Making Sense of Memory Cards

Selecting a memory card might seem like a complicated process, but knowing some key pieces of information can help make selecting the right memory card easy. In addition to understanding the different memory card formats and related terminology, videographers and phototgraphers must also consider their use case and workflow to ensure they choose the right technology to meet their needs.

Common Memory Card Formats

While many memory card formats have come and gone over the years, two formats have remained popular options for different types of shooters: Secure Digital (SD) and CompactFlash (CF).

Secure Digital is the most popular memory card format in the world today. SD cards can be found in all types of cameras, from point-and-shoot still cameras to handheld video cameras all the way up to professional DSLRs that capture images and video. The mobile version of SD cards are microSD cards. They adhere to the same technical specifications as their SD card big brothers but are designed for use in smartphones and tablets. As image capture devices have transformed over the years, becoming smaller and more portable, the microSD card has been adopted for use in new technologies like HD sports cams and drone cameras.

The second longstanding format is CompactFlash. CF cards are generally preferred by professionals for their physical durability and size, and are used in professional DSLRs and cinema cameras.

Understanding Memory Card Terminology

In addition to recognizing the different types of memory cards available, there are a number of symbols and terms that help identify the type of memory card, as well as its capacity and performance capabilities. When reviewing these details, it’s important to understand your use case and workflow to help determine which card is best for you.

  • Capacity: Like flash drives, hard drives, and solid state drives, memory cards have specific capacities, which are identified in gigbytes (GB) and labeled on the front of the card. The higher the capacity, the more content (photos or videos) you can store on the card. So if you primarily shoot still images while hiking or camping, you might not need a memory card with a huge capacity. But if you’re planning to shoot a lot of video content, you should opt for a larger capacity card.
  • X-Speed: A performance identifier adopted originally by Lexar and that has since been adopted by many card brands in the industry. The higher the number before the “X” speed symbol, the higher the performance of the memory card. Each “X” represents .15MB/s. For example, if you multiply an SD 2000x by .15MB/s you will get 300MB/s.

  • Performance: The speed at which your card is able to store or unload images, expressed as “read” and “write” speeds.

    Read Speed: How fast images are transferred off of a memory card to a computer.
    Write Speed: Write speed is how fast images are written to a memory card inside the camera.
  • Speed Class: SD cards have some additional symbols that can be found on the card label to define speed. Designated by the SD Association, a global association that sets industry-leading memory card standards for SD formats, speed class symbols show photographers the required minimum write performance. There are two kinds of speed indications regarding SD cards: Speed Class and UHS Speed Class.

    Speed Class: Designates minimum write performance to record video, ranging from Class 2 (slowest) to Class 10 (fastest).

    UHS Speed Class: Indicates how quickly visual content can be transferred onto the memory card. UHS-I enables maxium transfer speeds of 104MB/s while UHS-II enables maximum transfer speeds of 312MB/s. Within the UHS Speed Class there are two designations, U1 and U3, which represent 10MB/s and 30MB/s minimum write speeds respectively.

  • Video Performance Guarantee (VPG): This standard comes from the CompactFlash Association and is very similar to SD’s speed class. Today, VPG has two ratings that indicate the minimum write speed the card can perform, VPG-20 and VPG-65, with writes speeds of 20MB/s and 65MB/s respectively.

Emerging Memory Card Formats

In addition to SD and CF cards, there are a few emerging memory card formats that you might not be familiar with just yet, XQD and CFast, both published by the CompactFlash Association. It’s worth noting these new formats were created to replace the CF card format as it has reached maximum performance capabilities and cannot meet the intense write speeds today’s camera technology demands. In its current revision, 2.0, XQD cards have a theorhetical limit of 500MB/s. CFast in its current revision, 2.0, has a theorhetical limit of 600MB/s. Both of these card formts are ideal for 4K and beyond cinema cameras.

Questions to Ask When Buying a Memory Card

Now that you understand the different types, speeds, and classifications of memory cards, how do you determine what card is best for you and your needs? Here are a few questions to ask yourself before you purchase your memory card:

  • Type of photography: What type of photographs do you plan to take? Action shots, still shots, or even video? Understanding how you plan to use your memory card to capture images and video will help you decide what memory card features and performance are most important to you. Shooting stills such as portraits or landscapes doesn’t necessarily require fast write speeds. Adversely, capturing action, sports, or video requires fast write speeds to help eliminate missed shots or dropping frames from video because your card is writing slowly. Beyond write speed, opting for a faster read speed means you will be able to offload your content quicker, resulting in a more efficient workflow.
  • Image format: Do you shoot in JPEG, RAW, or both? RAW images take up more room on your card than JPEG files. Therefore, you will need a larger capacity card if shooting RAW images or RAW and JPEG images at the same time.
  • How much and how many: How long do you plan to shoot for? Answering this question will help you determine how much storage (capacity of the card) and the number of cards you will need. It’s recommended to always have at least one extra memory card on hand when shooting in case you deicide to shoot more than you originally planned. It’s always better to have too much storage than not enough!
  • Lastly, but not least, memory card readers: Investing in a solid memory card reader from a reputable manufacturer is key for post-production work. Buying the fastest card on the market won’t do you any good if you have a slow reader. If you have a USB 3.0 port, buy a USB 3.0 reader to take advantange of fast read speeds. It’s important to note that the difference between USB 2.0 and USB 3.0 can mean cutting download times down from hours to minutes. Downloading your content faster lets you start editing sooner, which in turn allows you to more quickly shift your focus back to shooting.

You now have all the information you need to purchase the best memory card for your camera and workflow. Any other questions? Comment below and we will answer them!

Adam Kaufman is the director of worldwide memory card product marketing for Micron Consumer Products Group. He leads a team of product managers responsible for industry-leading memory card and reader products. Adam spends his time working to help creators enable great content in an effort to streamline their workflow process.

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    • First I'd like to thank you for your excellent article. I have a few questions below that it would be great if you could answer!


      Question 1:

      A problem that happens now and then are corrupt memory cards. How can we tell how reliable the card is?

      For instance memory cards for industrial use often mention MTBF numbers, what kind of NAND they use (SLC/MLC), temperature range, resistance to shock/vibration etc.


      Question 2:

      Sometimes the question comes up if it is better to use one or two larger memory cards compared to several smaller ones. While having several cards means that you wont lose as many images if you have a problem with the card, more cards also means a higher probability of failure, at least if the failure rate is the same for the smaller and larger capacity cards. What's your opinion on this?


      Question 3:

      If you do have a problem with corrupt images on the card is it likely to be the card, the camera or the card reader? And what should you do if you have very important images on it?


      Question 4:

      You didn't mention it in your article but when selecting a memory card it should also matter what kind of throughput the camera is able to provide. A faster card will only be faster in the camera, if the camera is able to write faster? Is my understanding correct?


      Question 5:

      This related to both memory cards and USB flash drives. How long can you safely keep the images on the card, for instance when used as a backup?




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    • I would love to hear the answers to # 3 and 5

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    • Why doesn't this article include the most straightforward indication of a card's speed, Megabytes per second? It makes more sense to me, and I find it more useful.

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    • Thanks for the great questions! Here are Adam's answers:


      Answer #1:

      From a consumer standpoint, data like NAND type/configuration and MTBF (Mean Time Between Failures) isn’t readily available because hopefully it isn’t necessary. For the average consumer purchasing from a trusted retailer, sticking with reputable brands is the first stop, then check to see what kind of warranty is offered in case something happens. Lastly, looking at customer reviews (for example on Amazon’s product pages) is a good indicator. If there are a lot of reviews with very high ratings, that is a good sign you’re looking at a good product.


      Answer #2:

      The number of cards a photographer uses is really a matter of personal preference. Some photographers prefer to use one or two larger capacity memory cards so they don’t have to worry about switching out cards during a shoot and possibly missing out on some great shots. Others prefer to use multiple smaller capacity memory cards to safeguard against possible card failure, or even for organizational purposes. Personally, I like using one large card for an entire trip, that way I don’t have to worry about losing it, but that’s just me.


      Answer #3:

      Corruption can come from a number of things. It could come from the reader, it could be from a defect in the card, or even the camera. The best thing you can do is once you notice the corruption, stop using it immediately. Don’t format it. Don’t try to keep taking pictures with it. Put it in your pocket or bag and wait until you get home. If your card came with recovery software (Lexar Professional cards come with Image Rescue software), try using that to see if your images can be found. If that doesn’t work, contact the manufacturer and see if they can offer support. Lastly, look for a reputable recovery lab (Prosoft is a good lab) and see what they can offer. It can be expensive, but that is going to be the best, last option.


      Answer #4:

      You are 100% correct. The speed at which you capture images and video in your host device will only be as fast as the slowest component in your workflow. For instance, if you have a memory card that leverages UHS-II speeds, but your camera is only UHS-I compatible, your memory card will only work up to the fastest speeds for UHS-I.


      Answer #5:

      A good rule of thumb is 10 years. It also doesn’t hurt to check in over time by plugging your NAND based storage device into a camera, a reader, or a USB drive into your computer to ensure everything is functional. Regardless, storing important files on either type of product is safe and you shouldn’t worry. Another good practice is redundancy. Back up your critical files in more than one spot. If it’s really important, it doesn’t hurt to have it in a few locations for safety.


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    • I have a memory card I picked up on a great sale from Amazon that has 128GB. I'm using it in my camera and it allows roughly 3800 RAW files. The more I think about it, though, the more I think that might not be a good idea. I don't do video, so I don't need a lot of room. The downside is that there might be a tendency to not upload the images to a computer or storage device as frequently as I should. Thus, losing the card or the information could be a disaster.

      I think I might go to a few relatively small cards, ones that will allow, at most, a few hundred images (which would probably be more than I'd shoot in a day, anyway), and be safer.

      Thanks for the article to revise my thinking on this issue.

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