[Tig] Printerlights

peter_swinson at compuserve.com peter_swinson at compuserve.com
Fri Dec 10 17:49:04 GMT 2010


 
Film Labprinter points were/are established using Color film analysers, (Hazeltine,FilmLab etc) where the grader (timer) scans the negative and adjusts the RGBvalues to obtain the correct “look”. There are no such things as separate lift,gamma, gain or other adjustments. The printer points reflect what will happento the film print color and density when the printer RGB illumination isadjusted to match the printer points. Each printer point is a change of0.025loge. Printers have RGB printer point values from 1 to 50.
 
For thosestill with me, a change of 0.30 loge is one stop, or 2:1 change in illuminationbrightness. Therefore each printer point change is about 8% of a stop. 
 
How thiseffects the printed image is further compounded by the film negative having aDensity vs Exposure (DvsE) curve of less than unity. And a print stock D vs  E greater than unity.  All of these curves need to be taken intoaccount in determining the actual effective printer point relationship tocurrent D.I. operations. 
 
The“reported” printer points to the DOP, was and I guess still is the valuesneeded to make the shot both a neutral balance and “perfect” technicalexposure. It will give an experienced DOP an idea as to how the shot isrelative to his desired image.  For example  a DOP shooting day for nigh may get a report of “25” across, 25 R 25G 25Bwhich means it was perfectly shot as a average lit scene. He will then knowthat when printed it may, for a day for night effect, need to be printed at45,45,30. In other words higher printer illumination to  make the print dark but not making the bluequite so dark, therefore giving a colder look to the image.  
 
Many yearsago Rank Cintel developed , at the request of several DOPs, an automatic methodof determining a set of RGB printer point values from a shot negative. I tghinkit was called DME.  However the systemnever caught on as it required a fixed grey card to be recorded in the scenebefore the action, something that rarely happened!
 
This isprobably telling you how to suck eggs, but thought I would exercise the oldbrain cells anyway !!!
 
Cheers
 
Peter



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