rating film

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I recently read a book called Black and White Photography Masterclass by John Garrett where he suggested rating Iso 100 @ Iso 64, Iso 125 @ Iso 80 and Iso 400 at Iso 320. He said it seems to give better results. I am fairly new to photography, so forgive me if I haven't given you enough information, but if you rate the film at a slower speed, do you have to tell the lab? If I develop it myself, do I have to do anything differently? Thanks, Donna

-- DONNA DEBACCO (magoo4@uswest.net), December 13, 2000

Answers

Donna, some film is able to be pushed up a stop when proccessed. you may want to tell that to the developer and use that for your self. Film that loves being pushed is Ilford hp4 plus and Kodak Tri X

-- Nauman Saghir (Nsaghir@hotmail.com), December 13, 2000.

Donna, Down rating a film gives you better shadow detail and is usually more accurate of the films 'true' speed. I reguarly rate Delta 100 at 80, some films require more exposure to obtain better shadow detail. I also find the published development times to be too high for my tastes. If you process your own b/w films you should make a few trials to achiev negs. that you find fairly easy to print on a normal grade of paper with both shadow and highlight detail. So empty shadows ned more exposure of the film and washed out highlights need less development of the film. Good luck,

-- Trevor Crone (tcrone@gm.dreamcast.com), December 13, 2000.

The reason for doing so is to get better contrast out of your negative. Yes, you must tell the lab, if not your pictures will be slightly overexposed.

-- Marc Leest (mmm@n2photography.com), December 13, 2000.

It is almost certainly the case that the recommendations were made on the basis of obtaining adequate shadow detail, *not* "better contrast." What does "better contrast" mean? More contrast? Less contrast? It depends on the brightness range of the scene you're photographing, combined with your artistic vision.

A lab, unless instructed otherwise, should be developing for normal contrast. Increasing development increases contrast. Since the recommendation was about shadow detail rather than contrast, the lab should not be instructed to alter development.

The statement that improper development would result in overexposed images indicates a lack of awareness about the role of exposure and development on shadow detail and contrast. Adams' "The Negative" is the usual recommendation for learning about these topics.

Ideally, you would test your films in your personal equipment and with your development procedure (see "The Negative") rather than relying on someone else's results.

-- Matthew Hunt (mph@astro.caltech.edu), December 13, 2000.


Film ratings depend on many factors. You need to find your "system speed" this is explained in a very good publication in the "Kodak Workshop Series" titled "Advanced Black-and-White Photography" (KW19). I recommend this book. I was inactive in photography for several years and this publication was the perfect refresher.If you are just starting out I suggest you look into the other books in the series as well. To answer your question, I regularly rate my 400 Delta at 320 and give it a 20% pull in the developer. This is, however, a personal preference. I use a condenser enlarger that works best with a slighty denser, less contrasty neg. My negatives usually print under a no.2 1/2 polymax filter. The other EI ratings mentioned in your question seem about right for my system as well (with the 20% dev. pull). Good Luck. RO

-- Robert Orofino (rorofino@iopener.net), December 13, 2000.


David Kachel once wrote that most zone system photographers, after extensive film testing, end up rating most films at about 1/2 the manufacturers rating. So ISO 400 films are usually rated at EI 200. I've found this to be pretty much what I've found with the 3 or 4 films I've tested and use. The exact rating depends on which developer you use of course.

-- Bob Atkins (bobatkins@hotmail.com), December 13, 2000.

The ISO rating on the film box is what the manufacturer comes up with after testing. The Exposure Index (EI) is what you come up with after testing the film and tailoring exposure and development to suit your taste. It may be faster or slower than the ISO setting recommended on the film box. If you find setting the film speed slower gives you the negatives you like & they print well for you, then do so. Tailoring this EI rating and the processing will give you a 'normal' development time. For you, in one developer, with one agitation method. This isn't pulling or pushing the film, but fine tuning it so your results are what you want and like. The development times from the maker are suggested times, not cast in stone. Your camera, lenses and water used to mix the chemistry are different than that used in film testing by the manufacturers so it makes sense to test a bit and fine tune it all for the best results for you. The big benefit we have with Ilford & The Yellow Peril lies in the consistent high quality of the film they sell us. We can tweak to our hearts content and it is seldom that their products miss the mark of quality results. It is true that many photographers, especially those who take great care with their images from start to finish, end up downrating the film for the sake of greater detail (and control) in the shadows by exposure while tweaking the developing times (and developer dilutions) to control the highlights. You can get away with dense highlights, but shadows that are clear on the negative (clear means NO detail at all) will not give you what the film did not record. "Overexposing" by downrating the film as you find a personal exposure index that works for you can help in assuring good shadow detail where you want it. (as opposed to overexposing & hoping for the best) It is pretty simple in theory but the search for this control has spawned so many books & theories it can make you dizzy. The old photo adage of 'expose for the shadows & develop for the highlights' is a simple way of stating it. At any rate, it works well and only takes a few sheets or rolls of film to get the idea.

-- Dan Smith (shooter@brigham.net), December 14, 2000.

Donna, you casually mention 'the lab.' My concern is that unless you are dealing with a top-notch black and white lab [pretty expensive & rare] chances are very good that you won't get optimum development of your black and white film, no matter what you tell them.

The info in the above posts is very good, but unless you or the lab develop the film in a very controlled environment, it won't make much difference.

chris

-- Christian Harkness (chris.harkness@eudoramail.com), December 14, 2000.


Basic answer, if you re-rate your film for better shadow detail you DO NOT tell the lab to do anything different. What you are doing is adjusting your exposure to the entire chain, which includes development.

I agree that unless you are using C-41 processed B&W film (Kodak TCN400, B&W Select+ or Ilford XP2+) you will not be getting optimum results.

Developing film yourself at home is not hard, nor does it take a lot of equipment. You don't need a darkroom, just a dark place to load the film onto the reels and into the tank. This can be a changing bag, a closet, a bathroom, or any place where you can get it really dark.

Check some of the other threads about this.

-- Terry Carraway (TCarraway@compuserve.com), December 14, 2000.


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