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Forum: General Photography 01-23-2019, 09:13 AM  
What interval does a light meter read?
Posted By photoptimist
Replies: 10
Views: 604
The "interval" depends on the camera but all modern cameras almost certainly use a variable integration period (what you called the "interval") that depends on the light level. As for RGB, the newer Pentax cameras have a RGB array sensor not unlike a tiny camera so they meter each color channel independently. Older cameras had a simple photodiode which has the default spectral sensitivity of silicon and no ability to distinguish color although they may put a slightly colored filter on the sensor to help match it to the main sensor.

The point is that the exposure meter is essentially a tiny camera with an electronically-controlled shutter speed. The shutter speed the meter uses is almost certainly faster than 1/60 second in very bright conditions and definitely slower than that in very dim conditions. That's the only way the system could get accurate readings over the huge range of EV levels (from -3 to +20 for the K-1).

As for light source flicker, there are many clever tricks for detecting it, filtering or averaging it out, and timing the main exposure to occur in synchrony with the flicker.

P.S. The AF system does the same thing.
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