Practical calculations with LED lux rating

[Philip Ulanowsky]

I just watched Oren's review from some time ago of the Illumi-max 300, which he indicates puts out 36,000 lux at a meter (Adorma site has it at 132K lux at 0.5 m). I've been keeping a lazy eye on LED developments in the lower-budget range and would like to check my math.

My aging HD camcorder has a practical native exposure index/ISO of about 100; not a low-light camera. For single-person interviews, I use a couple of Lowel's (500 Omni, 750 Tota), which usually have enough power to bounce or pass through a some ripstop, depending on location and needs; or, in tight quarters I can also just barely get away with a pair of daylight 80W CFLs in China balls.

(I am also a still, film ("analogue") portrait photographer with various formats needing more power for adequate DOF/shutter speed.)

As found on one technical site: "The original exposure for 1000 lux (100 fc) is still f/2.8 at 1/50 ISO 100." If my math is right (which might be a miracle), 36,000 lux at those settings would then be sufficient for f/16+ at that distance, or f/8-11 at about 6 feet. Bouncing/diffusion would knock it down to f/4-5.6 or lower.

Am I in target range math-wise? Thanks.