Different enlarger height - different colour balance?

[Giorgio_23]

Hello,
in these days I trying to make big color prints, up to 20x24.
I start with 8x10 test print to find the correct exposure and filtrature.
Then I calculate the equivalent time exposure for a highest enlarger head...
the time exposure is usually correct, but the color balance is different!!! To make a 8x10 print I use, for example, 20M 40Y, to make a 12x16 print i have to use 35M 40Y... it is normal? With a different enlarger height changes the filtrature? Why?
The question is: it is a problem of height or a problem of different paper, so 8x10 paper is a different stock respect to 12x16 or 20x24 paper? Changing paper stock can be change filtrature?
thank you very much
Giorgio

 

[Vaughn]

A couple things -- yes, if the 8x10, 12x16 and the 20x24 paper are not the same emulsion and/or if they have been stored/aged differently, they'll require different filtration levels to achieve the same color. The emulsion numbers should be on the packaging -- some color papers had guides on them to let you know how they differed from emulsion to emulsion. Don't know if they still do.

Also, if you have kept the aperature the same and just lengthen the exposure to go from 8x10 to 12x16 or to 20x24, then the increased length of the exposure can cause a color shift (basically a resiprocity failure). Sorry for the bad spellings! I have burnt in sky and had the color shift due to the longer exposure to that part of the sky.

Vaughn

 

[ic-racer]

Two things that make me NOT do it the way you describe:
1) As pointed out, you need to use paper from the same box.
2) There are psychological differences in how I interpret a small print and a very large one. Such that even if I can match the big one to the little one, I don't think it always looks the best it can be. I think the big one actually requires its own special interpretation of the contrast and density, etc.

 

[pentaxuser]

I keep on seeing a reference to guides/codes on boxes to indicate at least a starting point for colour balance. Since I started RA4 printing a few years ago I have never seen any such reference on Fuji paper or Kodak paper.

I have a feeling that Fuji never bothered and while Kodak did this was quite some time ago when emulsions varied quite a bit from box to box. It may have become redundant when the process and quality control got so good to render it unnecessary.

That's not to say that different size papers do not vary for several reasons, especially age and does not negate the suggestion that that when using large paper then it is sensible to do tests on smaller pieces of the same box of paper.

I don't think that enlarger height changes have much to do with the problem.

pentaxuser

 

[Bob Carnie]

The paper stock is the difference, not the enlarger height.

You may want to buy only 16x20 paper and cut down to smaller sizes.
Then you are good to go with the same emulsion for different sizes.
this will help you.
Be careful cutting down , wear gloves , and do not cut in sunlight.

 

[brucemuir]

the Supra Endura I have now that expired in 2009 is marked 45M 45Y

All the Endura products I've had in the last 5-6 years had starting filtration numbers and they were all close to the above numbers

on the other hand I never saw any numbers directly on a box of Fuji Crystal Archive (PIII i think it was)

 

[perkeleellinen]

I keep on seeing a reference to guides/codes on boxes to indicate at least a starting point for colour balance. Since I started RA4 printing a few years ago I have never seen any such reference on Fuji paper or Kodak paper.

All the boxes of Kodak paper I've bought have the codes, including the last ones I bought from AG Photographic before the stocks ran out. The code is on the bottom, on the sticker, quite near the edge. It always reads the same: "0C + 65M + 55Y" in bold black letters. Have a look, you'll spot it.

 

[pentaxuser]

All the boxes of Kodak paper I've bought have the codes, including the last ones I bought from AG Photographic before the stocks ran out. The code is on the bottom, on the sticker, quite near the edge. It always reads the same: "0C + 65M + 55Y" in bold black letters. Have a look, you'll spot it.

Thanks I must have another look at my one and only box of Kodak left. I have seen these filter numbers on the Kodak website. It would appear that while they are still printed, there is no variation to the numbers whereas years ago there were variations. In fact in the heyday of the publication of colour printing books they always made a point of stressing that you paid close attention to the changes from one box to the other.

The Fuji info on RA4 always left a lot to be desired compared to Kodak.

pentaxuser

 

[Nicholas Lindan]

Changing the exposure time will often change the color balance.

You should adjust the lens aperture to compensate for changes in print size. You need to use a meter for this - the click stops are not accurate enough. The Ilford EM-10 was designed for just this purpose.

 

[photo-Jon]

I agree with Nicholas. Adjust your aperture instead of time to compensate for the density of the print.

 

[George Nova Scotia]

You might also want to look for a lens that let's you disengage the click stops. IIR these where designed for colour printing with a meter. You could keep the time constant and fine tune the exposure with the apurture.