<collective groan> sensitometry question

[MikeSeb]

In an effort to get more consistent results from 400TMY, I've done a bit of testing. I realize I'm a long way from formal Zone System testing with this; I wanted to get into the ballpark at least and refine through further empiric testing. I'm shooting roll film in several different cameras.

For 400TMY exposed at box speed and processed in a Jobo in straight Xtol, I get the following density readings of my spot-metered 18% gray card, placed in the listed zones:

fb+f ..... 0.13
I ...........0.16 (absolute, not net of fb+f)
II ..........0.22
V ..........0.73
VII ........1.04
VIII .......1.23

This data seems to indicate that I'm underexposing and underdeveloping the film. Am I off base here?

It looks like I'm getting zone I densities only at Zone II or higher, indicating my actual film speed is more like 200-250. And I'd say that I'm underdeveloping as well, by how much I don't know.10 to 15% maybe?

These readings correspond with my eyeball estimation of the problem: wan flat negatives that just sorta lie there.

Now, I do print via off-topic means not involving an enlarger and I'm not going there, here. And for such an output one wants a "thinner" negative for best results. But the current state of affairs is not satisfactory, and I'd like to start with the best possible negative.

I'm a little surprised not to get box speed from 400TMY in Xtol....

Thoughts appreciated.

 

[Tom Kershaw]

Mike,

There is a hugely long thread here ((there was a url link here which no longer exists)) that goes into some of the considerations surrounding film speed and exposure, at least as far I as I got to page 7 so far. A summary might indicate that it isn't surprising you're testing 200-250 as the correct exposure but that doesn't mean 200-250 is the speed of 400TMY-2 in XTOL...

IIRC, you process in an ATL-1500? - If so I've produced good negatives in contrast terms from subdued winter days with snow using T-Max 400 and XTOL processed in a Jobo , so good results are possible.

Tom

 

[MikeSeb]

Thanks Tom. Quite a thread.

Yes, a 1500. And I've also had good results with this combo; it's just that I'm struggling to get them consistently.

So I wanted to start over with fundamentals and make sure I'm doing the right stuff.

 

[Tom Kershaw]

I've tried to get back to basics recently as well. Hence doing some additional reading into the various considering around the Zone System, ISO speeds etc. The thread makes a case for being skeptical about strict adherence to a fix "correct" film exposure index.

Tom

 

[MikeSeb]

Yeah, Tom, that point came through rather clearly and emphatically.

The root of my problem is my incessant hunt for the "perfect" film/developer combo, plus doing a bit more B&W lately after a hiatus during which I shot almost no B&W in favor of color negative film. I'm old hand enough to know that "perfect" doesn't exist; but then again, all those tenderfeet who went West in search of gold also knew their odds!

What I'd like is to be able to dial in at most 2 or 3 B&W films and 2 developers I can use intermittently with good, predictable results. Like maybe 100TMX, 400TMY, and Tri-X or HP-5.

Xtol has been my mainstay developer since four or five years ago when I was shooting mostly B&W. It seemed to work pretty well for most films with straight or 1+1. But returning to B&W after my color-only hiatus, I find I'm having a tough time getting consistently good results with it, plus I'll have a tough time running through 5 L of it before it spoils. I've used a Jobo throughout, so I'm not sure what's changed--the films, maybe?

To me, 400TMY looks great in D-76, but ditto the shelf-life issues. I guess I could also standardize on this old standard, and mix up a liter of D76H when I need it.

I also have HC-110 and TMAX developers on hand, both attractive due to their long shelf lives. I had pretty much eschewed HC-110 due to its 2/3-1 stop speed loss, but if I'm going to have similar EI's with Xtol then it hardly matters. And Tri-X @250 looks better in HC-110 at 1+40 or 1+50 than in just about anything else I've tried, so that could be one possible prime combo.

TMAX developer is underrated, IMO. It's pricey, but does a great job with a number of films. Not as fine grained as Xtol but good shadow detail, less propensity to blow the highlights, and good storage life.

Going back thru my archives of scanned images to see which combos appeal to me the most. We'll see what turns up.

Any other thoughts, people? Thanks much.

 

[df cardwell]

Gosh, Mike.

What if there was a correlation between the (ratio of agitation to the development time), and the relationship of Zones II, Zone V, and Zone VIII ?

If you were to reduce the agitation, say 50%, and extend the development time to maintain Zone V density, you would find that the Zone II would have higher density, and Zone VIII, slightly less. But you can't do that with a Jobo, so you must increase the development time and allow your densities to rise until you have restored your desired local contrast. That works fine, and the only way to determine THAT is by printing... arbitrary density readings mean nothing because they have no connection to your printing medium.

Since you use an Alternative Enlarger, you have more than adequate density for reproducing detail below Zone II. As for the Zone VIII, that is up to you and your Software, and Alternative Enlarger.

For Jobo, I would use dilute XTOL, one shot. The results will be more consistent, and possibly you may make baby steps to reaching box speeds, and good local contrast.

Again, the Alternative Enlarger System will determine what the negative needs to be, just as a Traditional Enlarger, Paper, and Developer defines the shape of the curve your film must achieve.

d

 

[2F/2F]

This data seems to indicate that I'm underexposing and underdeveloping the film. Am I off base here?

IMHO, forget the data about what densities correspond to what print tones, and make your own list. Make a normal print on your normal paper and see if the tones you shot look normal when printed normally. If they do, everything is normal. If they don't everything ain't normal, and you can adjust things till they is. What densities you need for certain print tones will vary from paper to paper quite noticeably, IME.

Also of note is that to get a proper middle grey from a reflected light reading, you should open up 1/2 to 2/3 of a stop from the indicated reading. This alone accounts for much of why people almost always find slower film "speeds" with Zone System testing. The slight variation in middle grey values between different light meter manufacturers is another big reason.

Because of the 1/2 to 2/3 stop thing that I learned here on A.P.U.G., I am restesting FP4 and HP5 for when I want to use the Zone System. I am now downrating all my negative films by two EIs before even doing the initial test. E.g. FP4 at 80 and HP5 at 250. I have working EIs for both films so far that are each 1/3 EI higher than box speed (160 for FP4 and 500 for HP5), but I am basing this on eyeball examination of prints, not on measured densities. Have not tested for normal development yet, but I can tell that manufacturer's recommended is pretty close.

For standard exposure methods (i.e. incident meter), I ALWAYS use box speed, and simply learn how each film renders certain luminance ranges.

 

[MikeSeb]

Well put, Don. You're right; about the only thing I dislike about the ATL-1500 is that you have but one rotation speed to work with. So that leaves time and dilution as your only practical development "controls."

It's always been held by "them" that for the Alternative Enlarger one needs a "thinner" negative; very dense highlights are a no-no. I think this means, in practice, expose generously and develop sparingly. I think I might have been miserly with the exposure, and too enthusiastic with the "develop sparingly" admonition. I generally have decent highlight detail to work with, meaning that my Alternative Enlarger is able to "see" in those regions; but the rest of the image is just a pallid corpse of gray. I exaggerate, but you get my drift. So increase exposure by nudges, and increase development "extent" by nudges until I'm there.

I realize that I could make this all go away by simply scoring a nice LPL Saunders enlarger and building a darkroom, but that is just not possible in my current life. And the hybrid workflow for color is just perfect for me for a slew of off-topic reasons. So soldier on I must with this setup that is anathema to many of our fellows here!

thank you.

 

[ic-racer]

What 2F/2F said. In other words, the ISO/ASA film speeds came from backward analysis of negatives from [analog] prints evaluated by a panel of viewers. So, you could make some good prints [or what ever you all call them ] and work backward to see what your minimum exposure needs to be for your 'alternative' purposes.

 

[Thomas Bertilsson]

I realize that I could make this all go away by simply scoring a nice LPL Saunders enlarger and building a darkroom...

I don't know how much film you process, but how about not using the Jobo and soaking your film in daylight tanks where you agitate on your own? That would also enable you to get rid of the problem.
I can get away with shooting at box speed by extending development time, just like Don says (he taught me, for crissakes), but I do need to slow down agitation and let the film rest.
I understand the convenience of a Jobo, but it can be rather limiting, and the fix seems... easy?

 

[tlitody]

The root of your problem is this.

Film manufacturers rate their film speed based on the ISO standard. The ISO standard uses a set contrast index as the target film contrast. That film contrast is designed to fit paper using a nominal grade 2. It is also based on a set subject contrast range.

The very important thing to understand is that the subject contrast range they use is what is considered, by testing large numbers of subjects, to be the average scene contrast range. And that average scene is only 7 to 8 stops of contrast and not 10 as in the zone system.

What that means is that you don't have 5 stops above and below the metered value. You only have 4 when you are using the film box speed and recommended development.

check your data and you will find that that is what is you have got. i.e. you have got box speed but only for an 8 stop range and not 10.

But change your requirements to use 5 stops above and below metered as in the zone system, and you need to give extra exposure ( reduce film speed) and less development to arrive at a film contrast index which fits the paper.

In other words, by using 10 stops as normal subject contrast range as in the zone system, you will always lose some film speed to get there. That is not the film manufacturers over rating their film speed. It is you deviating from what is considered an average scene contrast range.

If your subjects were typically humans in a scene with little or no sky in them, you would find that most of your images would look flat if you base normal on being a 10 stop subject contrast range.

You will never get full film box speed if you use a 10 stop range and have verified that zones actually print where they should using zero filtration. The exception to that is if you use a speed increasing developer.

 

[tlitody]

I would add that as part of your testing to verify that zones print where they should, you should take a zone 1 neg and print it by making a test strip to find the print time for it so that it prints as just perceptibly lighter than black.
Then take a zone 9 neg and print it with the same time. It should just show a hint of tone.

I do this without using any filtration. The results are surprising if you believe that a net density of 1.3 is a zone 8 target. I find that a net density of 1.3 is a zone 10 but your mileage may vary as it will depend on your enlarger and the developer you are using. You must use fresh/new paper when doing this as paper contrast can drop off significantly as it ages.

Using target values set by ansel adams long ago when materials were very different is not necessarily a good thing. Many do use them and accept them as being correct but it is very subjective. After all, how often have you made a print and thought that looks pretty good only to look at it some time later and think it looks too dark or too light. Our perception of what is right changes as often as the wind.

 

[tlitody]

I'd have to ask why you are calibrating to a 10 stop system. Surely the typical subject brightness range of what you are photographing should determine what you calibrate to and not some arbitrary system.
i.e. If you are photographing landscapes with bright skies most of the time then sure, calibrate to 10 stops. But if you are shooting portraits most of the time then 10 stops will be too much so you should calibrate to a shorter subject scale.

 

[tlitody]

You have to start somewhere.

Thats true and the place to start is to go out with a spot meter and take some readings to find out what your typical subject range is. That way you get some real world targets to aim for when you do your film testing.

 

[tlitody]

I'd hazard a guess that you need to use 200 speed. As for dev time I'd say you definitely don't want any more. Whether you want less depends on what your target is for zone 8. Leave it as it is and you will get approx 1.3 above b+f. For me that is too much and I would reduce dev by about 30%. But for you and your system I really couldn't say.

If you use 200 as your speed, then your current zone 8 value becomes your new zone 7 value if you use the same amount of dev. You shift the curve left.

p.s. Excel is your friend. Just build a little spreadsheet with a graph which plots your data. Interpreting it then becomes simple and seeing whether you need more or less or the same dev becomes obvious once you have ascertained what you really want in the way of zone 8 or 10.

 

[Saganich]

In order to get box speed with your process requires a developer that will provide a lot of compensation with constant agitation. There is only one method I can think of that would do that, a D23 split process with either borax or Sodium Metaborate Octohydrate. I would also venture that D32 at 1:3 could also work in your situation with only a slight to no loss of speed. The idea is to get a greater curve slope between Zone I-V then V-X.

 

[tlitody]

well yes you can use a compensating developer but do really want to compress the highlights. Sometimes but mostly no since you have already compressing 10 stops into paper which only shows 7 stops. i.e. highlights can begin to go muddy looking.
But then using the unmentionable method of printing allows greater freedom for playing with what you have on the neg.

 

[Stephen Benskin]

Michael,

It looks like the processing is close. What I'd do is to make some negatives using slightly different EI settings and evaluate the results. Just like with film speed, matching the negative density range of the film to the log exposure range of the print comes from psychophysical research and there aren't ridged boundaries between acceptable and unacceptable quality. In fact, Loyd Jones found that there wasn't necessarily a precise correlation between the two but he couldn't a better method of defining the relationship between film and paper. Flatter scenes looked better when the NDR was greater than the LER and scenes with a higher luminance range looked better when the NDR was less than the LER. Tonal distribution (simultaneous contrast) and amount of print viewing illumination also play a factor. Counter-intuitively, darker tones appear lighter and lighter tones appear darker under lower lighting levels. You are close enough with you testing to do some field tests and see if the results work for you and your conditions.

 

[Stephen Benskin]

well yes you can use a compensating developer but do really want to compress the highlights. Sometimes but mostly no since you have already compressing 10 stops into paper which only shows 7 stops. i.e. highlights can begin to go muddy looking.

I don't have enough time to go into too much detail at the moment, but the 10 stop/ 7 stop question you propose is less of a reality and more of a communication problem between the two methods. The statistical average luminance for a scene is 2.2 log units or 7 1/3 stops and they represent the range of the shadow detail to a diffused white. The 9 or 10 stop range comes from the accent or cavity shadow and specular highlights. On page 468 of the third edition of The Theory of the Photographic Process says, "The problem of deciding how to define the log luminance range of the scene, for tone-reproduction studies, is usually solved arbitrarily by taking the log luminances interval between the deepest shadow in which detail is visible and the brightest diffuse highlight. Whenever this definition is adopted, however, it should be recognized that important semispecular and specular highlights and probably less important shadows usually lie outside the log luminance range indicated."

If you look at the density values Adams proposes for Zone I - Zone VIII, a 7 stops range or 2.1 with a negative density range of 1.25 equals a gradient of 0.59 and compare them with the current tone reproduction model, desired negative density range of 1.05 with a scene luminance range of 2.2 with a 0.40 value for flare. That becomes 1.05 / 2.2 - .4 for a gradient of 0.58. So there really isn't any difference between the two.

The standard model of exposure for a 2.2 range scene is that the highlights fall 0.95 log units above the metered exposure and 1.25 log units below. Ifyou factor in the standard flare value of 0.30, you get 1.25 - 0.30 or 0.95 log units below the metered exposure. This comes out to be just under 3 1/4 stops on both sides of the exposure.

 

[tlitody]

That was more than enough detail