Reflection Densitometer Use

[Luis-F-S]

Hi,

I've owned a transmission densitometer for quite some time and used it for evaluating negatives and determining film speed and development times. I've recently bought a reflecton densitometer, but not sure how useful a reflection densitormeter is for b&w photography. How do you have one and how do you use it?

[Pere Casals]

Luis, reflection densitometer allows paper calibration in the same way film can be calibrated, it is useful to plot sensitometric curves (for all contrast grades) for paper showing density in the print from lux·second exposure.

Let me tell an example. You want a cheek in a portrait to be in Z-VI because caucasian subject, you check the graph and you find that such density is obtained with 20 lux·second exposure. Then with a luxmeter you find that the cheek in the enlarger projection has a light intensity of 1 Lux, then with 20 seconds exposure that cheek will have the amount of density you want.

Once you have the exposure for the cheek then you can make other readings in other interesting spots of the projection, and in the graph (of the used paper grade) you can find what density you will obtain in those spots. Then you check if obtained density is the prediceted, for feedback.

First half of Beyond the Zone System book explains all those calibrations, a recommended reading.

Of course we can adjust a print in a lot of ways, but IMHO using graphs to predict results is a very Pro approach that saves time and paper.

A reflection densitometer can be substituted by scanning the print alongside with a density gauge, and comparing.

[AJ Edmondson]

For me the reflection densitometer has been most useful for relating the density range for varied VC filters to the actual negative densities... pretty much what Perl Casals said. Once you can associate a known negative density with a certain tonal rendition and then actually see how the other densities in the negative relate to that value with the different filters you can really fine-tune the negative development process for your own vision. It has been the most valuable tool at my disposal for adjusting the printing process and doesn't require excessive "boring" testing - expose a step-tablet, develop and dry and record the readings and you can quickly predict how the different filters relate to your negative densities.
Joel