I have Canon 550D Rebel T2i and I am looking for a high speed Memory card. So far I have been using basic SD card but recently I have experienced it relatively slow while shooting fireworks at night.

I am looking for some suggestions about which one to buy.

Sandisk Extreme Pro transfers 95MB per second and Extreme Plus at 80MB per second. I want to know at what rate my camera transfer the data to card so that I can buy the card which supports upto that level. Don't want to buy Extreme Pro if my Camera transfers at data at slower rate.

Occasionally I do capture video as well so which SD card is more suitable for me, Pro or Plus?

Thanks in Advance

  • \$\begingroup\$ 8Mb is probably 80M? \$\endgroup\$
    – TFuto
    Apr 16, 2014 at 11:35

1 Answer 1


Just a side note: slowness during making night shots may be due to noise reduction...

The data transfer speed is easy to calculate. Take a picture of your choice (e.g. RAW with 12-bit, uncompressed - just an example), and see the file size of that. (Or average the sizes of the pictures you have made - or find the worst case size.)

Now, when you make pictures, you first fill up the internal buffer, and meanwhile start writing the files on the SD card. So you will have to know how many pictures you can make in a burts, before your camera slows down considerably. This you can test with any card, the slower the better, actually.

So let's say you have 10 MByte pictures, and your burst is 9 picture per second. (I am completely making these numbers up.) So your data transfer rate should be 10*9 = 90 MByte/sec. And you select a card that supports that speed, easy. (You should choose a little faster card than what your calculations shows, just to leave some time for filesystem manipulation, access times, etc.)

Now, beware. There are MANY counterfeit, fake, etc. memory cards which do not support the writing speed they advertise. E.g. Amazon is known to NOT be a reliable Sandisk/Kingston source... So test your card for writing speed when it arrives.

Now, if you want video, check your manual for data transfer rate specification, they usually say that you need 45 MB/sec or so, and you just need a card that supports it...

  • \$\begingroup\$ thanks for your answer. I was thinking to buy from eBay but not I am bit worried. Even on ebay SD cards are relatively cheaper then other sites. Any Idea what are the reliable sites to buy memory cards? \$\endgroup\$
    – Scorpion
    Apr 17, 2014 at 8:52
  • 1
    \$\begingroup\$ I was actually worried as well, so I went in a physical shop (Adorama the last time, but it can be any shop) so that you can buy a card, then verify at home, and if it does not perform well, take it back immediately - they must replace or refund you. \$\endgroup\$
    – TFuto
    Apr 17, 2014 at 12:10

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