At ThinkCamera we often get asked “how safe are my pictures?”, “if I drop my memory card in a puddle is there any hope for recovering the files?” and “which is tougher secure digital or compact flash?”. OK, that last one is usually somebody saying “don't buy a camera that takes SD cards because they are fragile”. Well, we like to base our advice on facts rather than guesswork. Besides, it's Friday and I want to break something.
About the test
First of all, the science bit. We took a couple of SanDisk Extreme III memory cards. There was one compact flash card and one secure digital. We filled them with a variety of files - plenty of jpegs, some raw files from various different cameras and a 70MB layered Photoshop file. A total of 917.2MB on each 1GB card.
After each test we put the cards in a SanDisk reader and checked every file. We ran a slideshow of all the jpegs directly from the cards and opened all the raw files and the PSD file in Photoshop. This last part was important because even a tiny amount of damage to raw file will render it unreadable by Photoshop - often it is possible to browse the thumbnails but the raws will be damaged beyond use. Then we formatted the cards, put them in a camera and checked we could still take pictures. If all this worked then we formatted them again, loaded up the original data and put them into the next test.
SanDisk's website boasts that these cards are “built to work under the most challenging conditions”. Let's see.
Washer Dryer
You know the scenario - you come in from a hard day's taking pictures covered in mud and sling your clothes straight into the washing machine. As you are relaxing with a beer, looking at your pictures on the computer you realise - you had another memory card with you, and it's still in your jeans which are just starting the spin cycle.
To simulate this, we took some jeans, dropped the cards in the pocket, chucked them in the washing machine and set it for a nice 40 degree wash with long spin cycle. When the cards came out we noticed they were a little wet and didn't want to risk them near any electronics. So of course we threw them straight in the tumble drier.
Result:The compact flash card was fine all data readable, and the card still works perfectly. It also has a lovely lemony fragrance and a different kind of bluey whiteness we think you'll like...
The secure digital also looked fine from the outside but reading it on a computer gave a different story. None of the data was readable and the card wasn't even recognised by a PC or Mac. We tried it in a couple of cameras and they both gave errors and were unable to format the card - it is toast. We'll ask SanDisk to take a look at the card and see if the data is recoverable. We swapped to a different SD card for the following tests - yeah we never learn.
Extreme temperatures
Well, the spec sheet says that these cards will work from -25 celsius to +85. That's probably just as well if you want to use them in Canada in the winter and the Sahara in the summer. It's a hot summer here - but not that hot. Or cold.
So... we took the cards and dropped them into a plastic pot of water and put it in the deep freeze. -19 celsius for 15 hours and somewhat unsurprisingly we now had memory cards in the middle of a solid block of ice.
Of course we needed to get them out and smashing the ice might damage our data - so we chucked the ice into a pan over some boiling water. It was tempting to put them in a pan of water but that would exceed 85 degrees and besides it would have been harder to take pictures.
I'm a bit hazy on the physics here and exactly what temperature they reached but they were in a steamer for the ten minutes it took the ice to melt plus a couple while I looked for something to get them out with. When they came out they were very hot to the touch.
Result:at first it looked worrying. All files browsed OK but the raws on the compact flash card wouldn't open in Photoshop. I copied the data off the card and could open them easily from the hard drive. I checked the card again and it was fine. I'm going to put that one down to moisture on the contacts or the fact that the card was burning hot when I put it in the reader. SD card worked perfectly (though I left that one slightly longer whilst I was messing with the CF so it will have cooled a little). This is interesting because I would expect the freeze thaw test to be tougher on the card than a washing machine but the SD passed this with flying colours.
Crushing
Anybody ever left your memory cards on the road and accidentally driven over them? No, didn't think so - but let's see what happens if you do.
For this test we chose a Saab 9-5 estate car. This weighs a little over 1.5 tonnes. We put the cards on a rough concrete path and, err, drove over them. A couple of times. Then we realised that the exposed contacts on the SD card had been facing upwards and so might have been protected by the tyre. So we flipped it over and ran over them again. The cards got pretty dirty doing this so we washed them in hot water and washing up liquid before putting them in the card reader.
Result: Well, both cards got pretty badly scuffed in this one. It wasn't just the weight of the car that did the damage but the roughness of the path that put big dents in the plastic housing of both cards. Amazingly the compact flash card survived this harsh treatment. All files are readable and it is still usable in a camera.
Sadly the same isn't true for the SD card. It looks no more badly damaged than the CF but it looks like the data is gone. The card won't mount on my computer. I have tried it in 3 different cameras and all of them say it is faulty and are not able to format it. It seems these aren't quite as tough as compact flash cards after all.
Verdict
Memory cards are tough - these Extremes from SanDisk area a lot tougher than even we imagined. To be honest, I wasn't surprised when there was a “stutter” with the CF card after freezing and boiling it. I was surprised when it came back to life and now works perfectly. I was amazed that running over a compact flash card with an estate car didn't seem to do any damage. It seems that SD cards may be a little more fragile than CF cards as both a normal domestic accident and a pretty stupid incident with a car were enough to render and SD card useless.
I'd be happy to class SanDisk Extreme Compact Flash cards as “plenty tough enough”. SD should stand up to normal use (like freezing in a block of ice all night) but don't try them in the washing machine - or under a Saab.
It's interesting to note that any of the tests we did would have completely destroyed a hard drive. If you are going on holiday and want to make sure your data comes back in one piece it looks like you'd be better buying more memory cards than investing in a hard drive backup device.
Thanks to SanDisk for being good sports about this. Naturally we didn't tell them what we were going to do with their cards when they sent them in but can we have some more please? A couple of our SD cards appear not to work too well…
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