How do light meter Apps measure up?

Posted by Nigel Goldsmith on Monday 27 June 2011 at 8:54am
Tags: equipment | hardware | photography |

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The majority of today's cameras have build in light meters which can deliver good results under average conditions, under atypical lighting however the results may not be quite so good. With digital photography the shots can be taken and then reviewed, if necessary adjustments are made to the exposure before a second hopefully more pleasing image is taken. With film the results are not seen until the film is processed which is often too late to make the corrections to exposure. For both media types a hand-held light meter will normally give far more accurate exposure values and if used with care is less likely to be confused by the tricky 'black cat in the coal cellar' shots.

Hand held light meter

Recently a few smart phone software developers have released Apps that use the phone's camera as a reflective light meter. I was reluctant to believe that a small bit of software could compete with a dedicated light meter that is significantly larger than a phone. I set up my Minolta light meter to measure light reflected from the subject to match the method used by the App and the measurements were compared. Most of the readings were exactly the same if used with care, at worst a few measurements were 1/3 of a stop (unit of exposure) out.  This I feel is an acceptable range for an emergency meter if used with negative film or digital cameras. With slide film I would normally shoot a range of slightly different exposures (exposure bracket) based on the meter reading, one of the shots at least should be useable.

Light Meter App for iPhone

Dedicated light meters normally have a diffusing cone which can be positioned over the light sensor to measure the incident light this is the light falling on the subject. This type of reading is preferred by most photographers and cannot be measured using a camera's built in reflective meter.

Reflected light meter such as the App or a camera meter are prone to errors however, if the meter is pointed at a 18% grey card or a similar toned subject (palm of hand, large area of lawn etc) that is illuminated by the main light source then it should be almost as accurate as an incident meter.

The only other shortcoming of these Apps is their inability to measure flash light but this failing is also shared by most built in camera meters.

While I will still carry my ancient Minolta meter for serious jobs I would quite happily trust this type of App as a backup.

The App used for this test was Pocket Light Meter, the light meter was a Minolta Autometer IV-F

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