Reciprocity misbehavior.

[PieterB]

This is very interesting. But how about development times?

[gainer]

That last attempt didn't go so well.

I found out so far that when it comes to attachments, 600X800 is not the same as 800X600, that things sometimes go into limbo and that I don't know how to get them out.

[gainer]

OK, there it is, rotated 90 degrees so it would meet the 800X600 (or is it 600X800) pixel requirement. Raw data on top of fitted lines.

[Lee L]

A little got lost in translation to the smaller size. Is the Y-axis labled "Added time in seconds" as opposed to "Adjusted time in seconds", meaning the number on the Y-axis should be added to the original exposure time to get the reciprocity adjusted exposure time?

Thanks,
Lee

Did the math, and the answer appears to be "yes". I won't bother changing my earlier charts, as it seems to me that having the adjusted number is more useful for field work than having the adjustment and doing the addition in the field. But readers comparing the Gainer article chart to the others here should be aware that his graphic tells you how many seconds to add to the base exposure, whereas the other charts posted and linked to from this thread so far give the total _adjusted_ exposure in seconds. That also accounts for the straight lines in Gainer's chart and the slight curvature in the other log scaled charts.

-Lee

[gainer]

This is very interesting. But how about development times?

You must read Howard's report for that information. I presume that the tests were developed to nearly the same contrast index, as that is what Howard would require for his work. It has been a while since I read his paper. We corresponded enough to learn that he plays trumpet and I play oboe and we both are music lovers.

[John McCallum]

I did try it on the corrections Kodak supplied for the old Tri-X and it worked, with a different intercept at 1 second of course.
You only need to find the reciprocity correction for one indicated exposure time, but two would be better. The problem is that these experiments are quite tedious, as Howard Bond pointed out. I think it was several months after that project before he could stand to hear the word "reciprocity".

Ha ha. The fact that the testing by its nature is slow, wouldn't help.

Thanks again. I've been a little unsure of Ilford's published reciprocity correction values for some time. Looking forward to giving your method a try.

Incidentally, it is interesting just how many avid photographers here have metioned they are also musicians - quite a few!

[kaiyen]

A quick question - is the t(c,1) value something one can derive looking at the charts available from ilford, kodak, etc, or something determined through actual testing? In other words, if I wanted to generate graphs of other films, can I do this myself or do I need these values first?

allan

[kaiyen]

oh wait. I see that my question was answerd before. my bad.

[gainer]

Ha ha. The fact that the testing by its nature is slow, wouldn't help.

Thanks again. I've been a little unsure of Ilford's published reciprocity correction values for some time. Looking forward to giving your method a try.

Incidentally, it is interesting just how many avid photographers here have metioned they are also musicians - quite a few!

It has been my experience that there is a correlation between musical and mathematical ability also. Any semipro community symphony orchestra will have its share of mathemeticians, doctors, and other scientists, usually in the string section, but also among the winds.

My sister Miriam Goder got a BS in chemistry and an MA in music and taught for years in the Fine Arts department of Keene College in New Hampshire. My daughter Christine used to keep a math and recorder notebook in grade school, recorder being the musical instrument the Germans call blockeflute (there are some umlauts in there and I may have misspelled it).

[Will S]

It has been my experience that there is a correlation between musical and mathematical ability also.

I spent about 10 years pursuing a PhD and have a MM and an MA from a very prominent school of music.

I can't make heads or tails of your formula.

I do, however, carry around a piece of paper in my wallet that says:

TMAX100 MeteredTime ExposureTime Dev
4 5 N
8 14 N
15 27 N-1/2
30 60 N-1
60 150 N-1
120 360 N-1.5
4min 15min N-2
3min 35min N-3
15min 1hr15min N-3

Which I think I copied from somewhere here. This seems to work. I'm not sure if it graphs to a straight line though. Would this be in line with what has been described so far?

Thanks,

Will