60 Foot Candles

[Charles_Boileau]

Hi,

I'm shooting an event at the end on Jan and the producer told me the course was about 60 FC the whole way.

I'm not super familiar with the intensity I'll get from 60 FC.

Will it be enough to shoot slo mos at 800iso 120 fps with the red?

I understand that this might be very subjective, but any info is welcomed.

Thanks!

 

[Tico Llaurador]

60 FC is very dark as it is. Hi-speed makes it worse. Don't bank just on a 800 ISO setting to save your day. You'll probably be disappointed.

Test. Test. Test.

 

[donatello b]

ISO 320 ... 24fps .. 60fc = F4
48fps = F2.8
96fps = F2 (+1/10)
120fps = f 1.4 (+7/10ths, or F1.8)
above #'s from Spectra IVa (calibrated 10/08)

 

[David Rasberry]

According to my trusty Sekonic Studio deluxe, for 800 ISO you would be shooting around F/T 2.4 aperture at 120fps and 60fc based on a 180 degree shutter or 1/240sec exposure.

 

[Mitch Gross]

ISO 320 ... 24fps .. 60fc = F4
48fps = F2.8
96fps = F2 (+1/10)
120fps = f 1.4 (+7/10ths, or F1.8)
above #'s from Spectra IVa (calibrated 10/08)

Your math is a bit off there. It is a straightforward geometric scale, where halving exposure time eats one stop of light.

The simple rule to keep in your head is 100 ISO + 100fc = T2.8. That's based on 24fps & 180 degree shutter, aka a 1/48th exposure time. From there it is pretty simple math. In my head I would switch the 60fc to 50fc since we're only talking a 1/5th of a stop here and you can always stop down a touch if you like. Here's how I calculate it in my head (It takes far longer to type).

100ISO+100fc=T2.8
200ISO+100fc=T4
400ISO+100fc=T5.6
800ISO+100fc=T8
800ISO+50fc=T5.6
800ISO+50fc+48fps=T4
800ISO+50fc+96fps=T2.8
800ISO+50fc+120fps= T2 2/3rds

Note that there's only a 1/3rd of a stop difference between 96fps & 120fps.

But more importantly, you're really fooling yourself by "rating" the camera at 800ISO. Despite what others may tell you, it is a 320 (or so) sensitivity and all you are doing is digging into the underexposure range of the sesitivity curve. You are sure to bring up a lot of noise, especially if the light is more tungsten-balanced than daylight-balanced. That plus shooting in the 2K window and then resizing this will be sure to show a considerable and perhaps objectional and unacceptable (to you or your client) level of noise.

I would suggest setting your camera to 800ISO, the lens at a T2 2/3 and the sensor to 2K window, 120fps and shoot something that appears correct at that exposure inside your home under tungsten light. Shouldn't be too tough to get in the neighborhood of 60fc near a household lamp. Then run that material through to a complete post (whatever your finished output is to be) and decide with your client if this is acceptable.

And this might be a good time to try a SuperSpeed lens, which can open up to a T1.3 and perhaps really save the day for you. Instead of 800 ISO--T2 2/3 you could be looking at 320 ISO--T1.3 2/3, or even 200 ISO--T1.3, which is definitely better for the 2K windowed sensor.

 

[Charles_Boileau]

Thanks for all the info.

Unfortunetaly i'm shooting sports. So I have to use a zoom. I'll be using a Canon KLL lens which can stop down to 2.1.

The good news is that they are using the footage for HD. So that might help me out a bit.

I'll test it for sure.

Thanks!