Densitometer Questions

[kev curry]

Just picked up a X-Rite820 (color) densitometer. I have the operators manuals and the means to calibrate the unit but I'm still unclear on a few things.....ie What channel do I use to read B+W negs developed in NON staining developers ?? Whats the Visual channel and whats it for?? Whats the difference between Transmission status 'A' and Transmission status M and what are they for??

Thanks
kev

[Helen Bach]

With unstained B&W negs you shouldn't see much difference between the channels, especially after correcting for the density of the film base, but blue is a good channel to use for traditional silver halide printing. The general idea is to use whatever channel is most appropriate for the next stage of the process. If you are using a UV-sensitive medium as the next step there is a case for using a UV channel, mainly because of base density. The silver density does vary a little by wavelength, but this may or may not matter.

Visual is supposed to represent the spectral sensitivity of the eye (photopic) - ie mostly green. Status A is intended for colour materials that will be viewed (eg motion picture prints, slides) and Status M is intended for colour materials that will be printed onto other sensitive material (eg negatives, interpositives, internegatives). The spectral qualities of the filters are supposed to mimic the spectral response of the next stage. Status M may not be perfect in that respect because of its age, but it is a standard ('Status' refers to the standardisation of instrument specification so the measurements will be the same no matter which instrument they were made on).

Best,
Helen

[kev curry]

Thanks for the reply Helen.
kev