Shooting at lower than rated ASA?

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Can anyone tell me the results of setting your ASA lower than your films rating? I am thinking of CN 400 @ 300 or @200ASA.

-- Thomas Horan (fishman57@aol.com), July 05, 1998

Answers

ASA or ISO as the current standard maybe, is a speed rating depending on a certain amount of developing. Many Black and White photographers over time have found that a more pleasing array of tones can be created by lowering the film speed and the amount of development also. By using a lower ISO setting you are increasing the over all density of the negative which will have the effect of increasing your shadow detail, a desirable thing as long as it is not done to an extreme.

-- Jeff White (zonie@computer-concepts.com), July 05, 1998.

For the best treatment of this subject, read Ansel Adam's "The Negative".

That said, I've had fine results with pulling film. What do you do for exposure? A bit over, half to one stop. (OK, so it isn't B&W: Kodak E100S gave me great results with +1 exposure, N-1 development)

Here's the funny thing with film: Film speed is set at the factory. What development does is control contrast. Normal exposure and normal development gives you a "normal" negative. Over exposure and under development gives you a "normal" negative. Under exposure and over development gives you a "normal" negative.

So what's the difference? Contrast. The +1 exposure, N-1 development will result in a lower contrast. The -1 exposure, N+1 development gives you an increase of contrast. Expiriment. Like everybody here says, what works for one person may not work for another, literally or figuratively.

-- Brian C. Miller (a-bcmill@exchange.microsoft.com), July 06, 1998.


Thomas,

Overexposing T400 CN will actually produce even finer-grained images --to a certain extent. Exposed at an EI of 400, T400 CN is as fine-grained as T-Max 100. Slight benefits can be seen by overexposure of no more than 3 stops. This film has an incredible amount of exposure latitude.

Michael D. D'Avignon - KODAK Professional

-- Michael D. D'Avignon - KODAK Professional (l638708@mso.kodak.com), July 07, 1998.


You need to determine your "system speed", the manufacturers film index is a startying point. I shoot 35mm and print on a condenser enlarger. Therefore I overexpose my negatives by about 20% and underdevelop by 20%. For example I expose my Tmax 400 at 320 ei and develop it in Tmax dev for 5 min at 75 deg f. You need to developyour own system speed. Kodak has a book called (I believe) Advanced Black and White Techniques, that explains the mechanics of attaining you personal "system speed".

-- Robert Orofino (www.rorofino@uscgelc.gov), July 13, 1998.

I took an advanced B&W class once, in which we measured the actual speed of our film, using a densitometer. Making the measurements took a long time and was a pain in the butt, and my results were not noticeably different than what I'd been doing before (namely, shooting Tri-X at 400; my measurements told me to shoot at 125 and develop 15% less).

There was nothing *wrong* with the results, mind you; they just weren't better enough to justify the two-stop loss of speed, and the hassle of remembering to underdevelop.

For what it's worth, nowadays I shoot Tri-X at 800, and process normally. I'm happy with the results.

-- Eric Hanchrow (erich@microsoft.com), July 29, 1998.



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