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Response to Calculating GN with 2 heads

from Marcus J. Wilson (marc53@doubled.com)
Good thought. It might work. But experience says that one light will always be just outside the one stop range. Therefore the "Dominant Light" rule applies. This rule works almost everytime and goes like this. 1, meter the subject with both lights but with one light off, then do it again with the opposite light on and the other off. Do not change the location of the meter. If you get two different meter readings, the one that gives you the most light is the dominant light. You can use either light as the base and adjust accordingly. If you have two 150 watt lights, one (the main) directly in front of the subject and one at a 45 degree angle (the fill) and both are the same "distance" from the subject, the GN for the exposure will be the same. If you move one light (the fill for instance) closer to the subject the GN for the fill only will change (It will now be the dominant light). The areas lit by the fill will have brighter highlights than those lit by the main. While not hard, this stuff is literally Physics. I suggest you experiment with some film and keep good notes.

Tow quick tips on meters. Spend the bucks and get a good one. When you doubt your meter, use polaroids.

Marcus J.

(posted 8809 days ago)

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