Ted, I have a feeling these Komputerbay cards may not be Lexar QA/QC failed cards but acutally Chinese knockoffs of Lexar cards. This is my guess because Lexar doesn't even make a 1200x card that one can purchase on the market - nor does anyone.
Could you please do a benchmark write test on your 1200x using a USB3 card reader and a software program and compare the results of that to a 1000x card in the same test so we can really understand if the camera is a limiting factor here?
Steve, they are really not Lexars that did not pass QC, I am not privy to know their exact sources but the way I was made to understand it is this:
There are only VERY FEW memory chip manufacturers in the world, and they almost all get from the same factory sources. Weather its Lexar, KB, Transcend,Hoodman, Sandisk etc.
They differ in their assembly and use of other components, like firmware, chip controller, etc. But what really drives the price up is Brand marketing and packaging and how low you are in the supply food chain.
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I have a USB 3 reader, however, it is not the one compatible with the 256gig, when I did my camera tests with the 5dmkIII, the camera owner had a transcend reader which was compatible, thats why we were able to test and reformat the card to capacity of 256.
I can only do my test with the card in 128 gig state.