Quote Originally Posted by Richard Donham View Post
Colin--it has always seemed counter-intuitive, but I have known that you need to increase exposure of a white subject to get it white and decrease exposure of a dark subject to get it more accurately black. The meter will be one more piece of reinforcement so that it becomes more natural, I hope--interested in comparing the reading on the hand meter with the camera's in those situations.
Hi Richard,

The "problem" for any reflective meter is that it can only measure light -- it has no way of knowing if that amount of light is a black dog in full sun, or a white dress inside - so the best it can do is assume that everything is middle gray and let the photographer take it from there. Incident light measurement takes away the guess work though, because for a given amount of incident light, a white object will naturally reflect more than a black object.

Folks need to realise that an accurate incident light reading doesn't guarantee a perfect exposure though, because there are still a few other things going on ...

1. The actual light that hits the sensor is typically about 1/3 of a stop lower (do a "Google" on T-Stops if you're a glutton for punishment)

2. An incident light reading doesn't take back lighting into account (although you can spot-meter it and apply an adjustment) (common for sunrise / sunset photography)

3. All an incident light meter will do is put a middle gray into the middle of the histogram - but - when dealing with reflected light, white is 2 stops more and black is 2 stops less than middle gray - but the middle of the camera histogram may well be 3 or more stops down from the maximum that the sensor can record - so a white dress will still typically be 1 stop "under-exposed" (but if you increase the exposure 1 stop at the time of capture then you end up with whites looking white, but blacks looking gray because they are now 1 stop higher than they need to be) (so in reality it's something that usually gets sorted out in post processing).