Using light meters

Lawrence

Senior Member
A quick question.

The other night I was the "assist" shoot at a children's variety show and the main shooter, a professional wedding photographer, was using a hand held light meter.
What the hell was she measuring?
I found I was quite fine with my much lower-end gear while she had much more expensive (insert C word here) gear and fancy flashes.

Seriously where/when would one use a light meter?

I can only think it was to set her flash and that is an absolute stab in the dark.
 

WayneF

Senior Member
Seriously where/when would one use a light meter?

I can only think it was to set her flash and that is an absolute stab in the dark.


There are necessary background details needed for understanding, but the easy answer seems this:

1. Camera meters are reflected meters.
2. Camera meters don't measure flash (except TTL flash).

That says it all, but here's more detail.

Reflected meters (camera meters) read the light reflected from the subject. In the same light, the light reflected from a white wedding dress is much brighter than the light reflected from a black tuxedo. The reflected meter sees this, and will read them quite differently (when in fact, neither is correct). That is how camera meters work.

Incident meters (most hand held held meters) can read reflected, but mostly they are used as incident metering mode. These turn our back on the subject, and we read the light source directly, how bright it is, and then the white comes out white and the black comes out black.

Plus, to read the manual mode flash, the camera meter cannot do it, but the incident meter can.

Incident meters are more awkward to use, like for flash, because they have to meter the indent light on the subject. That means we stand at the subject, and aim the meter at the camera, and meter the light directly. The subject (and their reflectivity) is not involved in the metering, but the light actually on them is all important (flash falls off fast with distance, so we have to meter exactly where the subject is).

If in a studio situation, using several lights, the meter is all important. It is the way we set each light to the power level we want it to deliver. We meter and set the lighting ratio of each of the multiple lights. Tedious perhaps, but extremely controlled and accurate. We can get exactly what we want from each light. When using one manual hotshoe flash, we can easily tweak it in by trial and error results, but multiple lights are a whole new ball game.

One strong plus, after we do get our setup worked out, we can easily duplicate same situation next time, by just metering the lights the same way. It is really about exactly knowing what the lights are really doing. :)

If out shooting landscapes, or such, these scenes often average out as a proper mix of dark and light colored areas, and the camera meter is often not so bad. We learn how to get by (compensation).

But see How Camera Light Meters Work for what is wrong with camera reflected meters.
 
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