In a prior post I measured the frame rate vs time for CFE-a memory cards in the A1. This post will provide some comparison data for the A1II at 30fps. I have not made the measurements for other frame rates and for uncompressed data. The only situation where most people care about the speed of the camera writing data to the memory card is at the highest frame rate.
The data presented for the A1II is taken with Lexar Gold 160GB ver 2 cards and a Lexar Gold 640GB ver 4 card. You may notice that there is only one curve visible. This is because the data for the cards is so similar that the curves lie on top of each other and any difference is not visible. This is what was observed in the A1 and the A9III for multiple cards with a variety of read and write specs. The performance is determined by the camera electronics, not the memory card, regardless of contrary claims you may find on multiple web sites. In this case the write specs on the ver 2 card and ver 4 are far apart but the camera does not take advantage of the second data lane and the in-camera performance is identical.
The most noticeable difference between the A1 and A1II at 30fps is that the A1II does not have a second break where the frame rate drops to 9.8fps. At least no second break was seen for a burst of 30 sec duration, which is far beyond what anyone (even me) would want to capture. That could be due to a larger second buffer and/or a faster write rate to the memory card.
The buffer clearing is quite quick. The data in the box is for a 30 second burst that captured ~580 files. At the end of the burst there were ~110 files in the buffer. It took 7.3 sec to clear the buffer, which means it was writing to the memory card at a rate of ~760 MB/sec. That is a considerable increase over the 617 MB/sec seen in the A1. That is at least part of the reason the buffer has not filled. If shorter bursts are captured the number of files in the buffer is less and the clearing is faster. E.g. a ~5 sec burst has ~75 files in the buffer and it clears in ~5sec.
The second chart shows the distribution of the intervals between the frames. As seen before, they frames are not uniformly spaced. The average 30 fps and 16.5 fps but the time interval between frames is varies a lot, especially for the slower 16.5 fps.
Dec 27, 2024 at 12:03 AM
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