What is the best memory card for a DSLR?

It’s nearly Christmas and I’ve asked for a new memory card for my DSLR, but which one? I’m no techie, but I’ve done some reading up, and hopefully this entry can help other people with their decision.

Memory cards might be boring but they matter! And you don’t need to buy the most expensive one to get the best out of your camera, either… So I think the real question to ask is ‘what is the best memory card for ME?’

I’m only looking at SanDisk because they’re priced well and cover a broad range of different specs, and the large consensus is that they’re very, very good. That’s one thing sorted, at least!

The main things to look for in a memory card

There are two main assets of a memory card; its speed and its capacity. What you look for/want will depend on your camera and what you use it for. The price will vary a lot on these two aspects as well; generally speaking if you double the speed OR capacity of a memory card, you’re almost doubling the price. Double both and you’re looking at 4 times the amount!

Look for speed if…

You’re a sports or wildlife or action photographer, for example, where every millisecond of the scene is important, and so you hold the shutter button down like it’s a machine gun (ESPECIALLY if you shoot in RAW whilst doing this or if your camera has a lot of megapixels).

Look for capacity if…

You’re a traveller, for example, and you don’t have access to a computer from one week to the next to move your files to. Or if you shoot in RAW on a large 20+ mega pixel camera and/or you need to take LOTS of photos in any one session (like at a wedding), or if you’re really bad at remembering to take the images off your memory card onto your computer :).

Look for both if…

You’re a travelling sports photographer ;) Or if you’re going to take reams and reams of action photos where you want to capture every millisecond of every minute of every hour! Okay, so joking aside, if you plan to take lots of frames per second using a large file size over an extended period of time. You could be covering a whole day of sporting events with your brand new pro DSLR, for example.

It’s likely that you’ll want a little bit of both, to be honest. Generally speaking, though, you’re more likely to benefit from a larger capacity memory card than you are a fast speed one (unless you fit the criteria above); and you probably won’t need the top end of both.

Something important to remember

A memory card’s performance will differ with each camera. This is because the speed at which your images are written to the memory card initially depends on the speed of your camera’s processor. Therefore there’s NO point in buying a really fast and expensive CF or SD card when your camera can never create data that quickly in the first place. For example if you:

–         Shoot in RAW or have fairly large file sizes but your camera cannot shoot many frames per second (roughly under 3), for                     example.

–         Shoot photos at a high rate but the files are small.

It’s useful to know the capabilities of your camera’s processor, how many frames per second it can take and what size the images are before buying a memory card. That way you can match up the abilities of the camera to the card and save yourself lots of pennies :). It’s very unlikely that you will need a memory card faster than 45MB/s or 60MB/s.

Here’s more detail…


In the SanDisk range there are many memory card speeds, measured in MB/s (megabytes per second). Basically this measures how quickly data can be transferred between the camera and the card (and to the computer).

In the comparisons below I am using a great chart done by http://www.robgalbraith.com/bins/camera_wb_multi_page.asp?cid=6007-12452&sort_col=card&sort_dir=ASC, which includes how many RAW files a Canon 5D mark iii can shoot in 30 seconds. The more images it can shoot the better the card. He’s reviewed other models too, so go take a look!

It is also useful to remember that a RAW file from the 5D mark iii is about 20MB and it can shoot at 6 frames per second. That’s rather a lot of data. The amount of data your camera can make for itself will depend upon the size of the images you’re taking and the burst rate of the camera.

15 MB/s, 20 MB/s and 30 MB/s – On a mark iii you can probably take about 10-30 in 30 seconds*. This is fine for cameras with smaller megapixel counts and/or don’t shoot many frames per second.

45 MB/s and 60 MB/s– This speed, unless you’re shooting quick action for extended periods of time, etc, is generally more than capable of meeting all your photography needs. A 60MB/s memory card can shoot up to 46 RAW images in 30 seconds with a mark iii*.

95 MB/s – The fastest you can get in the range. With my Canon 5D mark iii you can take between 55 and 64 RAW images in 30 seconds*. That’s pretty crazy stuff. The price reflects this, as they are generally double the price of a 45 MB/s. In my opinion most people don’t need to consider these ones.

*NOTE: These speeds also depend on whether you’re using an SD or CF card. These are all the speeds of a CF card, which is what a lot of DSLRs use. Most of the time you won’t need to look at both as your camera will only support one type (more on that later)…

CONCLUSION: The speed of card you’ll need can be loosely figured out by the processing abilities of your camera. If your camera can only take small sized images or does not have a very high burst rate (i.e. frames per second), then there is no great benefit from buying a faster card. Go for the mid-range ones and you’ll be fine – even with a good quality DSLR.


The number of photos a memory card can hold depends on the size of the photos. For example, my upgrade from a Canon 5D to a 5D mark iii meant that my memory card now only holds half the amount of photos it used to. This is why I want a new one :)

If your images are fairly small in size (for example you don’t shoot in RAW or your camera doesn’t have a large megapixel count); or you are very organised and good about moving your images from the memory card onto the computer; or you are selective with what photos you take, then capacity might not be so much of a worry for you. However, I don’t think you can go wrong with having some extra space, as you never know when you’ll need it!

The basic range is:

2GB, 4GB, 8GB, 16GB, 32GB, 64GB* and 128GB*.

On a 16GB memory card – the middle of the road – I could have about 1100 RAW images that were about 12MB each (as on the Canon 5D) or about 500 RAW images (at about 20MB) on the Canon 5D mark iii.(Interestingly you would have thought that the 16GB card could hold more than 500 RAW images on the mark iii, but that’s what it says on my display screen when the card is empty).

*NOTE: These sizes are usually only found in CF cards.

CONCLUSION: There’s no right or wrong answer in terms of what size memory card you need. It just depends on what you want to use your camera for, how many photos you’re likely to take in a session, etc, and the size of the photos you’ll be taking. You just want to make sure that you’re never in the situation where you’ve got to go back and delete photos in order to clear up some space!

SD vs CF

A lot of people won’t have to worry about the difference between these as most cameras will just hold one type of card or the other. And they’re both absolutely fine to use. But my Canon 5D mark iii, for example, can hold both an SD and a CF card. So what is the difference?

The most obvious difference is that SD cards are smaller and thinner. This could mean that you lose or break them easier. There are a few other structural differences, but I don’t think these are fairly significant in the grand scheme of things. They also do not have as large a capacity as CF cards.

The second most obvious difference is that SD cards are, on average, half the price of a CF card (I checked Amazon this morning). Why?? This really baffled me, especially as they seem to have exactly the same specs.

Lets go back to the chart again. A 95 MB/s Extreme Pro SD card (with a 16GB capacity) recorded 22 images in 30 seconds. The Extreme Pro CF card, which also writes at 95MB/s and has a 16GB capacity, recorded 56 images in 30 seconds. That’s a big difference.

CF cards, therefore, are faster than SD cards for the 5D mark iii, and in general, too. That could well explain why they’re cheaper…

Here’s another interesting thing for Canon 5D mark iii users… The Extreme Pro SD 45MB/s card (16GB capacity) recorded 21 images in 30 seconds. That’s only 1 less than the 95 MB/s and it’s HALF the price! My advice? Don’t bother getting the 95MB/s SD.

SO. When, like me, you’re faced with the dilemma of having both types of card to choose from, here’s my general conclusion:

For value for money and good performance, get a high speed CF card and a large capacity SD card for your mark iii.

In terms of price vs memory size (i.e. capacity), SD cards are much better value than CF cards; you can get a 32GB SD card for almost the same price as a 16GB CF card! So if a large capacity is your main priority, then just get a large SD card for your 5D mark iii.

Don’t worry too much about getting the fastest SD card. Save that for a CF card. The fastest SD scarcely matches a mid-range CF card in a mark iii, and the difference  in real terms between a 45MB/s and a 95MB/s SD card is negligible, and this is largely the case for the other speeds too. Spend your money on capacity instead, and the card will still be fast enough for most things.

For the CF slot, why not buy a higher speed card (like 60MB/s), which really can churn through more data. The capacity doesn’t need to be so much if you’ve got an SD too.

If I had to choose only one for the mark iii, it would be a medium-high capacity (32GB), fairly high speed (60MB/s) CF card.


Decide what you photograph and therefore what characteristics you need from a memory card.

Find out what your camera’s processor is capable of before buying a memory card and then match up their abilities. You will probably find that you don’t need the fastest speed and are able to save yourself a lot of money!

I hope this helps!

Please note that I am no authority on the subject; I write this as a layman for other laymen in the hope that it helps clarify things a little. Please do comment/correct if you think I’ve written anything that’s inaccurate!

Thanks also to this article :)


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