Newbie questions (Pt. II)

[Colin Corneau]

More often than not, I've noticed photographers basing their exposure on EI's less than a film's posted speeds...HP5 @ 320, TMX100 @ 50, etc etc.

Is this purely a matter of experimentation, and seeing results based on exposure and development being tweaked? It seems more commonplace than simply a few photographers' personal preference.

It's all a bit bewildering as I start out on a (hopefully long) path in LF shooting.

To me, at first blush, if a film says 100, I expose at 100 and start out developing it at the recommended times and developers. But, that doesn't seem to be the case and I'd like to know why as I try make my way through this silver jungle.

Many thanks
Colin

[bdial]

The box speed is based on specifically defined tests in controlled situations. If we all did our pictures in the same situation, using the same developers and processing it for the same time, our film speed would be the same as the manufacture's.
But that isn't the real-world situation, so the box speed is a starting point that varies with the lighting present in the scene, the photographer's meter technique, the particular characteristics of the camera and lens in use, and finally the development procedures he uses.
There are a number of descriptions and methods for determining the film speed of a particular emulsion/developer combination that are described here and in other sources. Doing that testing allows you to tailor the number you use for setting your meter to your techniques and equipment.
That said, there is nothing wrong with starting where you've started, that's the point of the published numbers.

[Rick Jones]

Starting with the manufacturer's rating and development times makes perfect sense. That said, it is very important to be guided by results. For example, I print with a condenser enlarger requiring me to reduce most manufacturer's development times in order to keep contrast under control. A result of that is reduced film speed. The amount of shadow detail you retain in your negatives is controlled to a large extent by how you rate your film but also by how you use your meter. Again, results should guide you. If you prefer fully detailed, open shadows you may have to lower your film ratings. If, on the other hand, you go for the graphic look with dark empty shadows you will probably be raising your film ratings. So as they say exposure controls the shadows and development controls the contrast.

[Colin Corneau]

One of the reasons I ask is I'm starting to shoot a project that is, for the most part, under similar lighting for all the shots (inside a warehouse, relatively flat lighting/flourescent lit and generally evenly lit - almost dull) and I'd like to get the most out of the film I'm using.

I'll look for those threads on determining a film/developer combo, but I'm certainly not above someone posting a link.

[srs5694]

I'll look for those threads on determining a film/developer combo, but I'm certainly not above someone posting a link.

One article (in two parts) that describes how to determine the optimal speed and development time for a particular film is:

http://www.halfhill.com/speed1.html
http://www.halfhill.com/speed2.html

Another popular approach, which is most often used by large format photographers, is the Zone System. This involves careful metering of specific parts of a scene and adjusting the development time for each shot. If you're shooting large format, it might be worth looking into the Zone System in more detail. I shoot 35mm and medium format, so I've not looked into the Zone System in any detail, but since you mention you're embarking on large format shooting, you might want to research it. A Web search turned up a lot of hits, and I'm sure it's described in a lot of books, but I don't have any specific suggestions beyond that.

[bdial]

Ansel Adams basic photography series, The Negative would be a good place for learning the zone system.
For more contemporary info, try Bruce Barlow's site and writings at http://www.circleofthesunproductions.com/
Bruce has a book with testing procedures, and a film test kit, that will help you along.