What is a Class 4 SD Card?
A Class 4 SD card is a type of SD memory card that has a minimum sustained write speed of 4 megabytes per second (MB/s) (Source). The speed class rating system was introduced by the SD Association for standardizing the minimum performance of SD cards based on their minimum guaranteed speed.
SD cards with a Class 4 rating are considered basic speed cards that are suitable for point-and-shoot cameras, lower resolution video recording, and other devices that do not require very fast write speeds. Some common uses and advantages of Class 4 SD cards include:
- Recording 720p or standard definition video
- Storing photos from digital cameras with 10 megapixels or less
- Running apps and storing data on smartphones
- Affordable pricing compared to faster speed classes
- Sufficient performance for typical everyday tasks
While Class 4 SD cards have slower speeds than higher classes like Class 10, they offer adequate performance for many general consumer uses involving lighter workloads. Their lower cost makes them a viable option when high read/write speeds are not essential.
History of Class 4 SD Cards
The Class 4 speed specification for SD cards was introduced in 2007 by the SD Association (SDA). It was designed as an upgrade over previous speed classes like Class 2, which had a minimum write speed of 2MB/s.
The SDA adopted speed classes as a way to help consumers identify cards that were optimal for certain applications. Before Class 4, previous speed classes included Class 2 (2MB/s minimum) introduced in 2003, and Class 6 (6MB/s minimum) introduced in 2006.
Class 4 SD cards have a minimum write speed of 4MB/s. At the time of introduction in 2007, this was considered a reasonably fast speed for recording applications like digital cameras shooting SD video. However, as technology advanced, even faster speed classes were introduced by the SDA, like Class 10 in 2009.
The evolution of SD card speed classes reflects the growing demands of devices and applications over time. While Class 2 and Class 4 were sufficient in the 2000s, modern devices require even faster speeds like Class 10 for HD video recording. However, Class 4 cards remain a popular affordable choice for less demanding uses today.
Technical Specifications
Class 4 SD cards have a minimum write speed of 4 MB per second according to the SD Association’s speed class standard (https://www.sdcard.org/developers/sd-standard-overview/speed-class/). This means they can sustain transferring data to the card at a rate of at least 4 MB/s.
Initially, Class 4 SD cards had a maximum capacity of 32GB. However, as technology has improved over time, Class 4 cards are now available in capacities up to 2TB. The SD Association sets standards for maximum capacities based on speed class.
Class 4 SD cards support common file systems like FAT32 and exFAT to store files in a way compatible with digital cameras, computers, and other devices. This allows the cards to be read across different operating systems and platforms.
Performance Comparison
Class 4 SD cards have a minimum sustained write speed of 4 MB/s, compared to 10 MB/s for Class 10 cards. However, the maximum write speed can vary greatly between individual Class 4 cards. Some may reach speeds of 20-30 MB/s, while others max out closer to the minimum 4 MB/s.1
In real-world usage for cameras and mobile devices, Class 4 cards can record 720p HD video and are fast enough for many applications. However, their lower minimum write speed makes them less ideal for recording 1080p HD or 4K video. The slower speed also increases save times and shot-to-shot delays compared to Class 10 cards.2
For high resolution photos and burst shooting modes, Class 10 cards provide faster shot-to-shot performance. The higher sustained write speeds also make Class 10 cards better suited for devices that generate a lot of data quickly, like high-end digital cameras and camcorders.3
Common Uses
Class 4 SD cards are commonly used in a variety of digital devices that require basic speed and performance:
Digital cameras – Class 4 SD cards provide sufficient speed for saving photos and videos from point-and-shoot digital cameras. The cards can handle the data transfer rates required for most consumer-level cameras.
Camcorders – Basic camcorders that record lower resolution video utilize Class 4 SD cards effectively. The cards offer adequate performance for HD video in standard definition quality.
Mobile phones – Many mobile phones, especially lower-end models, come with Class 4 microSD card slots. The Class 4 speed is enough for capturing photos/videos and expanding the memory for most basic phones.
Handheld gaming devices – Handheld game consoles that play casual games typically support Class 4 SD cards. The cards provide sufficient speed for game storage and saves.
Advantages of Class 4 SD Cards
Class 4 SD cards offer some key advantages that make them a popular choice for many users:
Cheaper price – Class 4 SD cards tend to be very affordable compared to higher speed cards. This makes them a great budget-friendly option for basic needs.
Suffices for standard definition video recording – The minimum write speed of a Class 4 SD card (4 MB/s) is generally fast enough to handle recording standard definition video. This makes them useful for basic cameras.
Compatible with most devices – Given their slower speed, Class 4 SD cards have very broad compatibility. Most cameras, mobile devices, and other gadgets that take SD cards will accept a Class 4 card. This versatility is a huge advantage, and they will often be seen in any grade camera, ranging from those used by beginners all the way up to advanced devices (source).
Disadvantages
Class 4 SD cards have some disadvantages compared to faster SD cards:
They have slower transfer speeds. Class 4 SD cards have a minimum write speed of just 4 MB/s. This means they will be noticeably slower than faster cards like Class 10 when transferring files like photos or videos. The slower speed can lead to buffering or lag times.
They are not ideal for full HD or 4K video recording. Due to the slower write speeds, Class 4 cards may struggle to keep up with writing large full HD or 4K video files. This can potentially lead to dropped frames or corrupted footage.
Higher capacity cards have even slower speeds. The advertised minimum write speed only applies to lower capacity cards, usually up to 32GB. Larger capacity Class 4 cards often have significantly slower write speeds than 4 MB/s, which exacerbates the speed disadvantages.
Buying Considerations
When looking to purchase a Class 4 SD card, there are a few key factors to consider:
Check device compatibility – Not all devices support Class 4 SD cards, so it’s important to verify compatibility before purchasing. Look at the device manual or specifications to confirm which SD card speeds are supported.
Capacity needed – Class 4 SD cards come in capacities ranging from 2GB to 32GB typically. Consider how much storage you need for your intended use case. Recording high resolution photos and video requires more capacity.
Impact on recording time – Due to the slower write speeds, Class 4 SD cards may reduce burst mode photo shooting speeds and video recording durations compared to faster cards. Check your device specs to understand the impact.
For example, according to this source, shooting 1080p video may be limited to around 10 minutes per clip when using a Class 4 card, whereas faster cards can record for longer durations.
Popular Class 4 SD Cards
Some of the most popular Class 4 SD cards come from top brands like SanDisk, Samsung, and Kingston. Here are some of the top models:
SanDisk Ultra 32GB Class 4 SDHC Memory Card – Offers decent performance at an affordable price. Capacity up to 32GB and read speeds up to 30MB/s.[1]
Samsung EVO Select 32GB Class 4 Micro SDHC – Budget-friendly option with good performance. Up to 32GB capacity and read speeds of up to 24MB/s.[2]
Kingston 16GB Class 4 Micro SDHC Card – Reliable performance at a low price point. Capacities up to 16GB and read speeds of up to 24MB/s.[3]
While most Class 4 SD cards max out at 32GB capacity, some models like the SanDisk Ultra go up to 64GB. Prices range from around $5 for a 16GB card up to $15-20 for a 32-64GB card. Performance is fairly consistent across brands, with average read speeds of 20-30MB/s.
Future Outlook
The usage of Class 4 SD cards is expected to decline as higher speed cards like Class 10 and UHS become more affordable (PCWorld). However, Class 4 cards will likely remain relevant for more basic, standard definition needs where high read/write speeds are not as necessary. With the continued development of newer and faster standards like SD Express using PCIe 4.0, Class 4 cards may eventually be phased out (B&H Photo). But for now, they still serve a purpose for budget-conscious consumers who don’t require cutting edge performance.
