snapsy wrote: randomguy wrote: snapsy wrote: randomguy wrote: snapsy wrote: randomguy wrote: Tony Ross wrote:
Yes, ACR supports lossless compressed RAW-L and lossy compressed RAW from the A9 III (I tested the lossy compressed RAW unintentionally - it's the default RAW format.)
Yes actually note that the buffer capacity is halved with lossless compressed RAW. I guess the firmware compresses the file when it is written to the card and not before buffering it. This is also something they should be able to fix with an update.
Can you explain why you believe the timing of the image compression within the shooting/processing pipeline affects the buffer capacity?
You can obviously fit a larger number of compressed files in a fixed amount of storage, than the larger uncompressed files. The lossless compressed files are not much larger than the lossy compressed files so you would expect a similar number of files in the buffer. But that is not what is happening. So my suspicion is that lossy compressed files are compressed before they are put in buffer while the lossless are not. Perhaps already on the sensor.
For context here are the numbers from the A9 III manual:
Buffer Capacity for continuous shooting:
raw uncompressed: 96 images
raw lossless compressed: 96 images
raw lossy compressed: 192 images
Number of files that fit on a 64GB card:
raw uncompressed: 1100
raw lossless compressed: 1800
raw lossy compressed: 2000
Like previous Sony bodies, the A9 III switches from 14-bit to 12-bit readout when using lossy compression in continuous shooting mode (source). The 12-bit raw frames in memory will take up less space than 14-bit frames even before compression is applied. I'm guessing the buffer capacity relates to that, and perhaps also due to the performance difference of the compression algorithm, and that both lossy and lossless compression are compressed at the same stage in the processing pipeline.
12vs14 does not explain a doubling of the number of files in the buffer. 8bit per pixel as in lossy compressed file vs 16bit (uncompressed) does.
The number of images that fit on a card seem inaccurate to me, a sample ISO 3200 image out of my window just now is 27.3Mb lossy vs 31.9 lossless.
Going by the Nikon Z6's 12 vs 14 bit lossless compression, the 12-bit is 15% smaller. And that's only accounting for the final output. It's unclear if the in-memory arrangement of data would match this.
The capacity will likely vary based on image content and noise. You're seeing a 17% reduction in size vs the 11% implied by Sony's sample table. Doesn't seem that far off to me when also accounting for the potential differences on assumed average scene content.
I am seeing a much bigger reduction of size with lossless compression, a uncompressed raw has exactly 16bit per pixel while the lossy compressed has 8bit. Which should put the uncompressed files at 24Mb larger than lossy compressed or 51.3Mgb vs 31.9 lossless. Which is almost 38%.
Feb 10, 2024 at 10:32 AM
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