Filming for slow motion

[Lee Turner]

Hey everyone,

I really must be thick, i can't work out the best format to film in on my AF to slow down the footage. I use twixtor in AF and with my 7d 60fps 720 setup it works a dream, I thought this new AF you could film the same but in 1080.

I tried 1080 60p and no luck, its really getting to me now. Please help.

[Kevin McRoberts]

To get 1080p60, pick your target sequence frame rate (24 or 30 etc). Select the rear dial function for frame rate and dial in 60. It will automatically confirm to 24 or 30p as slowmo, but MOS.

Always set your shutter speed to 180.0d for best results.

To shoot 60p with sound, shoot in 720p60.

[John Wiley]

Actually Kevin, if you know you're going to be slowing the footage down, it best to ignore the 180 degree rule. Getting the sharpenst image to begin with (ie no motion blur) will allow allow Twixtor to do its thing much better. If Twixtor has a crisp, sharp image it is better able to track pixels and interpolate new frames.

When I shoot surfing at 50p, I never use the 180 degree rule. I shoot anywhere from 1/250 to 1/2000, and even when playing back the footage in real time I find this looks much better than 1/100th, which turns to a blurry mess with so much movement in the frame. Slowed down, the faster shutter speed looks much better, giving sharper images and clean motion rather than a muddy, blurry haze.

[Kevin McRoberts]

I mentioned the 180 rule because...
a) ...I don't use Twixtor;
b) ...In VFR mode, the AF100 will auto-adjust syncro-scan shutter (180d, 90d, etc) to whatever varied framerate you pick... so regardless of shooting 25, 28, 54, or 60 frames per second, the footage will appear to have the blur properties of your syncro scan shutter rate.
If you choose a timed shutter speed (1/48s, 1/125s, etc), it will stay at that shutter speed regardless of framerate. When you then double/triple/quadruple the clip's effective duration via VFR, you proportionally affect the shutter speed... so, in your example, that 1/100 shutter speed now becomes 1/50, 1/33, or 1/25 with, as you note, mushy results.

If Twixtor indeed loves the crispest image possible and you're planning to interpolate frames, then sure, go for the fastest shutter speed possible. If you just want the AF to do the slow-down work, you can just use VFR and a syncro-scan shutter.