You are over analyzing.
You are over analyzing.
I guess I do tend to over analyze. And some of you are saying, "What do you mean 'guess'"? :)
But that's better than the alternative. This testing is teaching me a great deal about variations in film, and how to test them. I didn't know that films varied so much. For that reason, I now realize that a developer needs to be tested with every film being made by Ilford, Kodak and Fuji. And it wouldn't hurt to include Fomapan as well.
About shifting characteristic curves: PE, you lost me there (and as I read it you lost Mark as well). Why would one shift the curves except for comparing contrast? Shifting a curve left would hide the fact that it takes more light to create discernible density, wouldn't it?
While shifting could show a better correlation between two processes, I think most of us would view a loss of film speed to be a disadvantage.
As an aside, I wonder if anyone could offer an opinion on this: I'm interested in mixing up the simple formula in post 355, on the spot, and without propylene glycol. How long would it last after mixing? I'm thinking of a big day of film development, mixing the dev in the morning and going all day.
Also, since the vendor of my sodium metaborate (Vanbar in Melbourne Australia) have not been able to tell me which level of hydration it is, and since I don't own a pH meter, would good pH papers be enough to get the amount of metaborate right? I envisage mixing it assuming the least level of hydration then adding metaborate if pH is too low. I have some Microfine pH paper for the range 7.9 to 9.7.
Shifting the curves is indeed helpful because you normalize for speed. For example I know if I rate Delta 100 at EI 64 and TMX at EI 80 and develop them both in XTOL 1+1, the curve shape is nearly identical up to the areas above zone X-XI where Delta has slightly higher highlight contrast than TMX.
Shifting curves (on 2 sheets of paper and over an illuminator) will show you many things.
1. The shift on the X axis will allow you to read the precise speed difference at mid scale, thus giving you the speed difference in Log E or stops.
2. The shift will show you absolute contrast differences, toe differences and shoulder differences.
When we ran series like this, we plotted each curve on one sheet of paper each. Then we shifted these sheets on a light table to align them in a way that would show the desired characteristic against a norm.
So, for example, Mark has stated that one sample has a softer toe than the other one, but IIRC, the opposite was true. You only see this if you line up the mid scales of those curves.
Try it, you will see what I mean.
It's true that the Contrast Index (done Kodak's way) of TMX is 0.04 higher, but I doubt that would account for this difference in curve-shapes. Also, Zonies would say these have about the same CI because they measure from Zone I to Zone IX, which goes out to X=0.3 where the curves converge. BTW, this graph is why I mentioned that Delta 100 has a longer toe. Can you post the curves you got for these? What CI are you getting? I'm wondering if your graphs are closer to my TMX or Delta 100 graphs. I'm also wondering if I seriously overdeveloped my TMX.
Tmax-400 (TMY2) is acting weird again. It has an odd two-slope density-curve with both XTOL and D316. But all other films are behaving fine.
You might remember almost a year ago, that TMY2 was giving me thin results with both XTOL and home-brews. I discovered that presoaking improved density. That's still true (see graph below), but TMY2 is acting odd even with a presoak. Here are the curves:
XTOL and D316 (with presoak) are about the same, having two slopes with an inflexion at X=-1.3, and with slightly stronger highlights in D316. But not presoaking loses much density (green curve).
Other odd symptoms include:
- The fixer used to pour out magenta. Now it's clear.
- The early wash-water used to pour out magenta. Now it's clear.
- The negatives have a strong magenta cast. Even washing for 30 minutes didn't help. Even warming some wash water to just over 20C didn't help.
The batch-number of TMY2 has changed. It's now 0167; for months it's been 0166.
For comparison, here's a roll of Tri-X developed two days later. It has a perfect near-straight-line curve:
All other films are behaving okay also. For example, here's a roll of FP4+ developed the same day as the Tri-X:
I'm reluctant to blame Kodak, but the batch-number has changed and suddenly these issues appeared. OTOH, it is winter, and my wash-water is cooler at 18C which could make it harder to clear the magenta dye. But that wouldn't reduce density. Or would it?
The "broken" curve suggests that Kodak is having trouble blending emulsions. That is usually the result of what you see in the first curve Mark.
There are those that praise such "saggy" curves. They say it gives a good tone scale to the print. I do not agree.