Predicting color balance and print exposure times.

[stevewillard]

I have an idea for precisely predicting color balance and print exposure times for color

negative papers. I am looking for your considerations.

 

First, let me provide you with the circumstances. I am a fine art landscape photographer.

To maintain quality control and consistency from print to print, I make a master copy of

each image I have. I use the master copy as a target when printing subsequent prints. I

have found that making precise copies of the master print to be very difficult if not

impossible without wasting lots of paper and time. I can do a better job by making test

prints than I can with a color analyzer, however both still fall short of my goal.

 

My overall strategy is to apply the analysis at the print level rather than at the negative

level as color analyzers do. This should eliminate all variables attributed to paper batch

and processing. I will be using a print densitometer for taking readings which is far more

accurate than a color analyzer. So here is my grand plan.

 

1. I will ?rough in? a test print that is close to the master print using the manual test strip

method. I can get close in two sheets of paper.

 

2. I will then select a critical area on the Master print and take a RGB reflective density

reading and a white light reflective density reading. I will then repeat this procedure on the

test print in the same spot.

 

3. The differences in the white light density readings will tell me the time change that I

need to apply to the test print to achieve the same density as the master print. I have

already done this using a linear interpolation and found that this method to be very

accurate provide the prints are reasonably close in density.

 

4. The difference in RGB readings will tell me the color head changes I need to make and

the times changes I need to make as a result of changing the filtration. These times will be

added to the white light time noted above.

 

Clearly, I will have to quantify the impact of unit changes in print density for both white

light and RGB readings would have on the color head and final print times. Once I have

done this, then I can develop an equation which inputs all the densities and computes time

changes and color head changes needed to generate a print that matches the master print

with a greater degree of accuracy and much less paper and time.

 

So does this seem possible? Has any body done something similar to this?

[kirk_keyes]

Go to www.phototechmag.com and look for the back issues that have articles by Bertram W. Miller (Millar?). He wrote a series of articles in the early 90s that I seem to remember covered this sort of approach.

 

You will need to figure out the response of the paper to exposure - make a print with a step wedge and then make some measurements of it with your densitometer.

 

I think Miller even had a computer program to help with this, put I'm not sure if it is around now, or even would run on modern computers...

 

Kirk