Film Developing Cookbook - Does one really need to overexpose T-grain film by 1-2 stops and pull process to get satisfactory results?

Chuck_P said:

Bill, those green lines indicating my calibrated step densities are precisely why I like that graph sheet so much and I enjoy plotting my curves by hand, it suites me well. I can plot across the sheet very quickly.

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Bill Burk said:

Thanks,

So ChuckP’s graph is correct and any estimate of the illumination at the film plane should make sense working back.

Trusting the film and Delta-X his x-axis at 2.73 (attenuation) is where -2.1 log mcs has fallen upon film.

-2.1 plus 2.73 equals 0.63 log mcs arriving on top of the step wedge at the film plane.

4.27 arithmetic meter candle seconds.

It’s like setting exposure meter at ASA 2 and making the exposure at the indicated reading of the surface the camera is aimed at.

I propose we recommend setting the exposure meter at ASA 2 when making that (in-camera, step wedge in contact with film) test on ISO 100 film.

And set the exposure meter at ASA 8 if making that test on ISO 400 film.

ChuckP can you confirm that you get close to that?

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Mr Bill said:

As I said before, I see the ANSI/ISO film speed ratings as something akin to a stake in the ground, to keep all the players on an even footing. For the b&w pictorial films the ANSI standard, as I recall, simply establishes the amount of light necessary to produce a film "density" of something like 0.10 above the "film base plus fog" when certain conditions have been met. This includes, as I recall, "Photographic daylight" as a light source, and development to some specific contrast value. That's about it. (Aside from some statistical details on the number of samples, and holding conditions before processing, etc.). The required light value is then converted to either an ASA-style or DIN number.

The standard does nothing further... it does not say anything about "correct exposure" for a photograph.

You mention the so-called "sunny 16" rule. It seems like you have a bit of a quarrel with that. However it's not part of the ANSI/ISO standard.



Something that you seem to be largely skipping over is how you, and the others who report on their results, determine what exposure to use. That is, what is their basis for saying that the ASA/ISO film speed is "wrong?" (Or perhaps it is only YOU making the assertion? I dunno.)

I'm guessing that most are using exposure meters. Now, I'm also somewhat familiar with the ANSI exposure meter standard. So I know that this is potentially much more variable than a film speed standard. And there's a bit of a tenuous relationship between this and the film speed standard. The exposure meter standard looks at a somewhat "mid-tone" level of light, whereas the film speed standard is looking at something near "shadow" level. Further, the exposure meter standard allows for the manufacturer to "tweak" the readings somewhat to account for camera-related matters, such as lens flare, etc.

If you were to say that anything was at fault with your exposure issues, I'd say it's much more likely to be related to the meter than to film speed ratings.

All that aside, I don't have any quarrel with your preference for a "thicker" negative. If you like it better, it's your business...your choice. My objection is to your statements that the ISO film speeds are wrong. I think it would be more correct to simply say that you prefer a different EI, Exposure Index, than the ISO film speed.

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DREW WILEY said:

Working with a spot meter is rather different than working with an averaging meter. Grass and asphalt come in all kinds of shades. The same can be said for granite, which is an abundant gray card substitute in many mountain ranges. But ya gotta know which is which. Andesitic diorite can be almost black, while our more common salt and pepper quartz monzonite of the Sierras is often lighter than middle gray. I don't even think about it anymore. I pretty much know what to expect when I aim the meter.

I didn't even bring along the spotmeter yesterday, when I was out practicing with the Nikon and TMax film. And the lighting was rather dramatic. I developed the film this morning, and all the frames were right on. I trust my own experience far more than any formula. But I'll never give up my spot meters.

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