Sensitometry for stained negatives

[BHuij]

I recently picked up a Dektronics Printalyzer. For normal B&W density readings it has been phenomenal. So far I've only used it for transmission readings with negatives, but I'm sure I'll get to reflective print readings before too long. I'm not new to the concept of testing exposure and development by reading Zone I and Zone VIII densities to establish (N) film speed and development times. I am fairly new to Pyrocat HD though.

For the purposes of dialing in speed and development, I have so far followed my normal procedure, the standard "put a piece of tape on a step wedge to get a totally opaque piece of it, then stick it in front of the film in the film holder, and expose a sheet at Zone X against a neutral featureless background in open shade" approach. I have developed and dried my negative.

For the purposes of printing on variable contrast silver gelatin paper with a normal enlarger (as opposed to something like graded/azo paper, or UV-based alt process), is there a way to get useful density readings this stained neg with my B&W densitometer? The research I've done to this point suggests that a color densitometer using the blue light might work. Is there a blue gel I could use to simulate the same effect since the Printalyzer is not a color densitometer?

I am aware of alternative testing procedures that don't measure negative density directly, and use contact prints of the step-wedge-imprinted negative and eye tests. Maybe that's where I'll land eventually. But I just got a new hammer and it seems worth checking to see just how much this "calibrating stained negatives for silver gelatin printing" problem is shaped like a nail.

 

[Stephen Benskin]

For the purposes of dialing in speed and development, I have so far followed my normal procedure, the standard "put a piece of tape on a step wedge to get a totally opaque piece of it, then stick it in front of the film in the film holder, and expose a sheet at Zone X against a neutral featureless background in open shade" approach. I have developed and dried my negative.

Just out of curiosity, when using this approach with general purpose developers, where does the film speed tend to fall in comparison with the ISO speed?

 

[BHuij]

Just out of curiosity, when using this approach with general purpose developers, where does the film speed tend to fall in comparison with the ISO speed?

Very developer dependent, and dilution/agitation also seem to have a huge effect, with lower dilution sometimes giving compensation effects (so in essence, higher film speeds), and with more agitation generally having the opposite effect.

For example - I do all my sheet films with rotary agitation. It lets me be super economical with chemical use, and gives me perfectly even and consistent development. But the constant agitation has a trade off of lower film speeds. I have tried to compensate for that by generally using weak concentrations and longer times, but HP5+ sheets in HC-110 1:100 still only give me an effective speed of 250. Rodinal is even worse with FP4+ sheets - I have to shoot at 64 to get proper shadows, even using 1:50 or 1:100.

For roll films, I use steel tanks, and the most I ever agitate is the Ilford standard (10s at the start and 4 gentle agitations over 10 seconds every minute thereafter). With some developers like Pyrocat HD, I'm actually doing basically EMA with roll films (1 minute to start, 5 seconds of gentle agitation every 3 minutes from there). That seems to buy a lot more film speed, especially when paired with phenidone-ascorbate developers like Instant Mytol and FX-55. I get full box speed with Pyrocat HD and FP4+ done this way, and about 1/3-2/3 of a stop boost with every film I've ever run through Mytol (Delta 100, FP4+, HP5+).

 

[tcolgate]

I've used Kodak wratten gel filters, a 47b B and a 58 filter. You have to recalibrate against the calibration strip with each filter, but that's pretty quick. I think it skewed a non stained test strip slightly, but not enough to worry about. Stained negs seemed to give credible results
It is on the vergess of the spectral curve for the device though, so it's definitely a compromise option
Edit: make sure you've got the transmission light on the brightest setting

 

[Alan9940]

Like @tcolgate, I use a #47 Dark Blue gel and, as mentioned, it's a compromise but comes close enough that I can "adjust" from there.

 

[tcolgate]

By was of an example. The green curve seems to always be very close to the white light, probably not worth the effort, but the blue consistently shows extra density with my pyrocat negs. (days here got a bit skewed as I misread my lux for the neg exposure) The tick up on the end is likely an artefact of Google Sheets plotting

 

[Milpool]

That makes sense and I have found the same generally when doing this sort of approximate densitometry with stained negatives - although you can occasionally see similar results with some non-staining developers as well.

The blue light and green / white curves are reasonable approximations as "bookends".

View attachment 412988By was of an example. The green curve seems to always be very close to the white light, probably not worth the effort, but the blue consistently shows extra density with my pyrocat negs. (days here got a bit skewed as I misread my lux for the neg exposure) The tick up on the end is likely an artefact of Google Sheets plotting

 

[pentaxuser]

For example - I do all my sheet films with rotary agitation. It lets me be super economical with chemical use, and gives me perfectly even and consistent development. But the constant agitation has a trade off of lower film speeds. I have tried to compensate for that by generally using weak concentrations and longer times, but HP5+ sheets in HC-110 1:100 still only give me an effective speed of 250. Rodinal is even worse with FP4+ sheets - I have to shoot at 64 to get proper shadows, even using 1:50 or 1:100.

For roll films, I use steel tanks, and the most I ever agitate is the Ilford standard (10s at the start and 4 gentle agitations over 10 seconds every minute thereafter). With some developers like Pyrocat HD, I'm actually doing basically EMA with roll films (1 minute to start, 5 seconds of gentle agitation every 3 minutes from there). That seems to buy a lot more film speed,

So those who use constant agitation lose speed by so doing? I wonder why this is? Ilford makes no mention, as far as I know, of this phenomenon but simply that constant agitation reduces the time needed to achieve what intermittent inversion achieves

Thanks

pentaxuser