Exposure Methods
The following are some methods of making exposures which generally try to improve your chances of getting that most excellent image. Which you use, or which combination you use, depends on what you are trying to achieve visually, as well as your personal bent. It's worth trying each. You’ll find your own personal method only through doing, so get at it. In no particular order:
Exposing for Shadows
This is a method that fully states “expose for shadows, print for highlights”". The theory is that if you get shadow detail, you can print it, as well as the highlights. If you don’t record the shadow detail on the film, you can’t print it. By metering and exposing for the shadow areas of the scene, you will render them middle grey on the film, assuring good detail. Your negatives will be nice and dense. The danger of this method is in a contrasty scene, the highlights will get blown out.
Bracketing
Bracketing is kind of the shotgun method applied to exposure. It’s done by making a series of exposures of the same subject, at settings that yield less and more exposure than the meter reading. A typical series might be five exposures: 1 stop under, 1/2 stop under, at the reading, 1/2 stop over, 1 stop over. Or five exposures using full stops: 2 under, 1 under, on, 1 over, 2 over. The amount of bracketing, and the increments used are up to you, of course.
What you will see after processing your film is a series of the image, from (probably) rather underexposed to (again, probably) rather overexposed. It may seem a waste of film, but until and unless your metering is tuned to your image, one of the alternate exposures may be better than the one taken at the meter reading. The series will give you a set of exposures differing in density. Bracketing by half or third stops will give you more discrete differences to choose from.
Of concern with bracketing is which control you alter, shutter speed or aperture. If motion is not a concern, it makes more sense to alter the shutter speed, so that you maintain the same depth of field, and conversely, if motion is of concern, alter the aperture.
This leads to another method of bracketing, which concentrates on image rather than negative density. You may want to bracket a still life, say, altering the aperture, and keeping the same exposure value by also altering the shutter speed. You will get a series of exposures of the same density, but going from shallow to long depth of field. The same can be done with shutter speed and apparent motion.
Placement
Placement is a bit more involved than bracketing, but once gotten used to, is an easy method of improving your negatives. Placement employs the dictum of exposing for shadow areas and printing for highlights.
The first step in placement is determining the significant shadow area(s) of the scene. Fill the viewfinder with this area, take a meter reading.
Then, using the settings from that reading, recompose your scene and take the photograph.
The resulting negative will render the shadows as middle grey, with full detail. Now this is a good thing, but it may present something of a problem. With the shadow areas at middle grey, there’s a good chance that the highlights will be too dense. So we move to a refinement. Without delving too far into the Zone System, where we want the shadow details to be tonally is two stops darker than middle grey (dark with detail, or Zone III). To achieve this, we need to take the original reading (which places the shadows at middle grey) and set the camera for two stops less exposure, then recompose at take the photograph at the new settings. This underexposes the shadows, making them thinner in the negative (and darker in the print), while retaining detail.
By the numbers: the shadow details meter at 1/30th @ ƒ8. To place them at the correct tone, the adjusted exposure would be two stops less, or 1/125th @ ƒ8. Just takes a little practice.
Adjusting ASA
This is less a method than a correction. There are a couple of reason to change the ASA setting of a particular film from the manufacturer’s recommendation. The first is consistent over- or under-exposure. If you expose several rolls of film, and they all come out consistently too thin, and you are pretty certain you are doing everything correctly, you can change the ASA setting to a lower rating for that film. That will tell your meter that you are using a slower film, and the meter will give you combinations that will yield more exposure. If you change the ASA on 400 ASA (rated) film to 200, you will double your exposures. Likewise, changing to 800 ASA with 400 rated film will cut your exposures in half.
A technique called pushing film involves just this. In low light conditions, one might rate 400 ASA film at, say, 3200. This will give you, in effect, 3 extra stops to play with. It will also grossly underexpose the film, so to compensate, you need to overdevelop the film. A lot. This will generally give you printable negatives, but they will be very grainy and very contrasty. This method really should only be used for effect, rather than as a substitute for using a faster film or getting more light on the subject.
ƒ/16 Rule
The ƒ/16 rule is a rule-of -thumb guide for exposing film without using a meter, and a good guide to keep in mind when you are metering. Briefly stated, in direct (bright) sunlight with distinct shadows, use a setting of ƒ/16 at the inverse of the film speed. If you are using 125 ASA film, your shutter speed would be 1/125, for 400 ASA use either 1/500 or 1/250 (or both). The chart below shows some adjustments.
| ƒ/16 Rule (using 125 ASA) | |
|---|---|
| clear, sunny | ƒ16 @ 1/125 |
| hazy sun | ƒ11 @ 1/125 |
| bright clouds | ƒ8 @ 1/125 |
| dark overcast | ƒ5.6 @ 1/125 |
