Help reading development charts

[sterioma]

Hello everybody,

this might sound like a dumb question, but here it is anyway.

I am making a basic speed test know how to best rate Tri-X with my equipment.
Suppose that after the test I find out that I should rate Tri-X as 200 ASA.

Now, how do I read a development chart for Tri-X? Should I follow the instructions for Tri-X at E.I. 200?

I am a bit confused about how the "personal" rating of the film relates to pull/push processing.

[rogueish]

If you expose TX400 at a 200 rating, you would indeed develop at a 200 rating. Once you are comfortable with that (ie your negs come out well and your happy) you can start experimenting by adjusting the time (say 6.5 mins instead of 7minutes).
Just in case, have you seen the http://www.digitaltruth.com/devchart.html
And has been said before "The only dumb question is the one unasked."

[bobfowler]

Part of the test for your effective speed is determined by your developing technique. I would start with the suggested development times and make a seris of exoposures of the same scene at various EI's. Find the negative that comes closest to your desired result and make development adjustments from there. A lot will depend on the brightness range of the scene and your metering technique.

[titrisol]

I concurr with bob.
You have to decide what the standard development procedure is and then shoot a test roll, bracketing every 1/2 stop or so. Examine the negatives and then decide which is YOUR speed for the film.

[sterioma]

I have started with TriX rated at 400 as per manufacturer recommendation. I have made a few bracketing exposures (a few also around Zone I as recommended by Ansel Adams).

I will then develop using the 400 E.I. development times for my film/developer combo (TriX/Rodinal in this case).

Now, suppose that I like the results of 1 stop more better. This would lead me to rate the film at 200.

If I got your points, bob and titrisol, I shouldn't refer to the development charts anymore but use that development time as a starting point and make further adjustments from there. Is it so?

[lee]

I would be tempted to use the EI of 200 and then use the development chart and subtract maybe 20% from the published time. This is good practice with 35mm film.


lee\c

[sterioma]

I would be tempted to use the EI of 200 and then use the development chart and subtract maybe 20% from the published time. This is good practice with 35mm film.

Lee, would you be using the suggested development time for E.I. 200, or just shoot at 200 and use the development time for 400?

Also, why do you say that shortening the development time is a good practice for 35mm? Is it something related to the grain or something else?

I have just started developing my own BW and I am already fascinated by how many things I have to try (and learn!)

[David A. Goldfarb]

If you develop the film for some time (say, the manufacturer's recommendation for EI 400) and discover that the exposures that give you sufficient shadow detail are at EI 200, then in the future rate the film at EI 200 and develop for the time you used in the test, and ignore what the chart says about film speed.

Film speed is about shadow detail. Development time is about contrast.

If your negs are too contrasty at the time you're using, decrease the development time, and if they are flat, then increase the time, but the speed will not change significantly.

With the same film/developer combination, you can change developing time and the film speed will be about the same, but the contrast will be different. Even though manufacturers' film development charts say that you can increase film speed by increasing development time, this is in general a myth, if you measure film speed in terms of shadow detail. To get a real increase in speed with a particular film, you usually need to use a different developer formula or a technique like stand development.

[davet]

David Goldfarb has got it right. You need to decouple exposure from development time. Exposure sets shadow density, development controls slope (contrast). It may be that you find shooting at 200 and developing "normally" (recommended for 400) works for you. It may be that you need to pull 20% (probably a good place to start) or more, especially if you shoot high contrast scenes and want separation from shadows to highlights. It may be that you want to add development time, if you like the high contrast look. It will likely be that you have no single development time for this film. Consider exposure and development two independent controls, and experiment!

[lee]

Lee, would you be using the suggested development time for E.I. 200, or just shoot at 200 and use the development time for 400?

Also, why do you say that shortening the development time is a good practice for 35mm? Is it something related to the grain or something else?

I have just started developing my own BW and I am already fascinated by how many things I have to try (and learn!)

I would use the 400 time. Shortening the development time will help reduce the contrast somewhat and it will help with the grain to a certain extent. IMO, most of the times are just a little too long for normal photography. Plus, it gives you a place to start. Shooting the film at half of the box speed will give you more shadow detail and reducing the development by 20% should help tame the highlights.

Experiment and have fun,

lee\c