"Full" film speed and Xtol

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I'm aware about finding the true film speed for your own set of circumstances and related aspects of the zone system, my question is really to seek a clarification

For example, I find in my 35mm B&W photography using Delta 400, rating it at 200ASA (or ISO!, whatever)and developed in my given developer at the 400ASA time works best for me.

When commentators say, as they do about Xtol, that a particular developer gives full film speed, does that mean that say for example in my situation, all else remaining equal, if I rate the film at 400ASA and develop it in eg Xtol, I should and get the full range tonality, detail, etc in my highlights and shadow areas?

Please enlighten me and thanks in advance.

-- Frank Alvaro (falvaro@ozemail.com.au), September 28, 1999


I might raise more questions, but think of it this way. The longer you develop, the denser the dark portions of the negative (highlights) get. Think of it as the "adjustable" parameter. The less dense portions (the shadows) aren't affected nearly as much by development time. If you look at a family of curves showing different development times, they pivot (more or less) around the lower portion (the toe) of the curves. Film speed is based on the density at the lower portion of the curve, the shadow area. It's also determined using a specific developer and procedure. So, if a developer "gives full film speed", it really means that it produces the expected shadow density for the film. The highlights are up to you, as any developer will bring them to just about any density, if you adjust the development time. People talk about "full range tonality" or similar statements, and we all think we know what it means, but consider that any film, with any developer, can produce densities that take the printing paper from full black to base white. IMHO, "full range tonality" is a perception that comes from sufficient shadow exposure to give good detail, development to a contast index that matches the subject, certain curve shapes (though I don't know exactly what they are!), and, finally, subject matter lit such that it contains many graduated mid tones. This is all so simple from a technical standpoint- it's just harder than heck to achieve in the real world.

-- Conrad Hoffman (choffman@rpa.net), September 28, 1999.

Just because some one else gets one result, does not mean you can get the same result doing the same thing. The only way you will know for sure is to do the tests. If you are happy with your procedure, why change? Pat

-- pat j. krentz (krentz@cci-29palms.com), September 28, 1999.

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