Tmax 100 characterisitic curves

[gteeter]

Recently I've been testing Tmax 100, and I was hoping to get some advice/feedback on the results. I attached a plot. I'm puzzled by the decrease in contrast that shows up around zone IV, which gets more pronounced with increasing development. Also there is a decrease above zone XII. I don't know if this is the shoulder, or if it's an artifact of my testing procedure.

Obviously this won't prevent me from using the film, I just don't understand what's causing the apparent decrease of contrast in the midtones and wonder if anyone has seen similar effects, especially when using a rotary processor.

My testing procedure:
I mount a 4x5 Stouffer step wedge on a light box and set the camera up to get a roughly 1:1 image with a 210 mm lens. For each development time I expose three films. The first covers zones -III to VIII, the second covers IV to XIV. The third exposure is uniform at about zone V. I tested Tmax 100 and 400 at the same time, so I then could develop 6 sheets, filling all six slots in the Jobo 2521.

By combining two separate exposure of the step wedge I'm able to cover more zones than I'd be able to with a single exposure. The third exposure let's me check overall unifromity and also ensures that for each development run I have a fairly typical ratio of exposed film to developer.

By the way, the zone V exposures all came out looking very unifrom, and with my densitometer I verified that they were uniform to within about 0.03 density units.

Any thoughts or comments would be much appreciated.

[ic-racer]

Because it does not fit all on a single 21 step wedge, I have not recently checked the characteristics near the shoulder. But when I tested T-max the 80s I got some kind of hump then the curve straightened out again before the 'real' shoulder.

You should try to expose it out another 5-10 stops and see what it does.

[gteeter]

Oh, and for what it's worth, here's the plot that I'm extracting development times from based on the curves I measured.

[ic-racer]

Off topic, I'm curious how you are getting 'contrast index' When I see 'contrast index' I think of the plastic 'contrast index' meter that you would put over the H&D curve. It would give a number similar to gammar or slope of the straight part, around 0.6 to 0.7 for the N development.

[Chuck P.]

Recently I've been testing Tmax 100,...............

When you say "test", what is it exactly that you are trying to determine by testing as you have done it? I have several observations but am not sure how to direct them.

[gteeter]

Off topic, I'm curious how you are getting 'contrast index' When I see 'contrast index' I think of the plastic 'contrast index' meter that you would put over the H&D curve. It would give a number similar to gammar or slope of the straight part, around 0.6 to 0.7 for the N development.

I have to apologize--I might be using the term 'contrast index' incorrectly. What I am plotting is basically the slope of the individual curves: D per unit zone. I don't see how you get 0.6-0.7 from my curves...

My apologies again if my terminology is faulty here.

[gteeter]

When you say "test", what is it exactly that you are trying to determine by testing as you have done it? I have several observations but am not sure how to direct them.

The main purpose of the test is to determine development times for different subject brightness ranges--standard sone system stuff. Also there could be a small film speed correction for different development times, although I am less concerned by that as I am typically fairly generous with my exposures to ensure I get adequate shadow detail.

I would prefer to have a baseline development method that will yield a linear characteristic curve all the way through the highlights, and so far I haven't acheieved that with Tmax 100/ Tmax-RS...

[Drew Wiley]

The curve of TMax 100 varies quite a bit with the specific developer. It also has the
tendency to shoulder off a bit abruptly. I have concocted special developers for this
film which give it a very good long straight line; but these are intended for color
separation work in the lab, and I wouldn't consider them appropriate for general
shooting. This is a film which you have to be careful not to overexpose, or you will
run the risk of blocking up the highlights.

[gteeter]

The curve of TMax 100 varies quite a bit with the specific developer. It also has the
tendency to shoulder off a bit abruptly. I have concocted special developers for this
film which give it a very good long straight line; but these are intended for color
separation work in the lab, and I wouldn't consider them appropriate for general
shooting. This is a film which you have to be careful not to overexpose, or you will
run the risk of blocking up the highlights.

Thanks Drew, that's good info to have. Are you aware of a film-developer combo that is more linear? Are there any curves you'd be willing to post?

[Chuck P.]

I'm having trouble uploading from the computer, just won't work, but I could show you TMX/d-76 1:1 curves that are very linear and don't exibit a tendency to shoulder-off til about Zone XII.

CI measurements are not part of traditional ZS stuff. Developing the film to the same contrast range for each planned development time is more to the point. To mean, all times N, +1, +2, -1, -2, compensating, etc...are developed to the same contrast range; one can test for any range they desire, usually a range that very closely approximates the exposure scale of the paper you plan on using. But the idea is to develop the film to your tested range each time. The range is determined by an established lower limit, usually Zone I (0.1 density) and a chosen upper limit, usually Zone VIII (1.3 density) for a range of 1.3 - .1 = 1.2. See Alan Ross's website http://www.alanrossphotography.com/blog/ , cursor down to Zone System Heresy: A Case for Zone IX Calibration. Pretty intersting.