Now that digital photography has freed us from the tyranny of film, we can blaze away on high speed motor drive without the fear of running out of ammo. SD cards store thousands of images.
How SD Cards Work
SD cards (Secure Digital) are the modern version of film — a place to store latent images until they can be processed. Film does this with silver particles, light sensitive emulsions and chemicals. An SD card does it by storing binary code within the microscopic maze of a solid state (no moving parts) computer chip. The camera sends tiny electrical signals through gates into the micro chip where electrons are held until other computer-controlled electronic signals drag them out (uploading/downloading) — or overpower and erase them (formatting the card.)
It all sounds fantastic, if not magical, and rather fragile. It is wonderfully fantastic, but not fragile. SD technology is just Nature at the sub-atomic level. Binary language. Electron code. And it’s surprisingly durable and secure. Most SD cards these days are waterproof, shockproof, and X-Ray proof. They can’t — I repeat, can not — be erased by powerful magnets, either.
SD Card Durability Issues
If that isn’t enough to make you feel secure about your Secure Digital image storage, consider this: you can write, erase and rewrite to those cards 10,000 times before they become weakened, and even then you’ll need closer to 100,000 write/rewrites to negatively impact performance. In other words, your little SD cards should outlast your camera body and perhaps even you. To be conservative, figure on a 10-year life span — for the card, not yourself.
Not all SD cards are equal, but most are close. You can nitpick about brands, models, price and speed, but differences are so minimal that you might choose based on price. I’ve been shooting the several brands/types of SD cards for several years now without a malfunction.
SD Card Priority Concerns
The most important things to prioritize are these:
- Read speed
- Write speed
Read speed is the speed at which the SD card can import images as you take them. If you shoot RAW file bursts at high speed, you’ll notice the camera will quit and report that it is “writing to buffer.” That means the data you just captured is being run through the software for storage onto the SD card. The faster this card accepts data, the faster you can resume shooting. These days the fastest cards advertise a read speed of 95 megabites per second.
Reliability is just what it says and pretty consistent across the board. Samsung, SanDisk and Lexar seems to get consistently high marks, but individual cards from any brand can fail.
Write speed is the speed at which the card writes its saved information to your computer. Most write around 90 MBS now.
How To Protect Your SD Card Investments
A generous SD card warranty might seem like a nice touch, but buyer beware. Collecting on that warranty may require jumping through so many hoops that it’s not worth the chase. Besides, once the card fails, you’ve lost the images on it, and that’s usually a higher cost (perhaps impossible to replace) than the card itself. Online forums are full of horror stories from photographers trying to claim warranties on SD cards. Snoop around and make your own judgement.
Perhaps the best way to guard against needing to file a warranty claim is by using your cards correctly. Obviously, protect them from physical damage, but just as importantly, protect them from electrical damage. This means not removing them from camera or computers until they are finished uploading or downloading. Ideally you should turn your camera off before removing an SD card. Also erase files via the format control in the camera instead of individually with the erase button on on your computer.
What Size SD Card Is Best?
Now for some pragmatic SD card advice. Should you use 8, 16, 32, or 64 GB cards? The higher the number, the more images they’ll store. A 32 GB should hold about 915 RAW or 9,155 high quality JPEG images taken on a 10 Megapixel camera. A 16 GB will cut that in half and a 64 GB will double it.
Some shooters like the mass storage capacity of 64 GB. The more cautious prefer to NOT put all their photographic eggs on one basket, so go with 16 GB or 32 GB cards. That way, if one card is lost, broken or corrupted in some way, not all images will be lost. Searching for specific images on a smaller card is easier, too.
SD cards are so tiny and light that dozens could be carried without fatigue. Keeping track of so many would be the real issue. My approach is to use the fastest, highest quality 64 GB cards and upload them to my laptop and a backup portable hard drive at the end of each shooting day. That way, should I find myself in a shooting cornucopia, I can blaze away and capture more images without changing cards. I rarely, however, use more than half their storage space unless I’m shooting video.
SD cards are getting so reasonably priced (check this one on Amazon) that it might be worth taking many on a trip and keeping images on them until you get home. I’d still back up to a laptop and then a 2 TB portable hard drive (which is really inexpensive storage) for redundancy, but keeping cards full is a reasonable travel backup.
Not having to travel with 60 rolls of 36 exposure slide film has lightened Ron Spomer’s travel vest appreciably. He loves SD cards.