The SD Card Buyers Guide: Everything you need to know before you buy

Have you ever looked at the the front of an SD Card or the back of the packaging, and wondered that all those numbers, letters and symbols actually meant? While most people will instantly know that 64GB, 128GB or 512GB refers to the storage space on the SD Card, other letter combinations such as SDXC, U3 or V90 might not be as evident.

Before you just buy any random SD Card that a store employe or best list on the internet recommended to you, take 5 minutes to brush up on your technical knowledge so you know that you’re getting right card.

SD card vs MicroSD Card

When MicroSDs first came on to the market, they had noticeable performance deficits compared to standard SD Cards. They had less storage space, and vastly lower read and write speeds – but they were also just a third of the size of a normal SD Card. Today, despite their tiny size, the performance of MicroSDs are virtually on par with most SD Cards, both in terms of storage space as well as read and write speeds.

If you’ve asked yourself “Can I use a MicroSD in my Digital Camera, or Can I use a MicroSD adapter in my camera” – the short answer ist No. Its not recommended that you use a MicroSD (with an adapter) in your Camera, regardless if its a point and shoot, Mirrorless or DSRL.

sd card versus microsd card
A regular SD Card compared to a MicroSD Card (not to scale)

While the adapter for the MicroSD is made so you can use it on your card reader or computer, it’s not designed for constant use in your camera. The plastic adapters are cheap and flimsy, and tend to crack after a certain period of time – and they most likely slow down the write speed when inserted in your camera. You should only use a MicroSD in your camera, if your camera has a dedicated MicroSD slot.

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What do the symbols on an SD Card mean?

While every SD Card manufacturer will brand their SD Cards with their own labels such as Extreme Pro, Elite Performance or Pro+, every card will have virtually the same recognisable information on them. Once you learn how to decipher these codes, you’ll be able to instantly spot how good an SD Card actually is*.

When picking out an SD Card, there are 2 things that you need to pay attention to: Speed and Storage Capacity. In the simplest terms, the storage capacity indicates how many files you can save on the SD Card, while the Speed indicates how fast you can save files onto the SD Card, and how fast your camera or computer can read these files from your SD Card.

While the storage capacity is the easiest and most obvious thing to spot – parsing the speed data can be tricky at first. Let’s break down the symbols on the SD Card.

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Let’s start with the most obvious one – What does SD on the SD Card stand for? SD Card actually stands for Secure Digital Card. Since the introduction of the SD Card, more standards have been developed. SDHC stands for Secure Digital High Capacity. SDXC stands for Secure Digital eXtended Capacity and SDUC stands for Secure Digital Ultra Capacity. In essence, these four abbreviations denote the different capacity standards. With each new standard (SDUC was introduced in 2018), the SD Card will be able to hold more data.

sd card capacity format
Minimum Capacity>2 GB>32 GB>2 TB
Maximum Capacity2 GB32 GB2 TB128 TB

Picking out an SD Card with an SDXC or SDUC label on it basically assures you that the card is using a high storage capacity standard.

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Speed Class

Now this ones needs a bit of an explanation. Just like you can pick out SD Cards with different storage capacities, you can buy SD Cards with different speeds. What is generally meant when we talk about Speed on an SD Card is how fast an SD Card can write data onto the card.

SD card manufacturers will generally list a specific speed alongside the Class rating on the card. So that means you’ll see a number like 170 MB/s on the card next to another number encircled in a C (this refers to the speed class). If we look at the SD Card below – we can see that the 170 MB/s refers to the fact that the SD Card has a minimum sustained write speed of 170 Megabyte per second. We also see the C10 logo, meaning that the card is a Class 10 and has a minimum sustained write speed of 10 MB/s.

speed class data read speed sd card
Class 2Class 4Class 6Class 10
Minimum write speed2 MB/s4 MB/s6 MB/s10 MB/s
The different Class Speeds as defined by the SD Association

SD Card Speed is important for photographers, especially if you shoot with an DSLR in a high resolution RAW format. You want your SD Card to cope with the large Data Format and to save your photos as quickly as possible.

Ironically, every modern SD Card achieves write speeds of over 10MB/s, so its highly unlikely that you’ll ever purchase a card thats not a Class 10.

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UHS Speed Class

With the introduction of 4K video technology, the SD Association introduced a new speed rating called the UHS Speed Class – the Ultra High Speed Class.

The UHS Speed Class is broken down into two categories, UHS Speed Class 1 and UHS Speed Class 3. UHS Speed Class 1 supports a minimum 10MB/s write speed, while UHS Speed Class 3 supports at least 30MB/s write speed. The UHS Speed Class is denoted by either a 1 or 3 inside of a U symbol. Generally, 4K-capable devices will usually require at least a U3 rated SD card.

UHS Speed Class SD Card
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UHS Bus Speed

If you look closely, you can spot the little roman numeral I, II, III or the roman numeral I and express underneath it on the SD Card next to the capacity standard. This is the UHS Bus Speed, which indicates the theoretical maximum read and write speeds on UHS Speed Class rated cards. UHS-I devices have a maximum read speed of 104MB/s, whereas a UHS-II card has a maximum read speed of 312MB/s. UHS-III rated cards have a maximum read speed of 624MB/s while SD Express rated cards can read up to 3940MB/s.

UHS Bus Speed class sd card
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Video Speed Class

As the name implies, the Video Speed Class indicates the continuous Video writing speed. When indicated on the card, the Video Class Speed is abbreviated to V followed by a number – the video write speed in Megabyte. Video Speed Classes range from V6 up to V90, though only professional filmmakers need a card rated up to V90.

Video Speed Class SD Card
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Application Performance Class

Most commonly found on MicroSD Cards and newer SD Cards, the Application Performance Class is indicated on the Card either by an A1 or A2 symbol. The AP Class was introduced when using MicroSD cards as expandable mobile storage took off. Essentially the specification denotes the speed with which cameras, PCs and other devices can access the card: A1 means at least 500 write or 1,500 read accesses per second, A2 is significantly faster – with 2,000 write or 4,000 Read accesses per second.

Application Performance Class microsd
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Fake SD Cards

With the rise of online shopping portals like Amazon, Aliexpress, Alibaba and eBay – the lure to buy extremely cheap SD Cards has been on the rise. But more often than not, the cheaper the card, the less “real” it is. Because this is such an expansive topic – we’ve written a separate guide: How to spot fake SD cards – which tells you how to avoid being scammed, as well as checking if your SD Card or MicroSD Card is real.

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What SD Card should I buy?

When you’re looking at buying an SD Card for your Camera (or any other device) – generally we recommend that you avoid any SD Card under 64GB. Technology is advancing so fast and its getting cheaper and cheaper, theres no reason for you to buy such a small card.

Point and Shoot Cameras

If you’re looking for an SD Card for your point and shoot camera and maybe want to take some videos – theres no need for you to spend $80 on the latest “Extreme Pro Card”. Chances are you wont be taking 4K Videos and you wont be shooting RAW Format photos. Nevertheless,SD Cards are very cheap these days so theres no harm in a 64GB or 128GB with write speeds of around 90 MB/s.


Don’t buy anything under 128GB. Look for a card that has at least a write speed of 90 MB/s. If you are looking to shoot a lot of video, get a high storage capacity card (think 512GB) and one thats rated U3 and at least V30 so you can shoot and save 4k videos.

Action Cameras

Similar to the DSLR SD Card recommendation, getting a MicroSD card that has a U3 Rating and at least a Write Speed of 90MB/s is always a good idea. Don’t cheap out any buy anything under 128GB as your MicroSD card will fill up very quickly when shooting videos.

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What is an SD card used for?

SD cards are most commonly used in digital cameras and other electronic devices to store Photos, Videos and other digital files.

What is the difference between an SD Card and a Memory Card?

An SD Card is a type of Memory Card. Memory Cards come in multiple different form factors – but essentially work the same. All SD Cards are Memory Cards, while not all Memory Cards, are SD Cards.

Can I use a MicroSD card instead of an SD Card?

Yes, you can use an MicroSD Card instead of an SD Card if you use the correct adapter. It however is not recommended to use an MicroSD with an adapter in place of an SD Card as a storage medium for your camera.

What are the different types of SD Cards?

SDUC There are four main types of SD Cards: SD – Secure Digital, SDHC – Secure Digital High Capacity, SDXC – Secure Digital eXtended Capacity and SDUC – Secure Digital Ultra Capacity. Each type of SD Card denotes the storage capabilities of each card.

Which is better SDHC or SDXC?

When comparing SDHC and SDXC SD Cards, SDXC Certified Cards (Secure Digital eXtended Capacity) are “better” as they can have a maximum storage capacity of 2TB (compared to a max. storage capacity of 32GB.

The newest storage standard ist SDUC – Secure Digital Ultra Capacity – and was introduced in 2018. SDUC Cards are rated to store up to 128TB.

Do SD Cards work in SDXC slots?

Yes, SD Cards work in SDXC slots.

Do SD Cards go bad?

Yes, SD Cards can go bad after a certain amount of time. This is because Flash Memory has a finite lifespan. Each SD Card has a limited amount of write cycles (roughly 100,000 depending on the SD Card). SD Cards can also corrupt due to storage in high temperatures or rough treatment.

What is better Sandisk Ultra or Extreme?

Sandisk Extreme was released after Sandisk Ultra. Sandisk Ultra SD Cards have a slower read/write speed compared to the Sandisk Extreme Cards. Sandisk Extreme Cards also allow you to store 4k Videos on them compared to HD Videos on the Sandisk Ultra cards.

  1. […] larger capacity cards are great, don’t put all your eggs in one basket. SD Cards can and will fail, especially if they’re not handled with care or exposed to extreme temperatures. Always make […]

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