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.

[gteeter]

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.

I will check out that link--thanks.

My goal is basically what you describe. Aside from issues with the shape of the characterisitc curves, with my testing procedure I have determined the development times that will allow me to develop my negatives from N-3 to N+3 (see the second plot I uploaded), based on the subject brightness range for a particular scene, to acheive a range of densities on the negative of about 1.5. I determined that this was a good target based on separate tests I did on Ilford MGIV FB paper.

For silver-based printing, I don't intend to develop any negatives density ranges higher than about 1.5. But at some point I might try my hand at Pt/Pd printing, and I understand that more contrast is needed in this case. I think my tests will help me develop good negatives in that situation too.

Again--my terminology is probably at fault for the confusion here... I read many of the common books on this topic, but many years ago. And i have adopted my own procdures based on what made the most sense to me at the time.

[ic-racer]

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.

I think I see. You are using 1 for each zone instead of 0.3 when doing the slope calculation, right?

[Chuck P.]

I determined that this was a good target based on separate tests I did on Ilford MGIV FB paper.

That's the paper I use too, but when I did my testing I used the traditional Zone VIII calibration of 1.3 for "normal" dev----according to Ross, with that calibration, if planning -2 development (i.e., a Zone X luminance developed to a Zone VIII negative density) that may make it hard to get paper base white from the paper, but I haven't had that experience, at least that I can determine anyway. I look forward to seeing all your results.

[gteeter]

That's the paper I use too, but when I did my testing I used the traditional Zone VIII calibration of 1.3 for "normal" dev----according to Ross, with that calibration, if planning -2 development (i.e., a Zone X luminance developed to a Zone VIII negative density) that may make it hard to get paper base white from the paper, but I haven't had that experience, at least that I can determine anyway. I look forward to seeing all your results.


Here are my paper test results. One very important point--I measured transmission densities on these prints rather than reflection densities. (I'm in the market far a reflection densitometer but haven't picked one up yet...)

The actual curves should be taken with a grain of salt, obviously, because of how I measured them. Nevertheless, the results are consistent with my visual impressions of the prints in terms of which steps show paper white vs. Dmax, so in that sense I think they are useful for determining how negative densities will map into paper densities.

Based on these plots I decided that a negative density range of 1.5 would give me a full-scale print at around grade 2, but I haven't tested that with actual photographs yet, so that might well turn out to be too contrasty. If I find that I am making a lot of prints at grades 0 -1 and few at grades 3-4 I'll adjust accordingly. But hopefully this gets me in the ball park.

[sanking]

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.





I was about to comment that all of the developers that I have used for Tmax-100, including D76 1:1, have given very linear results.

Sandy King

[gteeter]

I was about to comment that all of the developers that I have used for Tmax-100, including D76 1:1, have given very linear results.

Sandy King


Sandy, is Tmax-RS one of the developers you've used with Tmax 100?

Perhaps I've been barking up the wrong tree--I need to try D-76 at some point.

[sanking]

Sandy, is Tmax-RS one of the developers you've used with Tmax 100?

Perhaps I've been barking up the wrong tree--I need to try D-76 at some point.

I have used Tmax-RS but it did not seem to offer anything over D76 1:1 and I never tested it.

Developers I have used and tested for curves are Xtol 1:2, D76 1:1, Pyrocat 1:1:100. I got very linear results with all three.

Sandy King

[Drew Wiley]

I've plotted plenty of curves with this film, but these have mainly been for technical
lab use. My developers use toe-cutters, so are not something I'd recommend for
general use, since there would be absolutely no forgiveness of exposure error, and
would reduce speed. These are intended for extremely precise exposure in film
registration equipment under an electronic additive enlarger. However, I have used
TM100 for commercial work, portraiture, even landscape, with excellent results in
a number of developers. My favorite is PMK. This film has good shadow separation.
But if you need a more linear response in the highlights, the new TMY400 is much
better. It will give you a straighter line in ordinary developers. For landscape, I
gave up on TM100 because it had so little edge effect. It could hold a lot of detail,
but never appeared crisp in the print. Here again, the 400-speed equivalent seems
much better.

[Jan Pedersen]

Glenn, No help with curves from here but i noted that you are thinking about using TMax100 for Pt/Pd printing. TMax100 is perhaps the last choice film for this purpose since it has a UV blocking layer incorporated which make is almost impossible to use for UV exposure which is required for Pt/Pd printing.

[gteeter]

Thanks everyone for the helpful responses.

I exposed and developed Tmax 400 in parallel with the TMax 100 that I plotted in this post, I just haven't gotten around to measuring the densities of those negs and plotting them. I'll do that and see how the two films compare.

Jan--thanks especially for alerting me to the UV blocking layer in this film. I can only imagine how much frustration that would have caused me if I tried to use this film for Pt/Pd printing!

[Chuck P.]

After many tries, finally got an attachment to work. I wanted to show you the TMX/D-76 1:1 curves---you can see the linearity of these, and although, it is not shown here, they'll begin to schoulder off between Zones XI and XII. If your're looking for a more linear curve with TMX than what you're getting, I would suggest d-76 1:1. However, I did not expose my step wedge the way you did, so your results may differ and I used a Combi-Plan tank and not a rotary processor, but I don't believe that will make a difference, IDK.

[Stephen Benskin]

Glenn,

T-Max 100 is a very linear film. Most of the time when you see strange rises or dips in a curve it is because of some experimental error. Don't worry about the results of the test and just do another.

I'm curious about the y-axis in your development time / contrast index graph. The numbers seem to be much too low for CI or negative density range values. Also, could you explain your developmental aims of your minuses, normal, and pluses. Did you also say that a density range of 1.50 was your desired negative density range? That seems rather high for silver printing.

[gteeter]

Hi Stephen,

I attempted to respond earlier, but it appears that post got lost in the ether. I'll try again...


T-Max 100 is a very linear film. Most of the time when you see strange rises or dips in a curve it is because of some experimental error. Don't worry about the results of the test and just do another.


In fact I have performed many more tests than shown in the plots I posted--these are actually the most linear curves I've been able to generate. I suspect that uneven development in the Jobo 2521 reel/tank system could be playing a role here, but I have developed 'blank' zone-V exposures with each set of characterisitc curve negatives, and these are coming out very uniform. For example, I get the following densities for the 'blank' developed with the 20 min. negs that I plotted: center, D= 0.76; four corners D = 0.75, 0.76, 0.77, 0.77. While that is not perfectly uniform, I don't think it can account for the nonlinearity in my curves at higher development times...

The conditions that seem to minimize the nonlinearities include: lower temperature (20C vs. 24C); higher dilution (1:9 vs. 1:5); and minimal agitation (speed 0 on Jobo motor knob).

Note also that at 8 min. my curve is pretty linear up to about zone X, which is fine...




I'm curious about the y-axis in your development time / contrast index graph. The numbers seem to be much too low for CI or negative density range values. Also, could you explain your developmental aims of your minuses, normal, and pluses. Did you also say that a density range of 1.50 was your desired negative density range? That seems rather high for silver printing.

Others have commented on this--I think the issue is that I am plotting my characterisitc curves vs. 'Zone' (log base 2) rather than the standard log base 10. If I did everything in log base 10 I think my CIs would be closer to what everyone is expecting. Log base 2 is just more intuitive for me when thinking about exposures...

My goal with these tests is to determine the development times appropriate for N-3 thru N+3 development. If you examine the second plot I posted (with the erroneously labeled CIs) You will see that I plotted the slopes (red circles) I extracted from my curves as a function of development. These happen to fall on a straight line. From this line I have empirically interpolated the development times that will give me N-3 thru N+3 development (the green points). This procedure is probably different than that used by most people, but in the end I think it gets me to the same result.

Other have also comented that 1.5 might be too high a contrast range for silver printing. But I determined this was good target based on tests I did on Ilford MGIV FB paper describe previously in this thread. Note that I am using a diffusion enlarger head, which will require somewhat higher contrast negs than a condensor head. And if it turns out that my negs are consistently too contrasty I will adjust accordingly.