Originally Posted by
rekmeyata
Hmm, ok, maybe I don't understand what you're saying. I have two light meters, one built into and SLR and a really old handheld GE light meter, all they do is give you recommended F stop and shutter speed, or you change one or the other and it recommends the missing factor. All they do is check exposure in an attempt to make a perfect balanced picture. The only light meters that are used in photography are Cine light meters which are not in cameras that I know of and are separate units, and these will measure lux and foot candles. I would assume that IF there is a camera on the market with a Cine light meter it would be very very expensive and for strictly professional users.
Yeah, it's a work around using the camera's suggest shutter speed. Way it works is this: assume you have a trusted calibration light that is 125 lumens. You shine the 125 lumens into a DIY lightbox, with the SLR point into it as a meter, and you vary the ISO and aperture settings until the camera meter suggests 1/125th sutter speed for that calibration light's output, then you lock those ISO and aperture settings, and the camera meter has been "calibrated."
Then, if you shine another light that is twice as bright (250 lms) into the light box, the camera will suggest a new shutter speed of half the time exposure to yield a proper exposure, or 1/250th of a second. If you try a 30 lumen light (~1/4th the output) the camera will suggest 4x the 1/125th time exposure, or 1/30th of a second.
So once the camera meter is properly calibrated, the reciprocal of the suggested shutter speed is your lumen estimate for whatever light or mode you are testing and it even works at sub-lumen ("moonlight") levels - fractions of a lumen are seconds on the camera (eg. 1/10 of lumen is a 10 sec shutter speed).