Slow Motion on Canon Mark 3 Raw

[SwaggyP]

Hi guys, I'm having trouble with shooting 60p with my 64GB Lexar 1000x card. Is it normal to shoot only 5 seconds most before it cuts out using 1920x508? I'm shooting with the 2:35 aspect ratio.

Would you guys have any other suggestions for slow motion using magic lantern raw? I need it for shooting music videos and always slow down the B-roll. If anyone has suggestions, please feel free to give me some advice, thanks!

[Midphase]

What does ML say your required mb/sec write speed is with those settings?

That will tell you whether it's normal or not, for instance if you're asking the card to write 150mb/sec, that won't last much more than whatever can be saved in the buffers.

[NedB]

1920x508? I'm shooting with the 2:35 aspect ratio.

I don't quite get this. 1920x508 is a ratio of 3.77, not 2.35. Can you check your post and correct or explain this? Is "1920x508" a typo or is the typo "2.35"? I started to answer your post with some calculations, but this jumped out at me and needs a response before I continue. Cheers!

[SwaggyP]

@Midphase- Hey, where do I find the settings for mb/sec? and What should they be at to get continuous recording @60p 1920x508? Thanks

@NedB- I select camera Raw option on, Then Q to change resolution settings to 1920. Since the aspect ratio settings is at 2:35, ML automatically puts it in 1920x508, then I stretch it to 1920x818 in post.

[JLRoyal42]

What process do you use to stretch it in post?

[SwaggyP]

@JLROYAL42- I just stretch the clip how you would normally in FCPX, just click and drag. But only stretch vertically.

[jose_ugs]

@SwaggyP... what's more important is, what cam r u on, what's your global draw, last but not least: what's your card benchmark like?
@JLRoyal42: u stretch it in post using your NLE (AEF, Resolve, etc...)
@NedB: 2.35 is 1920x818 (which you get stretched 1920x508 in post)

[NedB]

Arggghh, sorry guys. Forgot about the 1.6x factor in 720p (i.e. 60p) mode. Be that as it may, (1920x508x14bits/pixel)/8 bits/byte means 102,412,800 B/s, or 97.66MB/s. This is probably right around the limit for your card. Because the card isn't quite fast enough to keep up with the data rate (or not even really close, I don't know what your benchmark is), the buffer fills up very quickly and you start dropping frames after only 5 seconds. If you have it set to stop on dropped frames, then that's what happens: it stops.

To test, drop down to a lower total resolution (start much lower) and see if that works, then work your way back up. Where you have a problem, that's probably the limit of your card. But even if you can't shoot 1920x508, a 5dMkIII with practically no aliasing should allow you to shoot at 1728x456 or whatever the next lower resolution at 2.35 (in 60p) is. If you blow it up now to 1920, it should still look pretty damned good. Although there is apparently MORE aliasing (because of the additional 1.6 stretch) when shooting 60p. You're probably going to have to do some thorough testing.

Cheers!

[Danne]

I think I would go for 50fps. Here,s a comparison and a workflow I recently made

[spnsir]

I have a Canon 5DMk3 and shoot on two 64GB Komputerbay 1000x cards. I shoot everything so it stretches to 1920x804 in post. I usually get 10 seconds of record time shooting at 60p, sometimes it randomly stops at 8 seconds, sometimes it will go up to 12 seconds. I have global draw on while recording as well.

[moswanted]

you can't "translate" pure card write speed to actual real world write speed while recording.

my cards benchmark at about 115 MB/s but with increasing frame size and fps whte actual continous recording write speed falls off quickly.

examples:
at 1920x1080 30fps i can write ~90mb/s continously
at 1600x500 50fps i can write ~70mb/s continously

so, the higher the fps, the harder a time the camera has to dump the frames without "choking".

only thing you can do, is actually test out, what resolutions/frame rates your cards can do without dropping frames.