Metering Techniques

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Metering is a vital part of any photography, whether inside the studio or out on location.

I know that some photographers these days who use digital cameras may feel that they don't need to use a separate flash meter in the studio, but let me tell you, a meter is an invaluable tool. Most studio photographers I know wouldn't be without a flash meter and there is a good range of models available on the market today.

Using a flash meter is easy, they all work in pretty much the same way. Some may have more buttons and read outs, but they all do the same job. Basically by setting the ISO of the film and the shutter sync speed of the camera and the flash meter will tell you what aperture to shoot at.

If you are using film, set the ISO as usual, if you are shooting with a digital camera I would recommend a setting of 200 ISO.

The camera shutter, or sync (short for synchronisation) speed used with flash is important, you can use any speed between a 60 th and a 250 th, but I would recommend 125 th of a second. This speed will give you plenty of latitude and you won't get any 'cut off'. Cut off is caused by using a shutter sync speed that is too fast for the lights that you are using and only half of the shot will be exposed, the other half will be 'cut off' and not exposed because of the speed of the shutter opening and closing too quickly.

I have used Gossen and Sekonic meters and both companies make great products. Most meters these days are digital and have a simple read out and display. To trigger the flash, meters have a coax socket, so that a standard sync lead can be attached from a flash head to the meter. Or if you have an assistant to fire your lights you can use most meters cordless! Measurements are very accurate, usually in tenths of a stop.

So far so good, but how do we actually use the meter?

You can do this in a number ways. By measuring the light that falls on the subject and setting the aperture that the meter gives you. Or by measuring the light on the subject, then reducing or increasing the power of the lights to give you the aperture that you want.

Let me explain, say that you have a simple two light set up for a portrait shot and you want to shoot at between f 8 and f11 to give you good depth of field. By using the meter we can determine the amount of light falling on the subject and by adjusting the power of the lights up or down, we can get the aperture that we need, say f11.

Also by using the meter we can easily set a 'ratio' of say two to one or even three to one. A ratio, meaning that we can set one of lights as a main light and the second light as a fill in. We can do this by using the meter to help us adjust the lights and set them two stops or three stops apart. So our main light will give f11 and our fill in will give us f5.6 / f8.

This ratio will help to build some shadow into the picture which gives the face of the subject shape and form. If we lit the portrait with both lights at equal power, the light will be even, but rather bland, by introducing a ratio we can get more interest in the picture.

Where do we actually point and position the meter?

Common sense is used here, obviously the measurements are taken from the 'highlight' areas. When we shoot people the lightest areas will be on the skin tones and maybe clothing. When we look at a person the forehead, cheeks and noses are the best places to meter as they will reflect the most light. If the subject has white clothes we can also take measurements from these areas. So position the flash meter so that the 'cell' that receives and measures the light is exactly on one of these 'highlights'.

With the meter programmed and the sync lead attached position the meter on a highlight area, take a reading of each light and a further reading pointing the meter direct at the camera. You can then begin as we have already said to adjust the lights up and down in power, either to set a ratio, or to select a preferred aperture. When the lights are fully adjusted and the preferred aperture or ratio is achieved the shot can be taken.

So we can use a flash meter to help us adjust our lights to give us a working aperture, to set a ratio to create subtle shadow areas and save us a great deal of time and money whether shooting on digital or film. For more technical work, such as multiple flashes, a flash meter is invaluable

If you are using studio lighting without a flash meter, but you've thinking about buying one, I would look at meters made by Gossen or Sekonic they are all very well designed and easy to use and from companies that have been making meters for a long time.