Jesse Evans
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 p.3 #4 · EOS-R5....will it live up to the hype? | |
So, first, let's just start with stating the obvious, I am purely speculating.
Regarding dynamic range, I said the dynamic range would be 0.5 stops worse at full resolution, which means I'm assuming Canon is not getting better per pixel dynamic range while making the photosite smaller.
I didn't say C-RAW, I said RAW. And just so we are starting off on the correct foot, the buffer capacity is dependent on the selected shooting speed.
At the EOS R's maximum shooting rate of 8fps, the buffer capacity is stated as 78 shots. For RAW files, the buffer depth is 47.
78 shots will take 9.75 seconds to capture.
A C-RAW file in the EOS R is 17.3MB. 78 shots means that before hitting buffer limits the camera should be capable of generating 78*17.3MB = 1349.4MB of C-RAW data.
47 shots will take 5.875 seconds to capture, and will generate 47*31.3MB=1,471MB of RAW data before slowing down.
So, what does that tell us about RAW and C-RAW with regard to buffer? Well, we can't know the exact story, but the main takeaway is that C-RAW's buffer is limited by the processors ability to turn raw files in to c-raw compressed files, and the RAW buffer is limited by the ability to take RAW data and write it to disk.
Assuming no other losses in the system, over the course of the 5.875 seconds to fill the RAW buffer, a 200MB/s write speed UHS-II card should be able to write 1,175MB/s. Meaning that were the camera capable of writing to the UHS-II card at its full potential during capture, the actual buffered amount of data at the end of the burst is only 296MB.
For the C-RAW case we have a full 9.75 seconds, which if the camera were capable of writing at full speed during capture would mean we were writing 1,950MB. This would mean that the camera could have an unlimited buffer when shooting C-RAW.
So, what we can relatively safely assume is that the camera has some amount of RAM that is capable of holding RAW data, that is either written to disk, or turned in to C-RAW in memory before being written to disk.
I'm guessing based on these numbers that the amount of buffer RAM is around 1GB, since presumably SOME images are written fully to disk throughout the course of the buffer run before we have to slow down shooting.
With 1GB of buffer, and assuming the EOS R5 generates 45MB RAW files, the RAW buffer capacity for files would be about 23 files. Assuming that 20fps is saturating the bandwidth of the system, there wouldn't be any way to write any meaningful number of files to disk, and so the buffer would be purely limited by RAM.
So, after writing all of that down, I'm going to revise my speculation. The EOS R5 will probably have at least 2GB of dedicated buffering RAM, probably making it possible to capture around 40 raw files in silent shooting at 20fps.
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). The 1DXII already had decent low ISO DR. This number for the 1DXIII puts it near the very best, equaling the D850 (except for its 80 and 64 settings) and getting close to the A7RIII/IV. Not bad Canon, not bad.