Memory cards for cameras

It’s been a while since I last wrote about camera accessories, hasn’t it? So, you’ve just bought a new camera? Then it’s time to choose a memory card to store all your photos. And this is where things can quickly get confusing, especially if you’re not used to all the technical terms. Between SD and CF cards, storage capacities, write and read speeds, speed classes, and plenty more, there’s enough to make your head spin! Don’t worry, I’ll walk you through everything you need to know about these small but essential electronic accessories for photographers. I’ll also show you how to understand the symbols on camera memory cards, so you can choose the one best suited to your needs. And if you want to go further, I also invite you to read our article on another camera accessory we really like: camera lens filters. It explains everything you need to know about these small accessories, which can be very useful in many situations.

When digital photography first appeared, almost every camera manufacturer had its own memory card format, which made things very easy to get lost in! Thankfully, over the years, manufacturers gradually moved toward more standardized card formats. Today, the two types of memory cards most commonly used in cameras are SD (Secure Digital) and CF (CompactFlash).

SD cards are the most compact option, even if high-end versions are now getting closer to CF-style formats in terms of performance. They are widely used in entry-level and mid-range DSLRs, bridge cameras, compacts, and mirrorless cameras.

CF cards stand out for their performance and speed. Their main drawback is their larger size, which takes up more space in the camera. Long known for being faster than SD cards, even if the gap has narrowed over time, they are mostly found in professional and high-end cameras.

CF cards were introduced in 1994. The CFast 2.0 standard can reach read speeds of around 600 MB/s. Since the early 2010s, the Nikon-SanDisk-Sony trio has also pushed the XQD format, which offers better performance than CompactFlash. It can reach a theoretical speed of up to 1 GB/s in version 2.0 thanks to PCI Express, although real-world speeds are usually lower. This is where CFexpress comes in. It has largely taken over from XQD in many recent high-end cameras, especially as some models originally designed for XQD have gained CFexpress compatibility through firmware updates. The standard has also evolved since its first versions: CFexpress 4.0 now uses PCIe Gen 4, with some Type B cards reaching much higher speeds than older CFexpress generations. Since 2019, several CFexpress formats have existed:

• Type A: compact, with one PCIe lane;
• Type B: the most common high-end camera format, with two PCIe lanes;
• Type C: larger, with four PCIe lanes.

Given their performance, CFexpress Type B cards can still cost several hundred euros…

In any case, your camera will determine the card format you need, so you won’t usually have much choice. Your camera manual or the manufacturer’s website will tell you which card format is compatible.

This is often the first thing people look at. But what exactly is storage capacity? It’s the amount of data a memory card can hold, and it is expressed in GB (gigabytes). As a rough idea, a 1 GB card can store around 100 photos of 10 MB each. Of course, everything depends on your camera’s megapixel count, because the more megapixels you have, the larger your files will be, but also on the recording quality you choose. The higher the capacity, the more data you can store, whether photos or videos. The downside is that if you store everything on one large card, you also increase the risk of losing a lot of files at once if something goes wrong. Storage depends on several factors:

• the number of files: photos, videos;
• their size: your photos will be larger if your camera has a higher-resolution sensor;
• the recording quality of your files: JPEG requires less storage space than RAW;

To choose the right storage capacity, ask yourself a few questions: how will I use my camera—daily, while traveling, or only occasionally, for a child’s show, for example? Will I be able to back up my photos regularly? Do I prefer several medium-capacity cards or one large card? Also keep in mind that, depending on the manufacturer and card type, some cards will be more reliable than others, but usually more expensive too.

After card format and storage capacity, let’s look at write speed. What does write speed mean? It refers to how quickly a card can record a certain amount of data. It directly affects how fast your images are saved to the card, so video recording and burst shooting are especially affected by write speed. That said, most cameras use a buffer precisely to avoid slowing down a burst too quickly because of a card that is not fast enough. Manufacturers also usually announce burst performance based on image quality, such as RAW or JPEG, rather than on a specific memory card.

On memory cards, maximum speed is usually shown in two ways:

• in MB/s. For example, a 60 MB/s card can theoretically write 60 MB of data in one second;
• in “x”: knowing that 1x = 0.15 MB/s, you simply have to convert it.

Beyond the technical aspect, write speed also has a direct impact on the price of a card, which can easily triple depending on its speed.

Read speed does not affect your actual shooting. It mainly determines how long it takes to copy your files to your computer. It depends on the characteristics of your memory card, but also on the type of connection you use with your computer.

It is often shown as a number followed by an “x.” For example, a memory card marked 400x is equivalent to a read speed of about 60 MB/s.

Another label appears on memory cards: the speed class. It corresponds to the card’s minimum sustained speed. In other words, the card should not drop below that level during continuous writing. Speed class is especially important for video, because video recording requires a steady data flow. For “classic” photography, the requirements are not quite the same, so write speed often matters more.

There are three main types of speed classes:

• Speed Class,
• UHS Speed Class,
• Video Speed Class.

The classic Speed Class is shown as a number inside a “C.” It ranges from 2 to 10. A Class 4 card, for example, guarantees a minimum write speed of 4 MB/s.

More recent, UHS Speed Class is shown as either U1 or U3: U1 guarantees a minimum sustained write speed of 10 MB/s, while U3 guarantees 30 MB/s. Be careful not to confuse this with the UHS bus type, such as UHS-I, UHS-II, or UHS-III, which refers to the card’s interface and potential transfer speed. UHS-II and UHS-III cards have a second row of pins, which allows for higher transfer rates than UHS-I.

The latest standard is Video Speed Class, designed especially for video recording. It ranges from V6 to V90, with V10 guaranteeing 10 MB/s and V90 guaranteeing 90 MB/s. In practical terms, here are the speed classes I recommend depending on the type of video you want to shoot:

• standard video: C4 to C10 or at least V6
• Full HD video: C6 to C10 or V10/V30
• 4K video: U3 or V30 as a safer minimum
• 8K video: V60 or V90

As you can see, for video quality above standard definition, you should ideally start with at least a C10 card, and preferably U3/V30 or higher depending on your camera.

Your choice of memory card, especially its format, will first be determined by the camera you plan to use it with. Most cameras accept SD cards, whether they are DSLRs or mirrorless cameras. SD has gradually overtaken CF and many other formats. MicroSD cards also exist, but they are more commonly used in phones, drones, action cameras, and other compact devices.

Among SD cards, there are several categories based on capacity:

• SD: up to 2 GB;
• SDHC (SD High Capacity): over 2 GB to 32 GB;
• SDXC (SD eXtended Capacity): over 32 GB to 2 TB;
• SDUC (SD Ultra Capacity): over 2 TB to 128 TB.

Be careful if you choose SDXC or SDUC cards: you need to check that your camera is compatible with that format, even if SDXC compatibility is now very common.

You also need to consider the file system, meaning how data is stored and organized on the SD card. SD cards use FAT12/16, SDHC cards use FAT32, and SDXC and SDUC cards use exFAT. For 4K video, for example, exFAT is usually preferable, because FAT32 is limited to files of up to 4 GB.

To choose your SD card, start by reading your camera manual. It will usually tell you:

• which card types are supported;
• the required write and read speeds;
• the maximum supported capacity.

Here is how SD card compatibility generally works:

• SD card: compatible with SD, SDHC, SDXC, and SDUC devices;
• SDHC card: compatible with SDHC, SDXC, and SDUC devices;
• SDXC card: compatible with SDXC and SDUC devices;
• SDUC card: compatible with SDUC devices only.

When it comes to write speed, there is no point buying a card rated at 300 MB/s if your camera cannot take advantage of that speed. That said, the way you use your camera should guide your choice. If you want to shoot high-definition video, you should choose a fast card.

SDUC cards are best suited to professional use or very high-quality video, given the ever-growing amount of content to store, such as 4K, 8K, VR, and more.

As you’ve probably gathered, you won’t choose the same card depending on your camera and the type of photos or videos you want to shoot.

Here are a few examples of cards I recommend, along with their technical characteristics. Of course, you can find equivalent options from other brands too:

• for photos with a bridge or compact camera, an entry-level card will often be enough. The SanDisk Extreme Pro 32GB Class 10 U3 offers an excellent price-performance ratio, with a typical price of around 15 euros and enough storage for many uses;
• if you shoot a lot, especially in RAW, and want a little more capacity plus shorter transfer times to your computer, the 64GB version is a better fit, with a higher transfer speed.
• for 4K or 8K video, the best option is to move toward the high end, for example with the Lexar 2000x.

To go further, here are some of the best SD cards as well:

• SanDisk Extreme PRO SDXC memory card (up to 170 MB/s, UHS-I, Class 10, U3, V30) — available from 32 GB to 1 TB of storage
• SanDisk Ultra SDHC/SDXC memory card (up to 120 MB/s, Class 10, UHS-I, V10) — available from 32 GB to 256 GB of storage, slower and lower-capacity but more affordable
• Lexar Professional 633x SDXC UHS-I card — available from 32 GB to 1 TB of storage

The brands that best combine reliability and speed are, without much doubt, SanDisk and Lexar. They are among the best-known names on the market. They also offer a very wide range, from beginner photographers on a small budget to professionals, or almost professionals, using a DSLR and needing very powerful memory cards. Feedback from photographers in general, and mine in particular, is very positive when it comes to these manufacturers and their products.

There are also other brands, such as Transcend or Kingston. But honestly, you can find almost everything you need with the first two brands mentioned, usually with a good price-to-performance ratio. That said, Kingston is becoming more and more visible and reliable. The brand also has solid expertise, since it manufactures RAM for computers too.

One piece of advice: avoid low-end cards, no-name store brands, or brands that are not well known at all. You may save a few dollars when you buy them, but you could quickly run into trouble if your card does not work properly or if you lose all your photos. You may regret not investing a little more from the start!

In addition to memory cards, a few small accessories can make your life much easier. They are easy to store in your camera bag. The link above explains everything you need to know to choose your bag.

To read the files on your memory card, you need a card reader. This small electronic device can be either internal or external. As for internal readers, not all desktop computers have one. Even on laptops, manufacturers often remove card readers to make the machines more compact. External readers simply connect to your computer through a USB port. You can use your computer’s built-in card reader if it suits you, especially in terms of speed. If not, and if you want to invest in an external card reader, here are two USB 3 models that offer strong transfer rates with most cards. I particularly recommend:

• SanDisk Extreme PRO SD card reader: it is compatible with UHS-II cards and backward-compatible with UHS-I and non-UHS SD cards;
• SanDisk ImageMate Pro multi-format card reader: its main advantage is that it can read many card formats, including SD, microSD, CF, and more.

A carrying case is a must-have accessory for safely carrying your memory cards everywhere and protecting them. Ideally, it should be:

• compact: easy to slip into a bag;
• rigid and durable: to protect your cards from impact;
• waterproof;
• designed to hold CF and SD cards: even if it is not essential, you might need both one day!

I particularly recommend cases for carrying hard drives and memory cards together, or the JJC case, both of which have a very good reputation. Some cases even have slots for camera batteries, which can also be useful.

Memory cards are fragile, so you need to take care of them. They are especially sensitive to water, but also to sun and dust. It is therefore important to store them properly, ideally in a carrying case, and handle them with care—no greasy fingers on the electronic contacts! If your card ever gets wet, all hope may not be lost. Wipe it gently with a soft cloth, then let it air-dry, especially not near a heat source. Wait at least one or two days before trying to read it, just to make sure it is completely dry.

Another tip: never remove your card from your camera, or your battery for that matter, before the camera is fully turned off. Power should not be cut before writing is finished, otherwise you risk losing data. So be patient—it only takes a few seconds!

Finally, one last piece of advice: it is better to have several smaller-capacity cards than just one very large card. If, for some reason, you lose your data, misplace a card, or damage it, only part of your files will be lost, not everything.

If you accidentally delete or lose photos or videos, or if an error message appears, don’t panic: there may still be ways to recover your files. Don’t take any more photos, remove the memory card from your device, and use data recovery software. Here are a few options that may be worth looking into:

• Recuva;
• ADRC Data Recovery Software Tools;
• SoftPerfect File Recovery;
• PC INSPECTOR File Recovery.

That’s it, we’ve covered everything about memory cards for cameras. You now know everything, or almost everything, about speed classes, storage capacity, formats, and more. I’ve tried to be as clear and complete as possible, and to give you enough information to help you make the right choice. Once you understand the basics of memory cards, everything becomes much clearer! If you’re interested in photo accessories, I also mention in this article all the accessories you need when you travel!

See you soon,

Written by Sylvain PONS

I've been passionate about photography since 2010, learning as I went along. Today, I dedicate myself to guiding others in their choice of camera gear and sharing a variety of tips to improve their photography skills.

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