The Basics of 'Expose for the Shadows - Develop for the Highlights'
One of the first steps that you can take to gaining more control over the results of your photographic endeavors is to try out the 'Expose for the Shadows - Develop for the Highlights' method, which has been around for a very long time. This method requires no special tools or deep understanding of photographic reactions and can give you quite a bit more control over your negatives than using one speed and development time for all lighting conditions. As with any change in your routine, it is best to run a test before taking photographs that are important so that you know what you will be getting from the new routine.
The Concept
The concept behind this method is simple: to have a way to adjust your process (exposure and development) for various lighting conditions such that you can routinely produce negatives that will print easily with a #2 or #2.5 filter, while retaining details in both the highlights and the shadows. It is based on the concept that exposure time determines the density of the shadow areas - longer exposures allow time for the shadow details to register on the film - and development time determines the density of the highlights - shorter development times prevent highlights from losing their details. So basically, you are allowing detail to be recorded in the shadows and preventing over development in the highlights, which results in a negative that is easier to print and which has good detail in both the shadows and the highlights.
Using a set film speed, such as the box film speed or 'personal EI', coupled with a set developing time works well so long as the light conditions at the time of exposure are always the same, but this is not often the case, at least for me. Often I find that light conditions change throughout the day, and this method allows me to adjust my entire process to keep the results very much the same across all different lighting conditions without the need for extensive testing and expensive meters. Always keep in mind, though, that this is simply one method for controlling contrast in your negatives. There are many different systems out there and only you can determine if this is the best choice for you, but I have worked with it for many years and am very happy with the results...
The Practice
Follow these simple guidelines to get started, but don't be afraid to make adjustments based on your results. Your light meter, shutters, film, darkroom timer, etc. may vary from mine so look at your results and make one change at a time until you get the results you are looking for. Nothing special is needed, just use you camera or hand held light meter (no spot meter required) to meter the scene as you normally would.
Flat light:
Conditions - There are no shadows to speak of, if any at all. The light is very flat and shadows areas in the frame are appear similar in value to the value of the mid-range areas of the scene. Brighter areas in which you wish to retain some detail (i.e. Not the sun, but something like the blue clear sky) are not overly bright.
Exposure - Use the box film speed and the standard development times.
'Regular' or Normal light
Conditions - There are shadows, although they are not so deep that you can't still see some detail in them with the naked eye. Highlights are bright, but still also retain some of their details (i.e. The sky is bright and sunny while the shadows are fairly dark).
Exposure - Increase exposure time buy adding one stop to the box film speed rating (i.e. 400 speed film is exposed as 200 speed, or 100 speed is exposed as 50), and cut the development time by a total of around %20-%25.
Strong light
Conditions - Shadows are quite dark and the brightest areas are harshly lit - the sun is shining full on and the light is very strong (enough to cause you to squint).
Exposure - Increase exposure by adding to the film speed a total of 1.3 stops and the cut the development time by a total of around %30-%35.
You can also use these same techniques to increase the contrast of the negative(s). For example, if you want to increase the contrast of a negative, increase the film speed (decreasing the exposure time) and increase the development time.
Roll Film
With roll film, it is not at all uncommon to have a range of lighting conditions on the same roll. With this method you can better control the results when this happens by choosing to develop for the most contrasty lighting conditions on the roll. The negatives that were exposed under the flattest lighting conditions may need a half, or perhaps even a whole, increase in the filter number, but in most cases I have found this to be much better than using the box speed and development times for a roll with mixed lighting conditions.
Sheet Film
With sheet film you have only one lighting condition per negative, so you can develop for the specific conditions for any given negative. This method allows you to get more out of the negative without needing special equipment.
Moving On – The Zone System
I will not get into the Zone System here, but it is the next logical step from this technique for even greater control over your negatives. There are a number of good books on this subject, both in and out of print that you can reference for all the details. The steps outlined above should not be confused with Zone System adjustments like N-1, N+1, etc. Although it uses similar adjustments to exposure and development, the Zone System relies on very controlled film testing coupled with the use of a spot meter to give much more precise control over specific values in the negative.
Further Reading
Here is a list of books that may be of some use to you in understanding the concepts that this method uses. There are many other good books that discuss this technique, but these are the ones that I have personally read and would recommend.
Edge of Darkness by Barry Thornton (ISBN: 0817438157 )
This book goes into more detail than I have about this technique as well as discussing what is actually happening when you follow these steps. In addition, it covers a number of other important film-related topics and is very well written.
Creative Black-And-White Photography: Advanced Camera and Darkroom Techniques by Bernhard J. Suess (ISBN: 1880559889 )
This book has a very nice chart showing the effects of over and under development and exposure, allowing you to see at a glance a comparison of these effects and provides a simple procedure for repeating the exposure/development test with your film/developer combination. It also covers a number of other exposure related concepts that are useful when considering film exposure.
Perfect Exposure from Theory to Practice by Roger Hicks and Frances Schultz (ISBN: 0817453989)
This book goes into great detail all of the theories concerning exposure, including the effects of development. It can get very detailed, but is also not overly difficult to follow. Skip over the parts that you don't understand at first and you will still get a lot out of this book. Then, when you have a better understanding, come back and read it again and you'll get more out of it. This is perhaps the very best book I've yet seen on understanding exposure.