 8x10 sheet would be need to match an 8x10 to a 30x40 of the same neg on the same paper. The time can be done by math using Inverse Square Rule -- confirm with your first test strip -- and the colour pack changes can be charted in advance (run a series of tests at 8x10 up through 30x40 and note the deviation) -- tested on the first test strip (remembering that light output is altered as filter density changes) -- or refigured with the second test strip.

Then all you need to do is put your paper down and print a full one to see how much crap you forgot to clean off the neg.

 

[stevewillard]

I'd think no more than 2 or 3 test strips ripped from one 8x10 sheet would be need to match an 8x10 to a 30x40 of the same neg on the same paper. The time can be done by math using Inverse Square Rule -- confirm with your first test strip -- and the colour pack changes can be charted in advance (run a series of tests at 8x10 up through 30x40 and note the deviation) -- tested on the first test strip (remembering that light output is altered as filter density changes) -- or refigured with the second test strip.

Then all you need to do is put your paper down and print a full one to see how much crap you forgot to clean off the neg.

Thanks JD. That is a great starting point.

 

[Nick Zentena]

A gossen color-pro 3F color meter. I think I paid around $1100 for it several years back.

I do change the aperture to keep the exposure times between 5 to 15 seconds so that I do not burn out the eight lamps in my colorhead prematurely.

Longer times won't [or at least shouldn't] hurt your bulbs any. The big issue is the on/off cycle.

Which might be your issue. Could the bulbs be going from cold to warm? Just a guess.

Why not get a Colorstar 3000 or the newer Jobo Colorlines 7000? Very simple to adjust times with height changes. The meter does it for you. You can program various papers into it. The oldest 3000 handles 8 different papers. The newer ones 100. Mark your master print with the areas you read and then just read the same spots.

 

[jeroldharter]

Longer times won't [or at least shouldn't] hurt your bulbs any. The big issue is the on/off cycle.

Which might be your issue. Could the bulbs be going from cold to warm? Just a guess.

Why not get a Colorstar 3000 or the newer Jobo Colorlines 7000? Very simple to adjust times with height changes. The meter does it for you. You can program various papers into it. The oldest 3000 handles 8 different papers. The newer ones 100. Mark your master print with the areas you read and then just read the same spots.

I second that. I have a Jobo Colorline 5000 that I used for Ilfochrome and it worked great. It requires some calibration and I don't think that the "wheel mechanism" and buttons are intuitive, but the Jobo is excellent.

 

[Photo Engineer]

Filter packs will change on longer exposures.

John;

I've gotten information from the designers of Endura emulsions who say that the color shift due to reciprocity failure is gone within normal exposure ranges for laser to tungsten light in all sizes. This would be in the range of milliseconds to minutes.

I have made 8x10 prints and 16x20 prints using the same color balance, merely changing the time / aperature settings to compensate.

PE

 

[jd callow]

Ron,
My experience is different, although I haven't made a print in 18 months maybe things have changed and or it may have something to do with the lamp output and not the paper.

 

[Photo Engineer]

Ron,
My experience is different, although I haven't made a print in 18 months maybe things have changed and or it may have something to do with the lamp output and not the paper.

There is a warm up and afterglow associated with some types of lamps, most notably tungsten. This increases the red output of the lamp and makes prints more cyan. The longer the light is on, the more the afterglow as the filament cools down.

I use halogen lamps.

PE

 

[jd callow]

As do I in my durst, but I'm unsure of what was used in the Beselers and Omega's I've used.

 

[stevewillard]

I have eight 250W halogen bulbs in my head. When I first starting printing I was using all three settings liberally like 90Y 50M 30C and very long exposures were the rule. I had no clue about what I was doing. I burnt out all eight bulbs in less then 6 months. Now my settings are more like 10Y 15M 00C, and I adjust the aperture so that my exposure vary between 5 to 10 seconds. I have not burned out a bulb in three years, and I am printing all winter long.

A lot of things I am noting here are based on memory and observations over long periods of time so the degree of accuracy is questionable. However, I am getting to a place where my sales demand that I can fill orders fast so I need to spend sometime quantifying all of these issues, if indeed, they really exist.

Recently I got a batch of 20x24 Fuji CA paper paper that significantly deviated from settings I have recorded in my database for my master print. I was very surprised. I do have a JOBO ColorLine 7000 color analyzer that I have never used. It has the ability to create a virtual master (VM) YMC setting, and then I can calibrate each batch of paper with respect to changes from the VM settings. These are called batch adjustment (BA) settings and could be recorded on the applicable box of paper. All settings in my database for the master prints would be VM settings. When I would set up my colorhead for a print, I would first set the VM setting and then add in the adjusts for the BA setting of the paper I am using. I think the JOBO will also compute print density setting using the same model. Of course, this is just another idea I will be playing with.

Just for the record I would never recommend a color analayzer for fine-art photography. They are designed for rough production lab work, but used in the manner I just outlined above, they may be a very productive tool.

 

[Mick Fagan]

2,000 watts of lighting, sounds like an 8x10 enlarger.

I don't know what you call long exposures, but in my book a long exposure is one where you set the timer in minutes, something like 5 or 7 minutes for an exposure. This is for mural enlargements using a 10x10 horizontal enlarger.

With a conventional vertical enlarger with 2,000 watts of go juice, unless you were enlarging with a 380 or larger lens at f64 or so, I wouldn't expect anything longer than about 25 seconds, 45 seconds tops, for the size of enlargements you are talking about.

Yes, the lights can go out, when one goes you do have to replace the whole 8 globes.

I would suggest with your reasonably short exposures for a 2,000 watt head, you may be getting minor colour changes due to lamp temperature fluctuations.

The best 2,000 watt tungsten head enlargers, always had a shutter in the head. That way the lamps stay on permanently (so to speak) and when you press the button your integral timer trips the shutter and away you go.

If you place a quite sensitive light meter under your enlarger, place some extra diffusion material above the sensor, then trip your enlarger in total darkness and watch the meter change as the exposure ticks on towards a minute.

I have the original Jobo Colorstar analyser made by Lici, it has a digital readout and I know that a powerful colour head will still be warming up for the first 5 to 10 seconds. In fact all tungsten lamps do, but with a power source as you have the effect can be noticed by paper more easily, than with a single tungsten lamp enlarger

Mick.

 

[Mick Fagan]

I forgot about the afterglow effect of all of those lamps, it is there, and with 8 globes a glowing

Mick.