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Does your camera need a fast SD card?

Posted on 22 Feb 2013 at 17:47

To get a meaningful measure of the differences between SD cards, we therefore loaded a variety of cards into a DSLR and observed exactly how rapidly each one enabled the camera to shoot JPEG in continuous drive mode. (One of the cards was a microSD card used in an adapter – see SD flavours, below.)

We then switched to raw mode and repeated the test. The camera we used was a Sony SLT-A77, which produces raw files of approximately 24MB and JPEGs of around 5MB with standard settings. If your camera produces smaller files then you can expect a faster turnaround, but the relation between cards should remain the same.

The results

You can see the results of our tests in the graphs below. As we’d expect, continuous shooting performance was blazingly fast for the first few seconds of the test while the camera was able to make use of its buffer. Once the buffer filled up, the differing speeds of the various cards came into play. The shooting rate fell into a slower rhythm (with the odd hiccup), giving a clear indication of each card’s true data-writing performance.

Do you need a fast SD card?

It’s immediately obvious that our two top-end SD cards outshone the rest by far. In our JPEG test, once the camera’s buffer was full, class 4 cards dawdled for more than a second between shots – while the 64GB Kingston 233X and the SanDisk Extreme 45MB/sec each kept snapping away at more than three shots per second. Clearly, the faster cards offer you a much better chance of capturing the perfect moment.

With these installed, the camera was able to completely empty its buffer, ready to start shooting again, only six seconds after we took our finger off the shutter. Other cards were much slower: the class 4 SanDisk card took 25 seconds to catch up. Copying the shots off the card was faster too. There isn’t a perfect correlation between write and read speeds, but by using a USB 3 SD card reader, we were able to copy files from the Kingston 233X card at an average of 70MB/sec, while other cards offered less than a third of that read speed.

We saw similar results in raw mode – but the sheer volume of data caused even the fastest cards to feel sluggish. The fast Kingston and SanDisk cards achieved only 1.25 raw shots per second, with other cards taking between three and five seconds to capture each image.

Worth the price?

Our test camera had a large enough buffer to capture around 20 JPEGs or ten raw files at very high frame rates before the speed of the memory card became an issue.

If you use your camera mostly for stills and portraits, which you can shoot at a leisurely pace, it’s worth experimenting to see how many shots its internal buffer can handle. You may find your camera provides all the headroom you need, in which case there’s no point shelling out for a fast SD card.

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User comments


I'm not a photographer but I've always wanted to know the differences between all the SD card types, speeds etc and this article explains in really well. Thanks very much

By Chatan on 24 Feb 2013


Thanks for a good article with very useful info.

By cja4sun on 24 Feb 2013

MJPEG video

My wife uses a Panasonic FZ50 camera for her part-time videography. The camera records in MJPEG format in a QuickTime wrapper.

Class 4 cards are adequate for situations where there's little on-screen motion, but it stutters when she must pan. Class 10 cards eliminate that.

By RonJohn on 25 Feb 2013

Tablet/phone cards used for more than just media

"Many tablets and smartphones feature a microSD slot, enabling you to expand the internal storage – perhaps to accommodate a personal media library, or simply to download and install more apps.

Do you need a fast SD card? In this case, there’s often no need to splash out on fast media. A regular class 4 or 6 card that’s capable of recording HD video will also be fast enough to play it back."

This is fine if you're just using it for media files. However these days, many people supplement their tablet or phone's internal application memory flash drive space with external SD or microSD cards in order to install more applications into this space. In this case, using a slower card will delay the launch of any applications installed on that card. A faster card will give you faster app launch times. So depending on what you put on your external card, it can be worthwhile to opt for the faster card.

By storm311 on 25 Feb 2013

USB 3 Card Reader

What is the min. speed of the SD cards that will benefit from using an USB 3 reader (vs USB 2 reader)?

By Albert on 27 Feb 2013

how about MLC vs SLC?

I must say that your review, despite being 5 pages long misses the most important property of flash memory: namely, whether its NAND cells are single or multi-level cells.
Multi Level Cells are cheaper, but will severely (10-fold, give or take) reduce reliability of flash memory. Moreover the MLC’s have higher power consumption and smaller operating temperature range.
Most manufacturers somehow “forget” to mention whether their product is MLC or SLC. The only one indicator is the speed. The MLC NAND cells are always slower than SLC’s.
So, purchasing the SD cards with fastest transfer rates, will guarantee you the highest reliability as it will be manufactured using SLC technology.
For camera´s, the reliability does not matter so much, at worst, one will lose a picture or two, but if the purpose of SD card is storage expansion, then Single Level Cells are way to go.

By stasi47 on 28 Feb 2013

SD card size and speed querry

I have a 4gb class 2 SD card in my lumix camera and I recently purchased an 8gb class 10.
Why would the 4gb class 2 be faster? It is very noticeable when editing the pictures while still on the card.

By iggysmith on 16 May 2013

SD card size and speed querry

I have a 4gb class 2 SD card in my lumix camera and I recently purchased an 8gb class 10.
Why would the 4gb class 2 be faster? It is very noticeable when editing the pictures while still on the card.

By iggysmith on 16 May 2013

I have a Sony HX300 camera for which I purchased a Sandisk Extreme Pro 8GB 95MB/S CD card in order to speed up write times. After taking 10 frames the write time is the same as aslow class 2 card. Will you explain why please.

By HillClose on 25 Oct 2013

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For more details about purchasing this feature and/or images for editorial usage, please contact Jasmine Samra on


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