maybe we are making progress...
I downloaded that SD card tester, and my San Disk Ultra Plus 80 MB/sec card that has been supposedly tested to write at 34.4 MB/sec in a Canon 6D only writes at 13.8 MB/sec.
The SD tester site says San Disks are notorious for not meeting spec...maybe WalMart is selling Chinese fakes?
I don't know whether it matters what computer it's in, I'm using a Dell Latitude E6330.
BTW, the read speed was 64.7 MB/sec.
(Great app btw, I'll be testing every card I get from now on!)
OK, it looks like maybe this could have been my fault all along. I know at least one of you pointed out that the read speed rating prominently displayed on the card doesn't indicate the write speed, which I understand, but I wrongly assumed that a card with a faster read speed would also have a faster write speed. I am apparently currently using a U1 card, and I didn't realize those are rated so slow on write speed. It might be that all the cards I have always used in this camera are not rated more than U1.
Thanks for all the help. I have a San Disk Extreme Pro 95 MB/s U3 card arriving tomorrow, and will update when I test it. I would not have figured this out on my own. Thanks again.
We don't really know what the Read Speed and Write Speed is of your SD slot in your notebook.
What a coincidence though - Your test does match the ~10 MB/s Write Speed in your Canon 6D.
This was the URL to the best "Write Speed" for Canon 6D ...
And I don't even see a SanDisk Ultra listed!
I recently read that the SanDisk Ultra actually has a very poor Write Speed, even though it has a very fast 80 MB/s Read Speed.
Yes, the fastest "Write Speed" for Canon 6D was ...
SanDisk Extreme Pro 95MB/s 64GB SDXC UHS-I U3 Memory Card
I don't think we can do better than the SanDisk Extreme Pro, since the Canon 6D does not support the newer higher speed V90 or UHS-II technology.
The Read Speed and the Write Speed should be required specifications on every SD label.
Actually, the Write Speed is the more important specification since it is always the slower value, sometimes waaaay slower.
Marketing - arrrg !
Edited by mvas, 18 November 2017 - 02:32 PM.