Following on from John's comments on incident light metering I thought I would add a comment and explanitory pic or two.
As John describes taking an incident light reading is dead easy. You are measuring the light falling on the subject so the meter needs to be pointed from the subject towards the camera. If you are doing it from the camera position remember that it will only be accurate if the lighting condition is similar as that at the subject position. It would not be accurate if you were in the shade of a tree and the subject in bright light or vice a versa for example. Only a reflected light reading would work here. The incident method of light reading is totally accurate where the light reading is taken from the subject position and the meter pointing towards the camera.
In response to Christine's concerns about using histograms to determine the accuracy of exposure, I will now probably commit heresy now by saying I have NEVER used that method ..... there you go, I've said it.
The light was getting a bit low when I tried the set up from which I made a composite, ( incident reading 1/15 sec @ f5.6 ). I lost the exif info when I rotated the images so unfortunately cannot give that info. The thinking was that it would show in line with Duncans comments in his exposure threads that a light meter will always give a reading to correctly expose to 18% grey. Left to their own devices they will give exposures that will turn a dominant white/light scene to grey and a dominant black/dark scene to grey. ( Under exposure and over exposure ) The images have only been cropped to form a composite and a touch of sharpness added, otherwise they are straight out of the camera.
There are 2 light meter images.
One is to show the diffuser that allows incident light reading. This has to be slid over the meter eye for such a reading. So any meter without that cannot be used to take incident light readings.
The second image shows how easy it is to see the effect of an increase in ISO on shutter speed and aperture. When looking at the meter only bother to look at the ISO setting, time and aperture. This is a pro meter, so is capable of more complex measurements to which the other numbers refer.
Before someone mentions spot metering, I am quite happy to acknowledge that as long as you understand what to meter, that is an excellent method, and is well suited to a wide range of subjects.
Don
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