When choosing an SD card, one of the most important factors to consider is the card’s speed class rating. This rating gives you an indication of the minimum guaranteed speeds that the card is capable of. There are several speed classes for SD cards, with higher numbers meaning faster speeds.
SD Card Speed Classes
Here is an overview of the different SD card speed classes:
| Class | Minimum Write Speed | Use Cases |
|---|---|---|
| Class 2 | 2 MB/s | Standard definition video recording |
| Class 4 | 4 MB/s | Full HD video recording |
| Class 6 | 6 MB/s | 4K video recording |
| Class 10 | 10 MB/s | High bitrate 4K, professional photography |
| UHS Speed Class 1 (U1) | 10 MB/s | Full HD and 4K video recording |
| UHS Speed Class 3 (U3) | 30 MB/s | High bitrate 4K video, burst photography |
As you can see, the speed class gives you a basic indicator of the type of applications that card can handle. Higher speed classes support more data intensive uses like 4K video or rapid burst shooting.
Comparing SD Card Classes for Different Uses
Here is a more detailed breakdown of which SD card speed classes are best suited for different uses:
Standard Definition Video Recording
If you are shooting standard definition video which has lower bitrates, a Class 2, 4, or 6 card is sufficient. There is no need to get a faster card solely for SD video recording. The cards in these speed classes can easily handle the SD video bitrate with room to spare.
Full HD Video Recording
For recording full high definition 1080p video, a Class 4 card or higher is recommended. Class 4 cards offer minimum write speeds of around 4 MB/s, which is fast enough to avoid any bottlenecks or issues when recording full HD footage, even at higher bitrates.
4K Video Recording
To record 4K ultra HD footage, you’ll want a card that is at least Class 6 or UHS Speed Class 1. These have guaranteed minimum speeds of 10 MB/s, which is necessary to reliably record 4K video without running into speed issues. If you are recording high bitrate or high frame rate 4K, a UHS Speed Class 3 card is ideal for ensuring smooth performance.
High Frame Rate Video
If you are recording HD or 4K video at very high frame rates like 120fps or 240fps, you’ll require an SD card with faster write speeds. Look for cards rated at UHS Speed Class 3 or higher, as these have guaranteed minimum speeds of 30 MB/s which is necessary for smooth high framerate recording.
Continuous Shooting & Burst Photography
For shooting bursts of photos in rapid succession, you’ll need a fast SD card rated at UHS Speed Class 3. These cards can maintain write speeds of 30MB/s or higher, which enables shooting sequences of 20+ full resolution images in a second without freezing up your camera’s buffer.
Professional Photography
For professional or high megapixel photography, UHS Speed Class 3 cards are recommended. The raw images and large megapixel sizes require fast write speeds to quickly save each image. This allows professionals to maximize their workflow efficiency.
Recommended SD Cards by Use Case
Based on the speed requirements outlined for different use cases, here are some recommended SD card models to consider:
| Use Case | Recommended SD Cards |
|---|---|
| Standard Definition Video | SanDisk Ultra Class 4, Kingston Canvas Select Class 4 |
| Full HD Video | SanDisk Extreme, Lexar 633x Class 10 |
| 4K Video | SanDisk Extreme Pro, Lexar 1000x Class 10 |
| High Frame Rate Video | SanDisk Extreme Pro V30, Sony SF-G Series U3 |
| Burst Shooting | Sony Tough Series U3, SanDisk Extreme Pro V30 |
| Professional Photography | Sony Tough Series U3, Lexar Professional 1000x |
These cards offer the right balance of speed, value, and wide compatibility for excellent performance across different types of photo and video work.
Factors to Consider When Choosing an SD Card
In addition to the speed class, there are some other factors to weigh when deciding which SD card to buy:
Storage Capacity
Choose a card capacity suitable for your storage needs and recording times. Higher capacity cards are available up to 1TB now. Get more capacity than you need so you don’t run out at a critical moment.
Brand
Stick to major brands like SanDisk, Sony and Lexar. Avoid cheap generic cards which may have fake or exaggerated speed ratings.
Durable Design
Look for cards with durable builds for reliable performance. Features like water, shock, xray and temperature proofing help the cards withstand harsh conditions.
Warranty
Opt for cards that come with a manufacturer’s warranty in case you get a defective card. Warranty periods typically range from 1-lifetime years depending on card model.
Price
Cards with higher speeds, capacities and durability come at a higher price. Consider how you will use the card to decide if a pricier high-performance card is warranted or if a budget card will suffice.
Compatibility
Make sure the SD card is compatible with your device. Most are universally compatible, but double check speed class support and physical fit.
SD Card Speed Class FAQs
What is the fastest SD card speed class?
The fastest speed class currently available for SD cards is the UHS Speed Class 3 or U3 rating. This guarantees minimum sustained write speeds of 30MB/s.
Is UHS better than Class 10?
Yes, UHS speed classes are faster than equivalent numbered classes. So U1 is faster than Class 10, and U3 is significantly faster than Class 10.
Is Class 10 overkill for 4K video?
It depends on the bitrate of your 4K footage. For lower bitrates, Class 10 may suffice but it is typically recommended to use U1 or higher rated cards to be safe when recording 4K video.
What does V30 and V60 mean on SD cards?
V30 and V60 refer to the minimum guaranteed video write speeds for that card when recording at the highest quality settings. V30 = 30MB/s minimum, V60 = 60MB/s minimum sustained write speed.
Do I need a fast SD card for shooting photos?
It depends on your camera resolution and if you shoot bursts. Higher end DSLRs and mirrorless cameras can benefit from UHS-I U3 cards for fast shot-to-shot times when shooting bursts of RAW images.
Can a slow card damage your camera?
In most cases no it will not damage the camera, but it can severely limit functionality. Using too slow of a card may result in dropped frames, recording stopping unexpectedly, or very slow shot-to-shot times as the camera waits for data to save.
Conclusion
When choosing an SD card, understanding the speed classes is key to finding a card fast enough for your particular recording needs. The class rating system makes it easy to determine if a card can support video at different resolutions and data rates, as well as for handling rapid-fire burst image capture.
Aim for cards in faster speed classes than you think you need to ensure good performance and headroom for future use. And when in doubt, you can check the recommended uses for each speed class to see which type of card best matches your workflow. Taking these factors into account will help you select a high-performance SD card that won’t let you down!
