Metering Methods Part 1

Photo by Patrick Hendry on Unsplash

Measuring light isn't always just a case of pointing your light meter at a scene. Depending on the subject, the lighting conditions, and the picture you have in your head of how you want the final image to look, you will need to adapt how you use the meter for each situation.

How do you meter for something illuminated only by candlelight? How about a landscape in the fog? How about capturing a sunset with a silhouette foreground? How do you meter for scenes with lots of shadow as opposed to scenes in bright light? Is metering for colour the same as black and white?





Average Metering
In this approach a mean value is taken of the light and dark parts of the scene. Provided neither is excessive this should give acceptable results. This is where pointing and reading works okay.

Use: When light and dark are reasonably evenly distributed.
Don't use: When something very light or very dark occupies a significant portion of the scene.

The Sky
When the scene contains a lot of bright sky, the average reading risks underexposing the foreground. Tilt the meter downwards to take the reading from the foreground. The risk of underexposure is greater on overcast days when all of the light comes from the sky.

For silhouetted foregrounds, ignore the above and meter for the sky.

Scenes with large highlight areas
The risk here is that the reflected light reading will be too high and the shadows will be underexposed.
Approach 1) Increase the recommended exposure by one stop.
Approach 2) If it is possible to get close to the shadow area so that it fills the meter's view, a reflected light reading may be taken of the shadow to ensure it exposes correctly.
Approach 3) Take an incident light reading. Stand where the subject is. Fit the diffusing screen over the meter cell. Point the meter back towards the camera. This will take a reading of the light falling on the scene and should give an acceptable exposure.

Scenes with large shadow areas
Here we have the opposite risk of overexposing the highlights.
Decrease the recommended exposure by one stop, (two if the shadows are very large).

Low contrast scenes
When the scene contains only mid tones, reduce exposure by one stop. It is possible to increase contrast in development by extending development times, though this is only practical on roll film if every shot is in similar light conditions. 

High contrast scenes
You may have to choose whether the highlights or the shadows are more important. Too little exposure will remove all shadow detail. Too much will blow out the highlights. One approach would be a high-low reading:
Get close to the subject and take a reflected reading from the brightest and then the darkest areas. Adjust the settings until you are mid-way between the two and shoot.

How does this help when shooting a box camera?
Being aware of these different approaches can help you decide whether a subject is suitable for your camera or not. A landscape with an average distribution of light and dark may well come out fine. Dark foreground on an overcast day will probably be underexposed.

If you need to reduce the exposure times, you can use neutral density filters or, in the case of a long exposures lasting seconds, reduce the length by 1-2 stops. If you need to increase the exposure (and the subject is stationary) you can take the shot more than once.

Another important skill is recognising when a subject is beyond the scope of the tools you are working with. Decide what the important parts of the scene are and then decide if the camera can take them successfully. Work with the cameras limitations to avoid disappointment.