I'm close to picking up a C70 and am studying up on both the Angelbird and Prograde brand of cards (both V90).
For Angelbird, I'm specifically looking at their AVP256SDMK2V90 parts (the Mark II version of their cards). Quite a bit more cost than Prograde, but I'm seeing some folks finding write faults (or delays due to buffers) for Prograde V90 cards.
What cards have you found to be the most reliable?
Sadly, a V60 should have been enough since that would be sustained writes of 480 Mbps (higher than the 410 Mbps higest bitrate option). But, in a video I found, Canon staff recommends V90. Perhaps to give one some breathing room or perhaps deal with card fragmentation? I don't know if the Video Class guarantees that sustained write speed for say freshly formatted cards (which I always plan to do before a shoot). Or, if that speed is also guaranteed when the card is fragmented.
I'm using ProGrade 128GB V90's in my C70 right now, and after a lot of small tests I've found them to be reliable. I haven't really done any long-form recording yet.
As for speed, camera record speeds can be variable, and flash memory is way more complex than many people realise. So some headroom is a good idea. Theoretically, V90 should be 480 Mb/s under all circumstances, but a bit of margin for error never hurts.
However, the highest specified data rate of the C70 is actually 543 Mb/s, recording in slow and fast for 25FPS, shooting at 120. The camera says 113 Mb/s, but that's the playback bit rate; multiply by the slow-down factor to get the record bitrate, which is what the card has to handle. But again there's some variability. The fastest rate I actually measured was 545 Mb/s, recording for 23.98 but shooting 120.
And the rated speeds are certainly for freshly formatted cards. Fragmented cards will run slower. That's stated on the SDA's site:
I seem to remember you helping me out back in the day with the PXW-X70. Good to "see" you again.
Thank you much for these details. I hadn't thought about the recording bitrate vs playback bitrate. Makes perfect sense. Too bad the manual doesn't call that out.
Wow, really??? That must have been a while ago. Great that we seem to be following the same camera paths!
Re bitrate, yes, slow&fast bitrate doesn't seem to be discussed anywhere, like in the specs, reviews, etc. So I was interested in that, and I decided to measure it for myself.
Forgot to add to this thread. I ended up going with Angelbird. Mark II version of their V90 cards. But so as to save a bit of cash, I got two 256 GB cards and then two 128 GB cards.
I record in DCI-4K 10-bit 4:2:2. So in slot A I'll use a 256 GB card and record in the 410 Mbps codec and then in slot B I'll use a 128 GB card and record in the 160 Mbps codec. So I can have nice backups, though at a lower bitrate. Really liking the flexibility in recording two totally different codecs at the same time.
Total record time is 2 hours 36 mins with this setup which is ample for now.