Key light to t-stop chart?"

David G. Smith

David G. Smith

Steak Knife Member
I have been looking for a chart that shows key light levels, in footcandles, to their corresponding needed T-stop (F-stop) settings for "Normal" exposure at various ISO (ASA) settings. I used to have an American Cinematographer Manual that had one in it. Having shoot video for so long, I forgot about using it. Now, shooting with a large sensor digital cinema camera, I would love to have it again (But am putting off buying another AC Manual...I know, I know....).

Having that chart and the photometric data for the lamps I'm using (Which I have) would make lighting set up design much easier, for me at least.



Does anyone have a link to a downloadable version or have one available they can share?
 
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Almost 100% sure it's 100 foot candles at 100asa to light to a 2.8. You can just go from there, halving and doubling to your hearts content.
 
David G. Smith said:
You know, I can work with that actually. Thanks.
Click to expand...

100 fc @ 24 fps @ f/2.8 @ ISO 100 is the 'magic number' I've seen a number of places. I had to work this through coming from the still photography side and quite use to the spot meter just reading off the 'correct' exposure... like f/2.8 @ 1/8 sec... right...

I broke down and bought the Sekonic 308dc, and then at NAB measured various 'lights' that were on display on the floor to get a better 'feel' for continuous lights... not absolutely accurate because of the amount of ambient light... but at least gives me an idea...

Maybe I'll develop a 24 fps strobe, sync'd up to the camera... that can dump a couple KW-S on to the scene... in a nice convenient package... people probably would go blind... but heck it would be more portable...

But with that magic number you could easily with Excel make a table of various ISO values/F-stops and shutter speeds, and get the required FC values...
 
j1clark@ucsd.edu said:
100 fc @ 24 fps @ f/2.8 @ ISO 100 is the 'magic number' I've seen a number of places. I had to work this through coming from the still photography side and quite use to the spot meter just reading off the 'correct' exposure... like f/2.8 @ 1/8 sec... right...

I broke down and bought the Sekonic 308dc, and then at NAB measured various 'lights' that were on display on the floor to get a better 'feel' for continuous lights... not absolutely accurate because of the amount of ambient light... but at least gives me an idea...

Maybe I'll develop a 24 fps strobe, sync'd up to the camera... that can dump a couple KW-S on to the scene... in a nice convenient package... people probably would go blind... but heck it would be more portable...

But with that magic number you could easily with Excel make a table of various ISO values/F-stops and shutter speeds, and get the required FC values...
Click to expand...

That is the point. I just completed a systematic photometric measurement of all of the lights in my light kit, which includes many "Unconventional" lights, and I want to be able to save a bit of time in lighting set up design with this info, and the key light to F-stop calculation.

Now, is there a magic number for calculating in exposure time or shuttle angle?
 
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