Choosing the Best Memory Card For Your Digital Camera
Which brand of memory card should I buy? Does it make a difference? How big of a card do I need? Is one large card better than multiple small cards? Does the speed rating of the card matter? This article was written to help answer these exact questions.
Cameras and lenses can be easily replaced, especially if they are insured. Those images from the three-week safari, your relatives wedding, or your summer long European tour, simply can’t.
Memory Card Reliability
The first thing to look at is the memory card itself. Most entry level and amateur level cameras use SD (Secure Digital) memory cards. Most professional and prosumer cameras use CF (Compact Flash cards). In general, Compact Flash cards tend to cost more, but offer higher read/write speeds, larger capacities and be less prone to failure than the Secure Digital Cards. This article will focus on those two card types.
While there are many manufacturers of memory card out there, the top tier, and the choice of the vast majority of pros, are SanDisk and Lexar. These are also the only two brands than Nikon tests with and recommends.
SanDisk claims a MTBF (Mean Time Before Failure) of over 1,000,000 hours – that’s almost 115 years before the average card fails. Their cards are rated for over 10,000 insertions. A sophisticated defect and error management system can rewrite data from a defective sector to a good sector on the fly. SanDisks built in Error Detection Code and Error Correction Code to try to recover corrupted data automatically.
The regular (blue) SanDisk CF card has an operating temperature range from 0°C to 70°C (32°F to 158°F). The Extreme III cards are rated with an operating range of -25°C to 85°C (-13°F to 185°F). They can withstand a shock of 2,000G (or about a 10 ft drop onto a concrete floor). Hard-drives can only withstand a 200-300G shock – a drop of less than 2 foot.
SanDisk quote less than 1 non-recoverable error in every 10^14 bits read (or one error for every 12.5 terabytes of data – or one out of every million 12.5Mb RAW files, or one out of every three million Fine JPEGs).
Overall the reliability from their Compact Flash cards is significantly better than even the best hard drives on the market today.
One important note: there are many fake SanDisk cards in the marketplace. Some of these are cheaper manufacturers cards with SanDisk stickers and packaging. Some are custom made with no quality control and put into SanDisk looking boxes. Our best advice, is to only buy from a reputable retailer like Amazon.com or BHPhotoVideo.com, and avoid buying memory cards that appear too cheap, are for sale on eBay, or some market stall while traveling etc – stick to reputable sources that are authorized dealers.
However, even with the best cards, errors do still occur. There are many, many millions of these cards in circulation today. Look at any DSLR internet forum, and you’ll find reports of lost images. Most of these you’ll note are either with cheaper cards, potentially fake SanDisk or Lexar cards, or caused by user error. If you remove the card from the camera before the camera has finished writing the data, you’ll lose images that the camera hasn’t completed writing. It’s very easy to accidentally format a card, especially if you use multiple cards. There are reports of certain software applications importing the images from the card, then the user deleting the card, only to find that the application only imported the thumbnail JPEGs that were embedded into the RAW image files, not the actual RAW image files. In virtually all these cases, most of the images are recoverable using data recovery software.
Bottom line, trying to save $20 on a memory card for a camera/lens system that costs hundred or thousands of dollars makes very little sense. If you stick with the top tier brands, memory cards are very, very reliable, and they are far from the weakest link in the typical users workflow.
Card Sizes: One Large Card vs. Multiple Small Cards
How much card space you need depends on what format you shoot (RAW files are significantly larger than JPEG’s), and how many shots you are likely to take between getting to a computer to clear off and backup the cards. If I’m traveling, I’ve usually got a laptop with me so I can backup my cards every evening. Some days I may only take a dozen shots, but it’s also not unknown for me to take several thousand shots in a day if I’m at an event with a lot of action.
On a Nikon D200 containing a blank 8Gb SanDisk card, the camera claims 480 shots are available for RAW shooting. This number is usually conservative, as the size of the RAW file varies. My Nikon D300 regularly gets around 700 shots on an 8Gb card using Lossless Compressed NEF files. If you switch the D200 to Fine JPEG, it shows 1,300 shots available. If you select RAW plus Fine JPEG, it shows 354 shots available. Your cameras manual will contain a table showing similar data for your particular model.
There are conflicting opinions as to if one large card is better, or if many smaller cards are. The argument for smaller cards is, that if your card fails or you drop your camera in the ocean, you lose less data. The argument for larger cards, is card failure is very rare, and largely recoverable. You also risk a much higher chance of dropping a card, getting it wet, sitting on it, losing it, accidentally erasing it, forgetting it or leaving it in your hotel room if you are managing multiple cards.
There are other things to consider also. Uploading to computer can take a long time – putting in one large card and leaving it to upload is a lot less work than swapping multiple smaller cards and uploading each one manually. A 4Gb size card is ideal if you back up to DVD – it’s the largest card size that will completely fit onto a DVD, making the back up a simple drag and drop.
There is no right or wrong answer, we’ve standardized on 8Gb Compact Flash cards – mainly because they hold a decent number of shots and usually offer the best price per gigabyte. I’ll carry up to ten of them with me when I’m traveling. As larger cards become more common and prices drop further, we’ll go to larger sized cards. The most important thing is to make sure you have enough memory card space to last you until you can upload them to a computer – it’s better to have more than you need than not enough.
Card Speed: How Fast Do I Need?
Memory cards come in a wide range of speeds, and the faster the card, the more expensive. How fast of a card you need depends on a number of items:
Is how long it takes for the images to upload to a computer important to you? If you are uploading via cable from your camera, your upload speed is limited by the camera. If you are using a CF of SD reader, you are limited by the speed of that. For the absolute fastest uploads, use a card that supports UDMA (like the SanDisk Extreme IV’s, SanDisk Ducati’s, and Lexar 300x) in a FireWire reader. For example, the SanDisk Ultra II 8Gb card claims a 15 Mb/second read speed, so that would take almost 9 minutes to upload on an optimally configured system. The 8Gb Ducati card claims a 45Mb/second speed, so would take less than three minutes to upload.
Which camera do you use? The Nikon D200 does not support UDMA, so even though an Extreme IV is faster in it than an Extreme III, the card is much slower than it is in the D300 – the D300 can handle a much faster data transfer rate.
How likely are you to fill the camera buffer? If you shoot landscape or take several minutes to compose each shot, then you don’t need a fast card. If you are shooting non-stop action and taking sequence after sequence at 8fps, you’ll need as fast a card as possible. Cameras like the D200 and D300 have a big enough on board buffer to store about 17 shots if you are shooting RAW. Once you’ve taken a picture, the camera writes it to the memory card and erases it from the buffer as soon as it can. Once the buffer is full, the camera won’t let you take another picture until it’s written an image to the memory card and made room in the buffer. If you are using an Ultra II card in a Nikon D300, this means you may only be able to take a shot every 2-3 seconds when the buffer is full. If you are using a Ducati card, you may still be able to manage a couple of frames a second. Then if you stop shooting, the Ultra II may take a minute or so to get the buffer cleared and all written to the card. The Ducati card will allow the camera to write the images to the card and clear the buffer in seconds.
If you take your time to compose each shot, and upload speed isn’t important to you, then memory card speed isn’t important. If you are shooting action or sports and use a rapid frame rate frequently, then you want the fastest card, and camera, that you can afford.
Data Recovery Whether you’ve accidentally removed your memory card while the camera was still writing, deleted or formatted the wrong card, or the card has developed an error, it’s usually possible to retrieve some, if not all of the lost data.
The higher end cards from both SanDisk and Lexar come with their respective data recovery software packages on CD. SanDisk’s is called RescuePro, and Lexar’s is called Image Rescue. Both are reputed to be very effective. A third part solution called PhotoRescue is also widely used and reputedly better than both SanDisk’s and Lexar’s offerings, fortunately we’ve not had the need to find out.
In Summary
Your photos are infinitely more important than your camera gear. By selecting the right memory cards and taking a few simple precautions, you can potentially save yourself from losing irreplaceable photographs due to the unforeseen events that hit us all occasionally.
27/01/2012 22:34 | 
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