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> Foot Candle Requirements For Red

>Published : 13th May 2009

Can anyone out there help me figure out what the foot candle requirements are for a Red camera shooting 120 fps with a 1/2000 shutter? My math tells me something like 10,000 foot candles and that seems a little high.


Thanks,


Marty Mullin
DP
www.martymullin.com
Los Angeles
818 712-0272
305 606-1262


Given the rule that 100 ASA at f/2.8 at 24 fps (1/48th shutter) needs 100 fc...
And rating the RED at 320 ASA, then at f/2.8 (1/48th) you'd need 32 fc... but with a 1/2000th shutter (the frame rate matters less than the shutter speed in this case)... my calculation came out to 1,333 fc. Don't know if my math is right though.


David Mullen, ASC
Los Angeles




>>Can anyone out there help me figure out what the foot candle requirements are for a Red camera >>shooting 120 fps with a 1/2000 shutter?


The same as for a RED ONE shooting 24fps at 1/2000 shutter, grin.
I rate R1 at EI320 for most work. My light meters tell me I can shoot at T/2.8, 1/48 sec at about 33 fc, and T/2.8, 1/2000 sec at about 1580 fc. Or, at T/4, 1/2000 sec, figure on 3160 fc.

(The math is: fc @ 1/2000 = fc @ 1/48 * 2000 / 48; the ratio of footcandles is equal to the ratio of exposure times. My lightmeters agree with the math, plus or minus a few footcandles.)


Adam Wilt / filmmaker, Meets The Eye / writer,
provideocoalition.com / Mt View CA USA




> (My lightmeters agree with the math, plus or minus a few footcandles.)


Actually my lightmeters put me more around 1200 fc instead of 1580 for T/2.8 @ 1/2000 sec, EI 320. The 1580 was doing the math based on a quick reading at 1/48 sec.


Adam Wilt / filmmaker, Meets The Eye / writer,
Mt View CA USA




I'm not very good at formulas so I tend to take the long way around...


Figuring from the old rule of 100 ASA / f/2.8 (1/48) = 100 fc, then I get for 320 ASA:


1/48 = 32 fc
1/96 = 64 fc
1/192 = 128 fc
1/384 = 256 fc
1/768 = 512 fc
1/1536 = 1024 fc
1/3072 = 2048 fc


So divide 3072 by 2000 and you get 1.536, so divide 2048 by 1.536 and you get 1333.3333.... hence my figure of 1,333 fc for 1/2000th. But maybe my math logic is faulty...


David Mullen, ASC
Los Angeles




I'd cheat a bit and boost your light levels above what the calculations say you need. I leave the RED set at 320 but light a bit brighter and "expose to the right" to stomp on noise. I set my meter at 160 as a safety and then set exposure based on what I can get away with highlight-wise.
-------------------
Art Adams | dp
san José | ca | usa
www.artadams.net
art.provideocoalition.com
415.760.5167