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RH Designs Analyzer Pro Calibration and the Callier Effect

Dan Rainer

Member
Joined
Mar 28, 2024
Messages
60
Location
Georgia, USA
Format
Multi Format
I own an RH Design Analyzer Pro and I've really enjoyed the product. To calibrate the contrast at different grades, the manual has the user contact print a Stouffer 21 Step Wedge onto their paper of choice and then find the difference between 0.04 and 90% dmax. This results in an ISO(R) number that can be plugged into the device and also used for sensitometry analysis.

I'm new to sensitometry and I'm currently reading Beyond The Zone System. In BTZS, Davis discusses the Callier Effect and says that contact printing a wedge will yield less contrasty results than projection printing. If this is the case, would it make the recommended calibration of the Analyzer Pro inaccurate? Or is there some sort of pre-programmed offset to account for the increased contrast when projection printing with my condenser enlarger? I'm also assuming that sensitometry data and graphs gleaned those test strips is completely useless if I'll be using the paper for enlarging. Is this correct?
 
I own an Analyzer Pro as well and have followed the calibration instructions for the papers I use.

FWIW, I wouldn’t worry too much about exact accuracy of the calibration. If it’s getting you to a reasonable starting point on the first print, then I’d say it’s probably good enough. No matter how accurate the calibration is, I’m sure it’ll take a few iterations to get the print to where you want it anyway.
 

I know the calibration is just for a ballpark starting point. I'm not expecting to look at some LEDs and make a fine print on my first attempt lol... I'm more so just curious about the Callier Effect and how it relates to print contrast. If I were to projection print the step wedge would the ISO(R) numbers be significantly different? If so, does RH Designs program in some sort of contrast offset into their device?
 
I don't think the caller effect is relevant in this case because what you are trying to measure is the actual ISO (R) at the easel (paper). Having calibrated the Analyser, the Analyser will replicate what the step wedge contact print produces -- ie, the 'off white' parts of your print will be off-white and 'near black' parts of you print will be near black.
I agree with previous posters, calibration is just a ballpark starting point -- in practice, the location of the midtones are far more important. I don't know how many times I've got the 0.04 and 90 points correct, but made an absolute hash of the midtones (the main interest of the print). So, in practice, I use the Analyser's fantastic test trip function to select the best exposure for the midtones and then use the burn (DIFF) function to get a decent print.
 

In my experience, the Calier effect only has aµarginal influence. In fact, it was so small that it was extremely difficult to determine a reliable Caliernumber to compare between a condenser and diffusion enlarger
 
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