50 to 30 fps calculation

[Christoffer Glans]

We're shooting a spot that has a timebase of 30 fps but we want slomo that works with European lights so we shoot it at 50 fps. Now, the spot is supposed to be 20 sec exactly in one take so I'm trying to calculate the exact shooting time. Is there an app or something that could help with that or someone who does these calculations numerous times help speed this solution up?

Also, why can't we choose 30 fps exactly as our timebase in camera? We only have 29,97, which should work, but I don't get why we can't get 30 flat?

 

[Keith Van Orden]

Unless I'm mistaken, your formula for frame conversion should be Rt(Tfps)=St(Sfps), where Rt is your final Runtime (in seconds), Tfps is your Timebase frames per second, Sfps is your Shoot frames per second, and St is your Shoot Time (in seconds).

So for you, your equation would be 20(30/1)=St(50/1), which simplifies to 600 = St*50 and then finally to 12 = St.

So, if you're shooting at 50 fps and you want 20 seconds at 30fps, your take must be 12 seconds long.

I'm thinking 29.97 should work for you.