The best curve didn't have numbers on the X-axis, which would have been great for calibrating log-E.
The other was a group of six or so curves, all superimposed, forming a band in which you could see variations from each other. It showed that Kodak's manufacturing was staying within reasonably tight tolerances, but that's still not what we want for comparing with our own work.
Bottom line: I have no curves to post that would help us with our own measurements. But I can post what I got if you're still interested.
Hi Mark - if it isn't too much trouble to post them I'd still be curious to see them.
I would also be curious to see them, Mark. Thank you!
Originally Posted by Michael R 1974
That's two requests, and others are probably interested too, so here goes.
The curves below show the lower- and upper-contrasts for all recent batches of TMY2. It's clear that nothing has changed in the last few months:
And here are the curves of recent batches. They all fall within a reasonably close band, so once again, no problem:
As a result of my query, Kodak pulled some sample films from storage, exposed and developed them, and plotted the above curves. I was hoping they would include samples purchased from the open market, but I'm guessing the curves above convinced them that everything is fine.
Mark/PE - what increments do you suppose the tick marks are on the log exposure axis?
While the curves all fall within a resonably close band, at least two of them appear to show the type of curve I got - ie a slight dip and then an increase in contrast (at around the same densities I observed).
Again, nothing to worry about from a user standpoint, but I'm glad you posed these because they show us there will always be some variation in manufacturing - however small. Even the base fog density seems to move around slightly, and as long as Kodak is ok with it, I'm ok with it.
I think this is important because there are people who try to calibrate their home testing to the n'th degree of precision, and they'd also call a slight change in curve shape catastrophic. These curves show that even disregarding all the variables and errors involved in home processing, there will still be some small degree of variability inherent in the manufacturing process. We might never know for sure on any given day precisely which curve we have, but they are all close enough.
Thanks for posting these, Mark!
The curves do not resemble those that we got in-house. These are quite heavily "sanitized". And, they do not really help Mark in his problem. You see, this might be a keeping problem on the shelf or during shipping, and EK does do keeping tests. Just pulling a sample does not help.
I have a composite curve I am posting here (Thanks to APUG member Terry Holisinger for the fine image). This superimposes a film, paper and print curve. The relative horizontal displacements are not correct.
The X axis is LogE and each number represents 0.15 log E. The Y axis is density.
This would have exposure data on it that would give us the absolute speed of the curve. This is related to the settings on the 1B sensitometer used for exposing the material.
Also, we use wider paper for film, as the density extends to 3.0 and as you see, it goes off the right side.
@Michael R: Assuming the slope is about .58, then I think the little horizontal ticks would be 0.2 log-E units each.
@PE: Sanitized? That didn't occur to me. There's no question that Michael and I both got upswept curves, but not severe enough to hurt folks much. Just a little more burning needed. Kodak didn't see that, and it makes me wonder what's going on. And the recent report of felt-trap dust outside and inside 35mm canisters makes me wonder some more. I'm glad I tuned the Mocon developer to work well with Ilford films, particularly Delta 400.
Sanitized does not mean that the curves were changed, but merely that information such as speed and exposure were removed. No developer or development time is evident, and there is no comment on keeping from EK. Bad keeping can do strange things.
That's the kind of detailed curve I was hoping (perhaps wishing) they'd have sent Mark. Oh well.
I still think at least two of the curves they provided show the same type of shape Mark and I observed, but it seems they are within spec.