Measuring Densitometry of Slides and Negatives

[adamlugi]

Since it’s currently not possible to purchase calibration strips for both processes, and considering that JOBO chemistry — which is now regarded as the best option for slide development — has become available, I’d like to ask for advice on how to optimally perform densitometer measurements and what the correct reference values should be.

My goal is to verify whether my development times are accurate.

 

[John Salim]

Why do you say it's not possible to buy calibration ( control ) strips ?
Strips for all processes ( E-6. C-41, ECN-2 & B&W ) are available.

You'll need a densitometer ( with the correct filters ), plotting charts, manufacturers process control manuals and some training to start taking control of your processing quality.

John S

 

[adamlugi]

Thank you for your reply. Could you please tell me where I can purchase E6 control strips?


I have an X-Rite 810 densitometer. Could you also tell me more about the filters?

Regards
Adam

 

[xkaes]

As with any "testing", it can be as complex as you want to make it. You can get great density readings from some simple gear under an enlarger. I've used a Minolta Autometer II with an enlarger attachment and a Beseler PM2L color analyzer to make graphs. There are other enlarger meters that run about $10 used of course.

 

[Mr Bill]

I have an X-Rite 810 densitometer. Could you also tell me more about the filters?

Hi, most likely John S is referring to "filters" built into the densitometer that help give it the correct spectral response. These so-called responses are designated with letters, such as status A, status M, etc. The standard X-rite 810 uses, in transmission mode, what they call status M which is proper for color negative film.

For the reversal films the proper densitometer would have status A response. A proper lab would use such a densitometer for E6. But in truth the spectral differences are not all that great; I would guess (this is strictly a guess) that your densitometer would be sort of ok for amateur work. (I'm assuming sloppy tolerances)

I’d like to ask for advice on how to optimally perform densitometer measurements and what the correct reference values should be.

If you want fairly complete information look for Kodak's Z-131 manual; this is for the C-41 (color neg) process. (It has different sections for different types of processing machines, so you only need the pertinent sections,)

Regarding "correct reference values, "when you buy a package of "process control strips" there will be one already-processed "reference strip." You read this strip with your own densitometer, and whatever readings you get become your aim reference values. Actually this reference strip is not quite perfect, so it will also come with a set of "correction values" to fix the imperfections.

When you plot the density values on a chart you are actually showing how your own processed strip differs from the reference strip.