What 250 in (250 / ISO) stands for?

jocelyngirard / erixposure-arduino

An Arduino light-meter for photographers

GNU General Public License v2.0

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What 250 in (250 / ISO) stands for? #1

Open vegetableswim opened 5 years ago

vegetableswim commented 5 years ago

I'm trying to make a reflected lightmeter these days, and seeking for the algorithm. I don't understand the (250 / ISO) part in your code? Could you give a clue, plz?

jocelyngirard commented 2 years ago

Hi @vegetableswim,

Sorry for the long delay before replying you !

The 250 is the Sekonic's constant value for incident light metering. Need to be adjusted if the enclosure or metering components differs.

More info for light meter equations and calibration values : http://www.yedlin.net/NerdyFilmTechStuff/ExposureEquationsAndMeterCalibration.html

vegetableswim commented 2 years ago

Still thank you very much because your code encouraged me to seek the formula of EV and Lux ,during these years I made my own DIY light meters and they work well :D