5.4. How to operate an incident light meter
The first thing you need to do is to set the ISO/ASA of the meter to the film’s speed. Once this is set, you must choose a starting shutter speed. If you have no idea where to start, for outdoor shots set your shutter speed to a number that is close to your ISO/ASA of the film. For example, if you are using an ISO 64 film use the shutter speed of 1/60 second. If you are using ISO 400 film, then use the shutter speed of 1/500 second (since there are no 1/400 sec. on your shutter speed dial). Once you’ve done this, place the meter in the path of light as shown in the diagram, with the white bubble facing the source of light, with its back toward the subject and then press the button.
This type of meter, very much like a spotmeter, works with Exposure Values (EVs) and provides the photographer with a range of equivalent exposures to choose from. For example, for a sunny subject the exposure could be 1/60 @ f-16, 1/125 @ f-11, 1/250 @ f-8, 1/500 @ f-5.6, 1/1000 @ f-4 and so on. As you know, each of these combinations produces the same exposure on the film.
If you wonder which one of these exposures is made for you, the following is a quick review.
The rule is that if your subject is moving fast, or if you are interested in shallow depth-of-field, you use the combinations that use shutter speeds like 1/250, 1/500 or 1/1000 second. If you are interested in maximizing the depth-of-field and you are photographing a subject that does not move, then you need to use the combination that uses the smaller apertures such as f-16 or f-22.
Choosing the right aperture and shutter speed combination is very much like going to a food store and choosing a TV dinner. Assuming that all of them cost the same, you will choose the one that has a combination that you like best.
A special note: The aperture opening (f-stop) reading that is displayed by the incident meter is not always a whole f-number, i.e., f-16, f-11 or f-8 or f-5.6. The decimal point to the right hand side of the f-stop indicates the aperture in 1/10 stop divisions. For example an aperture setting of f-8.5 is 1/2 stop between 8 and 11 and an aperture setting of 5.6.8 is 8/10 (or .8) of a stop smaller than f-5.6 or 2/10 (or .2) of a stop larger than f-8. In this book, to simplify things, we will ignore the decimal point. For practical purposes, to transfer this reading to the lens, the photographer must round it up or down to the nearest 1/2 stop.
For example the aperture setting of f-8.8 can be rounded up to f-11, the aperture setting of f-8.6 can be rounded down to f-8.5 (1/2 click away from f-8) and the aperture setting of f-8.2 can be rounded down to f-8. If you ask why the manufacturer comes up with 1/10 stop divisions when the best you can do is ½ stop adjustments on your camera, you must realize that transferring these settings to the camera is not the only function of this reading. These meters can be used in the darkroom under the enlarger to reproduce an exact density on paper or for comparative analysis. Finally, when copying large art work, you can obtain readings from each corner and the center of the art work to ensure the uniformity of light on the subject.
Copyright 1999, cpgbooks, The confused photographer's guide to photographic exposure and the Simplified Zone System by Bahman Farzad

The confused photographer's guide to photographic exposure and the Simplified Zone System by Bahman Farzad covers the Simplified (5-stop) Zone System, Incident metering, spotmetering (spot metering / Partial Metering), Pentax Spotmeter used as example) Misc. exposure techniques from Sunny-16 to Moony-64.

Copyright 1999, The confused photographer's guide to photographic exposure and the Simplified Zone System by Bahman Farzad