Memory Cards—A Basic Overview

Memory cards are the photographer’s digital equivalent to film. The most common types of memory cards include SD (Secure Digital, up to 2 GB of capacity), SDHC (High Capacity, up to 32 GB), SDXC (Extra Capacity, up to 2 TB), and UHS (Ultra-High Speed) cards. Two factors determine how memory cards are rated. Speed rating measures the maximum reading and writing transfer speeds to and from the card in megabytes per second (MB/s). Class rating measures the minimum sustained speed needed to maintain an even rate of data transfer onto the card (particularly important when shooting hi-def video). Class 2 cards have a minimum transfer rate of 2 MB/s, while Class 10 cards transfer data at a minimum of 10 MB/s. UHS Speed Class (Ultra-High Speed) appeared in 2009 and utilizes a new data bus, so UHS memory cards are not compatible with non-UHS devices.  SanDisk’s recently released UHS-2 cards offer write speeds of up to 250 MB/s or faster. Note that performance may vary depending on your particular host device. Check manufacturer’s specs for your specific camera. A card’s capacity is designated in gigabytes (GB) or terabytes (TB) and refers to the amount of data a particular card can hold.


When selecting a memory card, purchase only quality, reputable brands such as SanDisk or Samsung. Because this is your ‘film’ equivalent, you don’t want to scrimp just to save a couple of dollars. At the same time, they can get very pricey, and there is no need to buy the most expensive card. Buy memory cards from reputable dealers only, and beware of counterfeit cards. Most manufacturers offer some kind of warranty. SanDisk offers a limited two-year warranty on its products, while the Samsung 64 Pro Plus offers a ten-year limited warranty. Keep in mind that warranties are no guarantee that a card won’t fail—and should it fail, only the replacement of the product is covered. Loss of images can still occur. SanDisk claims its cards have a Mean Time Before Failure (MTFB) of 1,000,000 hours.

Like film, precautions must be taken when using and storing memory cards to avoid the corruption of data or loss of images. When using a memory card for the first time, it should be formatted for your particular camera (See owner’s manual). Be sure your camera is turned off before installing or removing the card to prevent accidental data loss. A small lock switch on the side of the card allows you to prevent the accidental deletion or overwriting of data. Do not touch the gold contacts on the back of the card, as this may cause corrosion and interfere with the transfer of information. Do not fill the card to its maximum capacity, as this may corrupt data and cause the loss of data (a mistake I have personally experienced). Avoid exposing memory cards to extreme heat or cold. Store them in their supplied case, or a quality memory card wallet, like the Pelican 0915 Memory Card Case (purchased separately). If you do happen to lose data on a card, there are several fee-based online recovery options available, including DriveSaver Data Recovery.

When downloading photographs to the computer, I prefer to remove the memory card from the camera and insert it into the computer’s SD slot. Properly eject the memory card before removing it. If your device doesn’t have an SD slot, you can tether your camera directly via the camera’s supplied USB cable. Be sure the camera battery has enough charge to complete the process. Your third option is to purchase a memory card reader. I’m a minimalist in everything I do, so the last thing I want to do is carry around another piece of gear, especially when traveling. Unless it is your only option, spare yourself the expense and additional hassle of a card reader.

Redundancy is king! Backup your images to at least two devices before erasing them from the memory card. Please note that erasing a card does not remove protected images, whereas formatting deletes all images, including protected images. It is recommended to format the card periodically to optimize performance.

Please contact me with any comments, questions, or suggestions. I’m wishing you an enjoyable Summer. Until next time, happy image-making…


Leave a comment