SD Card Comparison

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The above sells SD Cards which have a much lower writing speed to what it says on the lable.


SanDisk SD Card ULTRA says 30MB/s on the lable and the actual writing speed is 10MB/s which is not fast enough for a quality video recording camera like the Canon 5D mk iii, they need at least 18MB/s.

The camera will record but only for a short time. Only 10 seconds before it automatically stops. Which is clearly not good enough to use with any confidence. The comparison on the right is between a known good card and an identical card with identical lable but the back is plain without the embossed SanDisk.

To find the software used above, search for DOWNLOAD  DISK BENCHMARK.

SanDisk SD Card

Lable Says:

Actual Reading


Ultra - From ebay seller




Ultra - From reputable source





I have made a little video shot and edited on my iPhone and put it on youtube...

How to spot a genuine 16GB 30MB/s SD Card for Canon 5D mk iii camera

Well after spending £27.87 for three cards that don't work, I could have bought two good ones that did work properly for a few pounds more!

The cards were SanDisk 16GB Ultra UHS-I SD 30MB/s Full HD Video 16G SDHC, but clearly not up to the job as described because non of them will record for any length with any reliability in my Canon 5D mk iii camera.

I have discovered several ways to spot the good card if you can get them out of the packet before purchasing them. I even put them under UltraViolet light and you can see the genuine card glows on the back behind the contacts! If you get them through eBay then you have no chance of having a look first.

So my suggestion is don't buy the cheap ones online go to a reliable photographic / computer shop and spend a bit more, at least you can take it back if it doesn't work properly.



Well the plot thickens...
I decided to forget buying cheap on the internet and went direct to the SanDisk website
to find an affiliated SanDisk supplier in my nearest city, Sheffield. They only had one recommended retailer Harrison Cameras on London Road. So I bought two identical cards to the recently purchased cards from ebay. They were £20 each (I should have said ouch not each!) got tem home and BINGO they were just as bad as the original ebay ones only twice as much!

So back I went to the store with my camera and laptop complete with card speed tester and demonstrated the problem. They were very sorry and swapped it for a SanDisk 95MB/s EXTREME after testing several cards in the camera and laptop. It turns out that the EXTREME is just as good as my original 30MB/s ULTRA card.

In fact BOTH EXTREME and ULTRA cards write at 15MB/s but the EXTREME cost £40 OUCH (it came in a black box too, maybe thats why it was so expensive?).

They only had one in the shop and let me have it for the same price as one of the ULTRA cards I bought the day before but very kindly gave me £20 back.

As of 03/May/2013 I am awaiting a reply from SanDisk as I have downloaded their card testing software and tested and logged all my available cards and sent them a report. I have also reported the ebay seller to ebay and the seller suggests sending them back for a replacement, but what am I going to get back?
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