Luminance or Illuminance ?

Started Mar 28, 2013 | Discussions thread
Tom Axford Veteran Member • Posts: 3,760
Re: Luminance or Illuminance ?

GeorgianBay1939 wrote:

Swamp Duck wrote:

It has been my thought that Luminance was the light reflected from a given subject, Illuminance was the light on the subject?

Yes, that is what I am concluding also. But, contrary to most photo essays, I see no reason to care about the light on the subject.  I really, really care, though, what my camera's sensor is sensing.

That was a significant reason why I decided on a MFT camera with a live view EVF instead of a DSLR with an OVF a couple of years ago.  Of course there were other reasons, especially the ability to use good small diameter, short lenses.



I think one of the historical reasons for caring about the light on the subject was in a method of metering that was more common in the days of film: that of using an incident light meter (measuring illuminance) instead of using a reflected light meter (measuring luminance). These days, metering is nearly always by the camera which is essentially a reflected light meter.

The advantage of using an incident light meter was that white snow came out white and a black cat came out black, whereas using a reflected light meter both would come out mid-grey (if they more-or-less filled the frame).

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