- Posts: 344
- Joined: Mon Apr 24, 2023 9:06 am
- Location: Spain
- Real Name: Omar Mohammad
Hey Omar. This is not news, and I always like John's intellectual POV and he's right about 24fps. But good to know that you found a resource on YT that was helpful for you.
IME, there are two equations that I hang on to give me rough calculations of how much light I need. Your decision and choice will be based on what your final intentions are and depending on what creative thing you're doing. But generally, ...
Equation 1:
Like if the higher frame rate selection was to be able to slo-mo, then you'll need to compensate with the light to get equivalent exposure as if you shot it in a slower frame rate. The equation is rather simple: Let X = the frame rate you want to shoot at. Let Y = the natural frame rate usually used, for example 24fps. What I would do is divide X by Y to give me Z, Z being the multiple of light I need to add. For example, if I want to shoot at 400fps (all other cam params stays unchanged), then 400/24 = 16.66 or round it to 17. In this case, I will need 17 times the amount of light I currently have. Using a light meter and checking the amount of light, let's say it's currently at 100 lums to shoot it at 24fps. So, I will need 1700 lums of light to shoot at 400fps.
Equation 2:
Every time you double the frame rate you have to go up one stop. So 24fps to 48fps equals 1 f/stop. 48 to 96 is 2 f/stops, 96 to 192 is 3 f/stops, and so on. So going from 24 to 400, you'll need roughly about ~4.2 f/stops. So with the same lighting (no change in lighting setup) and you're at 24fps 8.0 f/stop, to shoot at 400fps, you'll have to set your aperture to be around f/1.8 - f/2.0.
That's how we (people who I work with) do it. BTW, it's not the only way.