SD memory cards for cameras. Who knew they came in so many types and sizes?

sandisk pro

I recently purchased a new Canon 6D and needed to switch from CF to SD memory cards. And I realized I had tons of research to do before buying the cards. Here’s what I learned:

There are several key components to naming and categorizing SD memory cards:

  • Capacity is a category indicating how much memory a card has. These cards generally specify exactly how much data they hold on the face of the card, so it’s not important to remember which capacity category holds what. What is important is that you know that these categories don’t correlate with quality or speed.
    • SD (Standard) cards hold up to 2 GB of data
    • SDHC cards hold between 2 and 32 GB of data
    • SDXC cards hold between 32 GB and 2 TB of data (that’s a lot!)
  • Speed Class describes the minimum writing performance of a card. In photography terms, speed class tells us how fast a card will record a photo that your camera has taken. The faster it records, the quicker you can take the next photo. The Speed Classes for SD cards are 2, 4, 6, 8 and 10. The fastest is 10 and 2 is the slowest. On the face of your card, you will see this number inside a large letter C.
  • Bus Speed, best as I can understand it, refers to how fast the pins on the back of the card read the data before recording that data inside the card.  The options here are:
    • Normal – for Speed Classes 2-8
    • Highspeed – for Speed Class 10
    • Ultra Highspeed/UHS I – indicated by 1 or 3 inside a U on the front of the card.
    • Ultra Highspeed/UHS II- indicated by 1 or 3 inside a U on the front of the card. Fastest bus speed.
    • It’s important to know that UHS II cards have a different pin array on the back from Normal, Highspeed and UHS 1 cards. You should only buy these cards if you know your device is compatible with them.
    • Also, you can use Normal or Highspeed cards in UHS 1 devices, but they won’t be as fast as the device’s potential speed.
    • The card type that works with your camera is specified on the camera manufacturer’s specifications page. Look on the specifications tab at this link  for info about the cards compatible with the 6D.

Photographers generally want the highest Speed Class and Bus Speed that will work on their cameras. For me, that’s Speed Class 10 and UHS 1. The SanDisk Extreme 16 GB is the card I chose. You can see the 1 inside a U and the 10 inside a C under the SDHC logo.

sandisk sd card


In addition to the speed class of 10, the face of the card indicates that the specific speed is 45 MB per second. Also, the capacity is 16 GB, which is why the card is a SDHC.

About that speed of 45 MB/s. This refers to the maximum or burst speed of a card and gives photographers an idea of how fast these cards will write if you are shooting on burst mode. You could go a lot faster on this speed. Just in the SanDisk Extreme SDHC line, I see speeds from 45 MB/s to 95. The difference is the price. The 95 MB/s 16 GB card is $35, whereas the 45 MB/s card is $18. And I’ve been quite happy with my 45 MB/s cards!

How about that capacity? Yes, I could have gotten something much larger than 16 GB. And no, I have not yet filled up a 16 GB card completely. This is my perspective: cards sometimes break or become corrupt. Would I rather lose 32 GB of photos or 16? For me, it’s better to switch cards once or twice during a shoot as insurance in case something happens to one of the cards. It’s better to lose some of my photos than all of them, right?

Mini & Micro SDs are smaller cards that only fit specific devices. Don’t buy them unless your camera calls for one specifically.

So, if you are in the market for new SD memory cards, you can now make an informed choice. And I hope the info was quite as boring to read as it was to research! 🙂