Matt White wrote:I got this information from my vendor, who said that at this time there is no CFAST card fast enough to record the full capacity of the camera (4.6k RAW 60fps), so the only way to use that setting is with an external recorder. via SDI.
Personally, I have no need for uncompressed raw right now, so I am not concerned.
Matt, true 60 fps uncompressed raw exceeds the recording capability of an existing CFast 2 card in the URSA/Mini. But remember two things:
First, 'uncompressed' is actually lossless compressed raw much like you can zip a data file and then unzip it without any loss of data. That lossless compression fa or varies with your scene but is likely somewhere in the range of 1.2x to 1.5x for video. Generally I assume a factor of 1.3, but to play it safe, let's assume it's 1.25x for our busy video.
Second, for high frame rates, the CinemaDNG raw files are supposed to use the camera's dual record option, so all odd DNG frames are on one card and the even DNG frames on the other card.
You need to use both of those things to allow you to record raw 60 fps open gate on the 4.6K sensor. The camera always records uncompressed raw as lossless compressed raw, but you need to select the dual record option with two cards in the slots.
4608 X 2592 = 11,943,936 photosites/frame
X 12 bit raw = 143,327,232 bits/frame
X 60 fps = 8,599,633,920 bits/second
/ 8 bits per byte = 1,074,954,240 bytes/second
/ 1.25 lossless compression = 859,963,392 bytes/second
/ 2 cards = 429,981,696 bytes/second/card
+ audio 24bit 48KHz 2 channel recorded on each card
(2,304,000 bits or 288,000 bytes per second).
So you need two cards each of which must record with a sustained data rate of 430,269,696 bytes per second. The Lexar 3600x cards are rated at 445 MB/s. So they should work depending upon the amount of lossless compression.
The Transcend 3400x CFX650 cards are rated at 370 MB/s. They should fail except on simpler scenes that permit higher values of lossless compression.
I think the vendors are following the traditional 'computer' definition of a megabyte and kilobyte:
1 MB = 1024 KB and 1 KB = 1024 bytes, therefore
1 MB = 1,048,576 bytes.
If I'm correct in that assumption:
the Transcend's 370 MB/s is actually 387,973,120 bytes per second. Subtracting 288,000 bytes per second for audio, leaves 387,685,120 for video. With a perfectly reasonable lossless compression factor of 1.4x, this can be done. But in a very busy scene the Transcend may have dropped frames.