dclark Offline Upload & Sell: On
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Three additional bits of information.
1. I forgot to mention that the buffer indicator that can be displayed on the left side of the EVF (Menu: Setup > Display Option > Remain Shoot Display) is not accurate at all. When shooting it shows the buffer is full at 150 frames when it has quite a bit of space left if shooting with a CFE-A. When clearing the buffer, it shows the buffer cleared when there are still 50 frames to go. Its a minor issue, but don't depend on that display for accurate information.
2. These charts and data points depend on file size and frame rate. The average file size for Sony's compressed files is pretty stable but does vary a bit depending in how much compression the embedded JPEG images have. The same should be true for uncompressed. Lossless compressed file size may vary quite a bit. Shooting JPEG or including JPEG files with also add variability in the file size.
3. This data can be scaled for file size and frame rate and should be a pretty good predictor of the results for other file formats. The Buffer Clearing Rate chart should not change, except for the possibility that it will be a little bit faster to write large files than smaller files.
Scaling the first chart is based on computing the rate at which the buffer is filling. The formula is:
BFR = FR*FS - BCR
Where, BFR is Buffer Filling Rate, FR is Frame Rate, FS is File Size, BCR is Buffer Clearing Rate.
In the case presented, FR=30/sec, FS=54MB, BCR = 587 MB/sec for CFE and 246MB/sec for UHS-II.
You also need the size of the Buffer, BS, which is 127*FS = 127*54MB
Time to fill the Buffer = BS / BFR.
Once the buffer is filled, then BFR = 0, so the FR drops to FR = BCR / FS.
Note that the BFR can go to zero or negative in the formula above. That means there is a FR*FS below which the buffer clears as fast as it is being filled and the buffer will never fill. For example, with the CFE-A, Compressed RAW, at 10fps, the buffer never fills. You can shoot continuously until the card fills.
Since the Buffer Size and the Buffer Clearing Rate do not change with File Size or Frame Rate, the time to clear the buffer does not change, it is 11.5 sec or 27 sec regardless of how you managed to fill the buffer.
This gives you what you need to predict the results for different file sizes and frame rates.
Another point of caution is be careful to include the proper number of factors of 1.024 in file sizes and specs. A kB is 1024 bytes. A MB is 1024*1024 bytes. A GB is 1024*1024*1024 bytes. Lots of errors on internet postings can be traced to this error.
Dave
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