Choosing The Right Size of Memory Card

2012.09.05

The next essential purchase, after buying a digital camera and lens, if needed, is flash memory. Memory comes in difference sizes, speeds and types. The card-type obviously must match what is supported by the camera, so the most frequent question is: How much memory to buy?

How Much Flash Memory?

There are three factors which determine how much total memory is needed:

• How much you shoot? Consider a day of shooting, be it vacations, family event or a night on the town. How many photos to you see yourself taking at most? Remember that you may be limited by battery-capacity which can last less than 100 shots or thousands, depending on the model. Add to this how much video you expect to record.
• How often you unload? At home, you can easily offload images each day but when travelling this is not always practical. Count the maximum number of days you expect to shoot before you can offload full-resolution images to safe storage.
• Your camera, meaning the size of images and video, if applicable, it produces. Conservatively count 1 MB for each 3 megapixels of JPEG image or 1 MB of RAW file or 3 second of HD video. A better and more precise estimate can be calculated using a type found in your camera manual. This is how it looks in the Fuji X10 manual:

Note that even for a 12 MB camera like the X10, an 8GB can still take a whopping 1650 photos at the highest image quality but video is limited to 76 minutes. This represents an average of 5 MB per image.

After considering the above, estimating your memory consumption is easy. Taking 200 images per day at 5 MB each for a 3 week vacation requires 200 x 5 x 21 days, meaning 21,000 MB or 21 GB. Add a good 25% for safety and what you should get is about 26 GB of flash memory. Do not run to the store just yet! You must think about how many cards to buy first.

How Many Memory Cards?

Card capacities are so huge these days, up to 128 GB at the time of writing this, that it is possible to buy a single card with room to spare. The usual warning about a single card, is how much are you prepared to lose? With a single card, physical loss of the card is actually pretty hard since a single card rarely leaves the camera. What is most likely is failure.

Flash cards are actually incredibly resilient. Without moving parts, they can surface drops, stomps and even a trip in the laundry. However, every once in a while, a card fails. Choosing a good brand such as Lexar, Sandisk or Kingston makes this less likely but it still happens from time to time. If one card fails, you also need to keep shooting until you can buy another one, so we strongly recommend a minimum of 2 cards.

Two cards is certainly a good idea and more can be better. Remember that the smaller the cards, the less data is lost when a card fails. Too small cards are inconvenient because they interrupt shooting more frequently. For this reason, 2 GB is probably a good minimum for images only and 4 or 8 GB for people who record 1080p HD video.

A nice size is 4 GB per card because it fits perfectly on a DVD. If that seems tight, try 8 GB which fits on a slightly more costly Dual-Layer DVD. This makes it tremendously easy to back up images on the go. When a card gets full, burn it to disk. Actually, burn it twice for safety and learn how to backup digital media before you accumulate too much of it.

Now making a decision is easy. For needs of 21 GB for example, you can decide between six 4 GB cards, three 8 GB cards or two 16 GB ones.

SD, SDHC and SDXC Memory Card Differences

The most popular type of memory card is SD which has two revisions, one called SDHC and the other called SDXC. The difference between SD and SDHC is that SD is limited to 2GB while SDHC is limited to 32GB. If a camera supports SDHC cards, it supports SD ones too but not vice-versa. SDXC extends the size limit to a theoretical 2 TB or over 2000 GB. It also changes the file-system from FAT32 to exFAT. If a camera supports SDXC cards, it supports SDHC and SD ones as well but the converse is not true. Additionally, plenty of devices such as card-readers, laptops and photo-frames are not SDXC compatible yet, so keep this in mind when choosing memory cards.

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• Digital Photography