SD cards are vital components of photography and videography. SD stands for Secure Digital (not to be confused with SanDisk, which is a brand of SD card). SD cards are memory cards that store your pictures and videos. Although there are other memory card types available (such as CF Cards), SD cards are pretty standard.
What to Look for in a Memory Card?
The most important aspects to look for in a memory card are size (physical form factor and how much data it can hold) and read/write speeds. Not all SD cards are created equal so in this next section we’ll take a deeper look into SD cards, so you’ll know which one to purchase.
What Does SD, SDHC, SDXC Mean?
There are 3 categories of SD cards based on their capacity/storage size.
| SD (Secure Digital) | 512 MB to 2 GB |
| SDHC (Secure Digital High Capacity) | 4 GB to 32 GB |
| SDXC (Secure Digital Extended Capacity) | 48 GB to 128 GB |
What Size Card Do I Need?
Physical Size
SD cards come in a variety of physical sizes such as standard, miniSD, and microSD. Standard SD cards are the largest of the bunch, measuring 32 x 24 x 2.1 mm and weighing about 2 grams. Many DSLRs and mirrorless cameras use standard sized SD cards.
MiniSD cards are smaller than standard SD cards and measure about 21.5 x 20 x 1.4 mm and weigh about 0.8 grams. MiniSD cards were originally designed for mobile phone use, but most mobile phones nowadays use the smaller microSD cards.
MicroSD cards are the smallest SD card, measuring 15 x 11 x 1 mm and weigh about 0.25 grams.
If you only have mini or micro SD cards there are adapters available to convert them to standard SD card size. But it’s recommended to just get the standard SD card size in the first place if you can.
Storage Size
The SD card storage size required for your photo and video files depends on a number of factors such as the resolution or compression format that you choose for your images and videos. Your camera manual can help to clue you in to how big a card you need by providing charts that indicate an approximate number of images/videos you can take at specified settings for specified card sizes.
What do the Different SD Classes Mean?
In addition to storage capacity, SD cards vary in their read and write speeds (how fast data can be written to and read from the card). The different classes help to identify the speed of the card. UHS stands for Ultra-High Speed and is available on some SDHC and SDXC cards. There is also a newer speed class called video speed class that was created from a demand for high resolution and high quality video recording.
| Minimum Write Speed Performance | Speed Class | UHS Speed Class | Video Speed Class |
| 2 MB/sec+ | 2 | ||
| 4 MB/sec+ | 4 | ||
| 6 MB/sec+ | 6 | V6 | |
| 10 MB/sec+ | 10 | UHS – 1 | V10 |
| 30 MB/sec+ | UHS -3 | V30 | |
| 60 MB/sec+ | V60 | ||
| 90 MB/sec+ | V90 |
Note that the listed speeds in the chart above are the minimum write speed performances. Class performance can vary among brands. One brand’s class 6 can be faster than another brand’s class 10, so check the actual speed specifications on the card’s packaging.
The maximum read speed is usually listed straight forward on the card label. For example, it will say 45 MB/s, which means the card can read 45 Megabytes per second.
Video recording requires high sustained write speeds, so it’s not recommended to use anything below a UHS-3 speed class or v30 video speed class. A card that is too slow will only be able to record for a short period of time before producing an error message and stopping recording.
I like to envision this concept with the I Love Lucy chocolate packing scene where Lucy must wrap chocolates as they come down a conveyor belt. Think of the chocolate as information coming from your camera, and Lucy as the SD card processing the information. At first, Lucy managed to wrap a few chocolates just fine, but as more and more of the chocolate came quickly down the conveyor belt, she wasn’t able to keep up. Similarly, if your SD card doesn’t have a fast enough write speed, it won’t be able to process the information fast enough and there will be an information overload, the card will error out, and recording will be stopped.
Which Brand of Cards Should I Buy, and Does it Matter?
Different brands offer different levels of reliability. Further, different brands have different performances among the classes, so branding does matter. Lexar and SanDisk are the most trusted SD card brands. However, be wary of knock offs that may be labeled as SanDisk or Lexar but instead are cheap rip-offs. If the price seems too good to be true, it probably is. So, make sure you buy from a reputable dealer like B&H Photo or Amazon (from Amazon itself and not a third party vendor).
How Long do SD Cards Last?
Of course, there is no definite answer as to how long an SD card will last, and it is subjective based on a number of items such as the brand of card, how often it is used, what physical conditions it’s placed in, etc. Occasionally, the card might even be dead right out of the package. So always make sure to test your card before shooting important events.
Generally, the SD card connectors are said to be the weakest part of the card and are estimated to withstand 10,000 insertions/removals into and out of a camera or card reader.
Additionally, the individual memory blocks in standard memory cards only have a limited number of times they can be written to before it fails. It’s estimated that the sectors can last at least 100,000 program/erase cycles (number of times data is written to the card).
SD card manufacturers have implemented wear leveling algorithms so that data is put on different sectors of the card to balance the “wear” across the memory card. There are also algorithms to automatically map out memory sectors that fail. Even with these advances, the general consensus seems to be that after 2 years it’d be a good idea to stop using that card in regular rotation as it is more likely to fail.
Honestly, memory cards are pretty durable. As seen with Project Space Planes, apparently SD cards can survive being launched into space, fall back to earth, and still be fine. Or more commonly, many people have reported that their SD cards survived a turn in the laundry wash cycle. In any case, here are a few tips to get the most out of your memory cards:
Tips for Using and Caring for Memory Cards
1. Always have more than one card.
It’s always good to have a backup in case your primary card fails or gets full from all your amazing videos.
2. Use dedicated cards for each camera.
Avoid using one card for multiple cameras. Instead, keep specific cards for each camera. Using a card between different cameras can cause data corruption.
3. Bigger may not always be better.
The Lexar website mentions that using higher capacity memory cards may reduce the life of your battery, though it is minimal. Additionally, renowned cinematographer Shane Hurlbut mentions on his blog that he likes to use smaller cards so that he is forced to change out the card and at that time will let his camera rest to prevent overheating. Also, if a card does become corrupt, less data will be lost on smaller cards.
4. Don’t max out your memory card.
There have been multiple reports that errors occur if you push your card to the limit and fill up the card completely.
5. Have patience.
To avoid corruption, make sure the camera has finished writing to the card before powering off. Similarly, when removing the card from your computer, make sure you “Eject” or “Safely Remove” prior to physically removing the card. This prevents corruption because it would ensure data was not in the process of being transferred when you rip the card from the computer port.
6. All may not be lost if you accidentally delete data or your card becomes corrupted.
If your card becomes corrupted or you accidentally delete data, check if the card manufacturer offers data recovery. Some companies, such as SanDisk, have been known to offer free data recovery software with the purchase of certain cards. If you accidentally delete data, the first thing to do is to stop shooting! If you continue to shoot, the data may be overwritten and lost forever. The next step is to see if the recovery program is able to retrieve the lost data.
7. Format your cards.
Occasionally format your memory card to prevent the card from corrupting.
8. Get a card holder/wallet to keep track of your cards and to protect them from damage.
Memory cards, especially SD cards, are pretty small which means easy to lose. In the hectic scramble to set up your gear and capture the perfect shot, it’s relatively easy to misplace cards, especially if you throw them haphazardly into your pocket. To keep things organized you can store your cards in a wallet clipped to your bag or belt so that they’re easily accessible but less prone to getting lost. Pelican is a very popular brand for protecting camera gear as they are known for their durability, and they offer memory card holders as well.
9. Use the card lock
Once you’re done with an SD card you can ensure the contents are kept protected by switching the write protect switch on the card. This prevents any data from being written to the card as well as prevents data from being deleted.
Formatting Your Memory Card
Formatting the memory card in camera sets up the card’s directory, file structure, and folders, etc. so that it is specifically suited to the needs of your camera. Therefore, you should always format the card in camera as opposed to on a computer. Formatting will delete all information from your card so make sure you have saved your pictures and videos elsewhere before formatting.
When to Format?
- card is brand new
- card was formatted by a computer or used in a different camera
- card is full with images or data which can be deleted
- card related error is appearing on screen
Why Format?
Formatting ensures optimal performance between your camera and memory card. When you go to your computer and view and edit content from your card, your computer may leave hidden files on your card that aren’t deleted when you do an erase all. Even the process of erasing leaves its own file artifacts that can build up over time and eventually cause the card to fail. Formatting the card helps to clear out these file remnants.
