Tri-X 400 @ ISO 320 now developing with less density ??? baffled.

Hi, I am a little baffled . I already had my Trix-400 rated at ISO 320 giving me a good density in zone I of about 0.07 ranging to 0.11 so I was happily shooting it at ISO 320 . Lately I decided to retest the speed of the film for whatever reason. I was surprised to see Zone I now measuring at 0.05 . I repeated the test again with same results. Then I tried a third time very carefully again just in case not to introduce any possible variables. Now I am getting density of 0.02 to 0.03 in Zone I with exact same methodology. I use an 18% middle gray card shot in open shade occupying the whole frame in out of focus. (I am using Ansel's book methodology exactly as described). I processed using the same processing times, developer D76 and dilution 1:1 @ 68F as I always do and had already down. I would have to rate the film now at like ISO 200 to get close to density 0.10 as expected, but that will shoot the higher zones much higher. What gives ? what could possibly have happened.??? I must note that I am getting the same results with two different cameras of the same kind. Both are Canon Elan 7E. In other words, I don't think it should be the camera because both are giving me the same density at the same time. I re-calibrated my densitometer and metered the calibration sheet with perfect measures exactly as expected. So it shouldn't be the densitometer I think. I don't understand.

Are you using the same batch of developer? Perhaps it is failing?

Originally that is what I thought, so I waited until mixing a fresh batch. The last test was made with a fresh mixed batch of D76. :-(

If you are certain your present tests are without flaw then your prior tests have been flawed. Too bad you can't repeat them being more careful...wait, you just did repeat them and you got your new answer.

Has your gray card changed over time?

What about Shutter speed issues? Just trying to think outside the box.
~M

maybe your agitation method changed
or your developer was a cooler temperature

It's not unusual to find Ansel Adam's speed test results for 400 speed film is EI 200.

Before you come to a firm conclusion... Have you done development times tests?

batch

Is your Tri-X all from the same batch or are you now shooting some film that you recently purchased?

snapguy said:

Is your Tri-X all from the same batch or are you now shooting some film that you recently purchased?

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no, the Tri-X is not from the same batch. But I wouldn't want to think that the film would change so much from one batch to another. That wouldn't make sense unless one batch is damaged.

Bill Burk said:

It's not unusual to find Ansel Adam's speed test results for 400 speed film is EI 200.

Before you come to a firm conclusion... Have you done development times tests?

Click to expand...

Yes, it bothers me because I had all the other zones pretty much in the right place from V to VIII at 9:45 Dilution 1:1 and agitation per Kodak recommendation. Agitation variation or even time should not change zone I as other suggests. that's why I did not worry much about those two variables. Speed test is only affected by exposure. right ? The only thing I can possibly think of is that I do not remember if the original test was performed in the same light conditions as the more recent tests. Would that explain my variation ? I know densitometer was not the problem because the film was measured by me and by another APUGer and we both had the same results. So what I stated above is the only thing I can think of.

im sorry to ask this, and i ask this as someone who DOES NOT use the zone system
to expose film ... it isn't that i don't understand the methods &c, i just don't use it ...
is there any way you can just, well, expose some film and not worry about the variation
in your densitometer reading?

while i am guessing, it might be a terrible thing for me to suggest .. but it might not make that much of a difference
especially since you are using 35mm film, and you won't have trouble or expense to bracket an exposure or 2.
this whole endless test thing is what made me stray from the ZS, now i just keep in mind what the light is like
i expose my film and develop it and it turns out as good or bad as i expected.

good luck with your further tests, exposures and prints !
john

It did not answear your question, but I use the same time, dilution, agitation and temperatur like you and my film speed is something between ISO 160 and ISO 200

lhalcong,

When I first tested film I made such a mistake that my 400 speed film rated at 64. It was a complete test by the book (Minor White) with a few minor mixups (like not keeping good track of development minutes). But the graphs looked reasonable so I used them on an important trip. Shooting 400 speed film at 64 didn't cause any problem. The negatives from that trip are amazing.

Later I learned what my problem was. I had mounted an SLR in front of a 4x5 camera to get accurate shutter speeds. I didn't realize that the rigging caused vignetting on the Zone I strips.

But when I got back into testing, I found my speeds held consistent for a very long time... Until I tried some different films. Then I started questioning my methods and speed benchmarks (because 32 and 400 films weren't 3 2/3 stop apart as expected)... Now I am finding consistency to a certain degree but still see occasional differences of 2/3 stop speed from what I expect. I'm trying to keep my methods consistent, but I do get an occasional wild result.

I think you improved your methods over time and now you have good results.

Or your methods might be a little bit out of control (who can say theirs aren't? I can't).

Or you have not changed anything except the spectral characteristics of the gray card and it bears a complex relationship to the meter and film response which causes your earlier tests to be different.

I believe the 400 speed test results saying 200 for Zone System purposes is an expected outcome, so I think this is the test to run with.

jnanian,

Someday I'll be able to explain the allure of calling your shots...

lhalcong said:

no, the Tri-X is not from the same batch. But I wouldn't want to think that the film would change so much from one batch to another. That wouldn't make sense unless one batch is damaged.

Click to expand...

Or your sample cooked in storage...
Has the base density changed?

Could the angle of the film plane to the gray card have changed from the meter reading to the actual exposure?

Rick Jones said:

Could the angle of the film plane to the gray card have changed from the meter reading to the actual exposure?

Click to expand...

This is the most likely possibility for earlier tests coming back that the film is more sensitive... Because if there was glare the camera lens saw but the light meter didn't see due to a different angle... The light meter would say it's darker, recommend more exposure, the film would get more exposure and respond more to that exposure... and it would "seem" that the film was more sensitive.

Now it seems lhalcong you are getting expected "half box speed"... so maybe now you are positioning the gray card, metering and shooting it more correctly than before.

If you used your through-the-lens in-camera meter, that bet is off and I'd have to go back to the spectral characteristics theory...