Calibrating Your Camera's Light Meter

Cameras do not usually come correctly calibrated from the retail store or repair shop. If four cameras are sent off to be cleaned or repaired, all four will more than likely be returned with different meter readings. We can not stress to much the importance of calibrating your camera so that you have a starting point. This calibration procedure should be repeated every 6 to 12 months. 

Take the following photos and select the one that best represents medium tone. To keep track of each of the following settings, we suggest you write each ISO, Shutter Speed and F/Stop combination on an index card and place the card within your picture. (A white index card could suffice for the white subject needed in each picture.)

• Set up your subject in the shade using multi colors to include a solid black and white.

• Put your ISO on the number of your film speed. (For the sake of simplicity we will explain the process using 100 speed film; therefore, put your ISO on 100.)

• Set your F/Stop at F/8.

• Place your gray card beside your subject being sure that both the subject and the gray card are in the same light.

• Now take a meter reading off your gray card and turn your SHUTTER SPEED dial until you have the correct exposure. If not, fine tune with your F/Stop. Take the picture.

• For the next picture move your ISO dial to the next highest number (125) and then move your F/Stop until the camera indicates that you have the correct exposure. Take the picture.

• For the next picture move your ISO dial to the next highest number (160). Then move your F/Stop until the camera indicates that you have the correct exposure. Take the picture.

• Repeat this same procedure in the same direction three (3) more times using the following ISO numbers: (200), (250) and (320).

• Return your ISO dial to where you first started your calibration exercise (100).

• Repeat the above procedure going in the other direction – toward the lower numbers. Use the following ISO numbers: (80), (64), (50), (40) and (32).

• Now go back and select the picture that best represents the subject and, therefore, would best represent medium tone. Pick the ISO number that coincides with that picture and set your ISO dial to that number. This is the ISO number you will use while using 100 speed film.

EXAMPLE: If in the above exercise you chose a picture with an ISO setting of 64, that means you are 2/3 of a stop below your 100 speed film; therefore, when using any film speed other than 100, you will set your ISO dial indicator 2/3 of a stop below that film’s speed.

The above procedure is not as complicated as it sounds. The whole procedure can be done in about 15 minutes. Once this calibration is completed, you will develop a real confidence in your camera's light meter. 

© Bill and Linda Lane, Nature's Image

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