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Forum: General Photography 01-23-2019, 12:06 AM  
What interval does a light meter read?
Posted By Alex645
Replies: 10
Views: 603
Can you clarify your question? The title of your post, "What interval does a light meter read?" would imply you're asking whole EV, 1/2 or 1/3, with some incident and handheld meters at tenths of an EV.

But if you're asking because of non-continuous light sources such as the flicker from fluorescent, neon, sodium vapor, LED, etc, I would say it is rather slow and is just averaging the light intensity over a fairly 'long' period of time....such as 1/4 second. From an engineering perspective, I'm sure someone at Sekonic or Gossen or even Spectra Cine could answer this technical query.

In cinematography and video, whenever shooting with non-continuous light sources, to avoid flicker due to the shutter being out of sync with the light source, we had to use high frequency ballasts that pulse at extremely high rates.

Are you wondering this just from a purely theoretical curiosity or is there an exposure concern?

---------- Post added 01-23-19 at 01:20 AM ----------

From a very simplified analysis, at 50Hz, the light is on 50x/second and off 50x/second. There are different ballasts that may increase this, but regardless, of the Hz, it's on half the time and off half the time. So although it may be on more frequently, it's also off more frequently and the amount of lumens or foot candles is going to be the same....unless you're shooting at an extremely high shutter speed with the possibility of missing a burst, at which point, the light meter is not going to adjust to the darkness.

Practical answer: Avoid high shutter speeds (or bracket) when shooting with predominantly non-continuous light sources.

If you want a specific number, you'll need to find an electrical engineer familiar with this particular technology, and even then, I'm sure this is not a constant value on all light meters.
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