There's Something Wrong Here
Having only just bought two Lexar 64GB 1066x cards, I haven't used them heavily yet. My prior cards were Lexar 64GB 800x, which worked flawlessly with a Canon EOS 5Ds. For this review I decided to do a speed comparison, which turned out to be surprising.
To compare them, I filled the camera's buffer with images, then timed how long it took to flush the buffer to the card. I was shooting RAW + JPEG at maximum capture rate to generate lots of data. I repeated this test a few times, newly formatting the card each go. This wasn't a high-precision test, but was adequate to compare.
One might expect the 1066x card with a movie rating of 65 to be faster than the 800x card with a 20 rating, right? Wrong! Cutting to the chase, the 1066x card cleared the buffer in 33 seconds, whilst the 800x card cleared it in a mere 15. So this new card is over two times slower, when it should be 33% faster! There's something wrong here.
I repeated this test with different 1066x and 800x cards. This gave consistent results, the 1066x card still being over two times slower.
I repeated this test with a Canon EOS 5D Mark II. The 1066x cleared the buffer in about 7 seconds, whilst the 800x cleared it in 5. This difference wasn't so pronounced, but the 1066x card was still slower (the EOS 5Ds has a much larger buffer than the 5D Mark II, so needs a high-performance card).
Whilst formatting the cards in the 5D Mark II, the 1066x card was noticeably sluggish, so again the speed difference was apparent here. I didn't notice this on the 5Ds.
So what's going on here? Let's take a closer look at these cards.
All cards are Lexar branded, copyright Micron Consumer Products Group Inc. (Micron being the manufacturer).
One of the 800x cards is made in Vietnam, model number 508-66179 Rev A; the other is made in China, model number 508-62914 Rev B.
The two 1066x cards are made in China, model number 508-65025 Rev A.
Why would a newer card with a higher speed rating be much slower in the real world than older cards with a slower rating? The 800x cards have "UDMA 7" on them, whilst the 1066x cards don't. Could it be these 1066x cards are not actually Lexar (Micron) originals, but Chinese copies? I don't know. If you search ebay for "lexar 64gb 1066x compactflash", that will return different product images. Some cards have a curvy, gold design, as found on my speedy 800x cards, whilst others have a simpler, non-curvy design. Could these be knock-offs? I don't know.
The 800x cards fit nicely in the card slots of both cameras, whilst the 1066x cards are noticeably stiff to insert and remove. I don't mind them being slightly stiff, but these are just a little too stiff for comfort.
Given the problems this review highlights, I don't think I can recommend these memory cards. If you are a sports photographer, where speed matters, be careful what you buy. I'm not, so this huge speed difference doesn't really affect me. This test does raise questions in my mind though as to whether they are genuine. They seem to work OK in both cameras, so I'll probably stick with them, but be more careful next time. I doubt these are genuine.
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