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Sensitometry for stained negatives

BHuij

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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.
 

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?
 
Stephen Benskin said:
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?
Click to expand...

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+).
 
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
 
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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.
 
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
 
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".


 

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
 
Since VC papers are sensitive to blue and green, I'd think a cyan filter (#44 or #44A) would give more accurate results, but just for the one paper contrast that corresponded with the mix of green and blue passing through the filter. A blue filter, by the same logic, would only give you results for the contrastiest filtration for VC paper (e.g., all magenta or only blue light).

Best,

Doremus
 
Continuous agitation doesn't lose speed. I think there are some hints to what is going on in OP's description, for example finding a EI of 250 for HP5. If someone does a well controlled/careful, no-flare Zone System EI test, the EI by definition should come out 2/3 stop lower than the ISO speed. That would make 250 the expected Zone System EI for an ISO 400 film such as HP5.

In other words barring extreme procedures / materials / chemicals, the Zone System EI test isn't really providing information. It's testing the test.
 
FWIW, I've tested HP5 a few times over many years and my personal EI has always worked out to be 250. Also, I've run a CPP-2 for 30 years now and never measured any loss of film speed that I could attribute to rotary agitation.
 
The description of @BHuij testing methodology reminded me of the test method from How to Use the Zone System for Fine B&W Photography by John P. Schaefer. You place a step tablet on top of a sheet of film. Meter a target and open up 5 stops. If the speed set by the meter results in 0.10 density being reached at the point of exposure where the step tablet has a density of 2.70. Except if the steps are correctly followed, it will produce Zone System EIs which will be approximately 2/3 of a stop lower than the ISO. For it to work, either the exposure needs to be greater or the step tablet target density should be 2.50.
 

Not sure I fully understand your assertion here. Can you clarify for me? Yes, I (and others) have independently found that exposing HP5+ 2/3 stop slower than box speed (i.e., rating it at 250) is the best way to get proper shadow density when developed to a normal contrast range with HC-110 (i.e., one where Zone VIII reads 1.20 density). This is the first I've ever heard the notion of some universal rule that all 400 speed films have a fixed "Zone System EI" of 250.

For example, when I develop HP5+ roll films in Instant Mytol, I get normal development with Zone I density = 0.10 and Zone VIII density = 1.20 by rating the film at EI 500. That could be due to differences in developer, it could be due to less agitation, I tend to believe it's probably a mixture of the two. But I doubt whether I'd get a +1/3 stop boost to HP5+ effective speed if I rotary processed. Maybe I'm wrong; I probably ought to test that assumption at some point. Wouldn't mind at all having a true 500 speed sheet film option

As for agitation, I don't claim to my any kind of expert. My experience has been that using rotary agitation results in highlights developing much faster without shadows also developing much faster. Kind of an "anti-compensating" effect. The mechanics of how that would work make sense to me, since constant agitation is constantly refreshing the developer activity in highlight areas, not allowing for local exhaustion. So it's not that rotary agitation directly changes film speed as an inherent quality of the film, more just that it tends to make the highlights skyrocket to target densities faster, not allowing as much time for shadows to develop as far. The same phenomena is what lets stand development (and semi-stand, and EMA) bring out more shadow detail without blowing out highlights: local exhaustion.

I can't find the reference right now, but I could have sworn Sandy King noted a similar pattern in his writings about Pyrocat HD - rotary agitation requires more exposure of the film compared to stand, semi-stand, or EMA. I use EMA for roll films in Pyrocat HD and appear to get full box speed (at least with FP4+; pending further formal testing). The sheet I just did of HP5+ in Pyrocat HD was rotary agitated, and it looks like exposure is probably going to land somewhere in the 250-320 range. Not a huge difference, but less than box speed.

*shrug* makes sense in my head, maybe I'm wrong here.

At any rate, I'm off to see if I can find a thin piece of #47 filter to give me ballpark density readings from stained negs.

Is the procedure as simple as putting the blue filter gel with the negative when measuring? Densities will read lower overall I assume, but the 0.10 and 1.20 standard targets are "relative to FB+F" anyway, so does it all just come out a wash? Or do I need to actually adjust calibration here?
 

Traditional Zone System testing is Zone I is 4 stops down from the metered reading. ISO has the speed point Δ1.0 log-H (3 1/3 stops) from from Hg which is the metered point. They are different methodologies that will produce different values under the same conditions. While we're at it, have you ever wondered by a grade 2 LER for a diffusion enlarger is 1.05 while the Zone System NDR for the same paper is 1.20? Answer: Similar reason. It's an interpretation thing.
 
A long time ago, I teamed up with Kirk Keys over a similar question. He felt there was some special properties in staining and I believe it had more to do with the development velocity. We ran a bunch of film, but didn't get much past that stage. Below are the results for FP4P developed to a CI 0.56 in Xtol and PMK. Part of the print testing was going to determine which read densities best represented the results. If I remember correctly, I felt the Visual setting is most likely represent how the film would respond in an enlarger's light.

 
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When I did testing, I found HP5 to have a speed of 500 in Xtol in a Jobo, which makes sense as Xtol is known to have a speed increasing property.
 
First I should say that any EI is valid if it gets one to the desired print / tone reproduction with the least amount of effort and/or risk. Ultimately print (or scan) quality is what counts so if (for example) you find that things work better for you setting your meter to 250 when using HP5/HC-110, no argument from me.

When it comes to things like EI testing / Zone System sensitometry though, the people who wrote/write the books and teach it generally do a poor job explaining where the EI criteria come from, what they are based on, and why/how they relate to the ISO criteria.

To make a somewhat longer story (the lineage of the ISO speed criteria (and Zone System EI criteria) shorter, the difference between the two is that in the Zone System EI test you are looking for the 0.1 density 4 stops below the metered exposure, whereas in the ISO speed determination you are looking for the 0.1 density 3 1/3 stops below the metered exposure. And the reason for that difference is more or less because the ASA speed determination for black and white negative films was updated in 1960 to remove a safety factor of roughly a stop, while the Zone System EI methodology was never updated. That’s really all that’s going on. It’s why (barring extreme procedures, materials) when people do a EI test they generally end up with EIs around 2/3 stop lower than the ISO speed when targeting a normal gradient.

If you’re getting EI 500 with mytol/XTOL that seems quite high to me. Granted XTOL gives full emulsion speed and HC-110 might not always quite reach that, but a full stop difference is huge. Then again if, tests aside, EI 500 is working as well or better than any other EI in practice, no argument from me.

Regarding how to measure densities with the blue and green filters, I’m not all that familiar with the Dektronics but basically you would measure the densities through the filter relative to the base+fog measurement through the filter.


 
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Alan9940 said:
FWIW, I've tested HP5 a few times over many years and my personal EI has always worked out to be 250. Also, I've run a CPP-2 for 30 years now and never measured any loss of film speed that I could attribute to rotary agitation.
Click to expand...

same here. AFAIC HP5+ hasan EI of 250 vs a box speed (not ISO) of 400
 
The main issue is properly communicating the results. This why there are prefixes with most procedures. Different approaches will result in different results. Some might be more accurate than others, but for the most part, most are sufficient. The problem comes when communicating the information to someone else. When the ISO prefix is used, it means the standards were adhered to. The ISO prefix communicates the pros and cons of the method if you know it, and says that you should get similar results using the same method. CI means you've used the Contrast Index procedure, which could result in a different value than if you used gamma, or Bar-G. LER means the range of the paper tested is from 90% of Dmax to 0.04 over paper base.

EI is how you set your camera. It has no specific meaning on how it was produced, which is a shame. Just saying EI 200 doesn't convey anything about how it was determined. It could just be a feeling. One of my pet peeves is when people say take the manufacturer's development recommendations and reduce development by 15%. This might be good advice for some as it might work for people using a condenser enlarger while the manufacturer's development recommendations is for diffusion enlargers, but wouldn't the communication be more helpful if the recommendation stated the situation?
 
Fascinating discussion so far. I did not know that Zone System testing and ISO speeds were fundamentally 2/3 of a stop different from each other. I've always just used the (I suppose less precise) terms of "film speed" or "EI" to describe the value I set my meter to.
 
An ISO film speed also needs to say what developer was used. It used to be that D76/ID-11 was the standard developer, but now other developers can be used as long as it is specified. That's how Fomapan 200 can claim to be a 200 film, they used Microphen to get the most speed they could out of it, plus used a non-standard Gamma of 0.8. When developed to a more normal contrast gradient the speed is about 80 in Microphen.

So I can see ISO 400 from an HP5/ID-11 combo and 500 from HP5/Xtol, as Xtol gives just a touch more speed than ID-11.
 
The ISO gamma in the Kodak workbook is also quite high right? It's 0.8, where we'd normally aim around 0.5 for silver gelatine. That pulls the toe up a bit higher that we'd get under normal dev.
 
I don't see that in the workbook. There are different ways of measuring contrast but I think the example for gamma in the workbook is 0.63. That corresponds with the required slope between the speed point Hm and Hn in the ISO standard.

ID-11/D-76 was never the required developer for ASA/ISO speed determination. Up until 1993 the ISO standard specified a formula. In 1993 that requirement was removed and the film manufacturer could then use any developer as long as it was disclosed upon request.

The contrast parameter did not change in the standard. So, for the Foma 200 example given above, the Y-axes of their graphs should not be labelled ISO. They are EIs, and in each case there would be one EI meeting the ISO speed criteria. Based on the data Foma provides that speed seems to range from roughly 125 to 160 depending on the developer. Labelling the film "ISO 200" is then incorrect unless the film somehow reached that speed using some other developer, in which case if asked, Foma is supposed to provide that information. However if you read the standard that is obviously not the intent. Using some kind of special purpose, non-commercially available developer specifically to squeak out an ISO speed which can never be realized in practice wouldn't be very useful to customers.

An additional interesting thing about all this - in the underlying speed determination method the "speed" isn't as sensitive to +/- variations in gradient as the Zone System EI usually is.

tcolgate said:
The ISO gamma in the Kodak workbook is also quite high right? It's 0.8, where we'd normally aim around 0.5 for silver gelatine. That pulls the toe up a bit higher that we'd get under normal dev.
Click to expand...
 
For the sake of other in the thread that want a quick reference, the workbook is here
Milpool said:
I don't see that in the workbook. There are different ways of measuring contrast but I think the example for gamma in the workbook is 0.63. That corresponds with the required slope between the speed point Hm and Hn in the ISO standard.
Click to expand...
Sorry, you are quite right, I was scanning too quickly. gamma is 0.63, but that's still higher than we'd want for regular silver gelatine print. So the traditional ISO evaluation method over develops vs where we might normally want to get to, getting you to the 0.1 above base fog a little earlier than you would otherwise. I've heard people attribute the often stated "need to over expose 2/3rds of a stop", to this additional over development.
From what I've read elsewhere, d-76 is the closest we have to the original formula they provided. If someone is doing their own sensitometry right now though they are likely doing it to check the speed they are getting with their developer of choice and agitation regime. Since they are setting that on the ISO dial, I think occasional slips to refer to it as ISO are perhaps forgivable.
 
For reference here is the original specified formula. It's different than D-76/ID-11. Apparently one of the reasons for the standard change to remove the specified developer was that Kodak had trouble getting the earlier T-Max films to quite reach box speed with it (recall there was a time when the T-Max films were labelled EI rather than ISO).

(/l)
0.5g metol
40.0g sodium sulfite (anh.)
1.0g HQ
1.5g sodium carbonate (anh.)
1.0g sodium bicarbonate
0.2g KBr

pH 9.4 +/-0.2 @ 20C

At that time the standard also specified the fixer formula.

Regarding gamma in the standard keep in mind this is required between the speed point (Hm) and a point Hn 1.3 logH (4 1/3 stops) higher. In Zone System parlance that would be the range from Zone I 2/3 to Zone VI.


 
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