Example of a SanDisk Card
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Here are the specifications of the card we purchased. We found it was not the right fit - we needed a MicroSD Card.
Brand
SanDisk
Model name
SanDisk Extreme PRO SD UHS-I Card
Flash memory type
SDXC
Memory storage capacity
128 GB
Compatible devices
Computers, Digital Cameras, Home Theatre Devices, Car Navigation Systems
This refers to the read speed of the memory card, which is how fast data can be transferred from the card to a computer or device.
200MB/s (megabytes per second) is a very fast read speed, allowing you to quickly offload large files like high-resolution photos and 4K videos from the card.
QuickFlow Technology is SanDisk's proprietary technology that enables these high read speeds, beyond the standard UHS-I 104MB/s.
However, the actual speeds may vary based on the device you're using and other conditions. 1MB = 1,000,000 bytes.
This refers to the write speed of the memory card, which is how fast data can be recorded or written to the card.
A write speed of 90MB/s is very fast, allowing you to quickly capture high-resolution photos and videos without running into buffer issues.
Again, the actual write speed may vary depending on the device you're using.
With its high read and write speeds, this memory card is well-suited for capturing 4K UHD (Ultra High Definition) video and taking sequential burst mode photos, which involve rapidly capturing multiple images in quick succession.
However, support for 4K video recording may vary depending on the camera or device you're using, as well as other factors like file attributes.
These are speed class ratings defined by the SD Association, which governs SD card standards.
UHS Speed Class 3 (U3) indicates that the card is designed to support 4K UHD video recording with UHS (Ultra High Speed) enabled devices.
Video Speed Class 30 (V30) means the card has a sustained video capture rate of at least 30MB/s, which is required for real-time 4K video recording with UHS-enabled devices.
The read speed of 200MB/s means you can transfer the entire 128GB of data from the card to a computer or device in about 10.7 minutes (128GB / 200MB/s = 640 seconds = 10.7 minutes).
This very fast read speed is extremely useful when you need to offload a large amount of data like photos, videos etc from the card quickly after a photoshoot or video recording session.
The 90MB/s write speed determines how quickly you can continuously write data to the card when capturing photos/videos.
At this speed:
You could write 90MB (approx 30 RAW photos) of data per second
It would take around 24 minutes (128GB / 90MB/s) to completely fill up the 128GB card when capturing continuously
The fast 90MB/s write speed helps prevent bottlenecks/buffer issues when shooting high-resolution burst photos or 4K video which generates a lot of data very quickly.
Without these high speeds, transferring 128GB on a slower card could take over an hour for offloading, and you may encounter buffer issues when shooting continuous bursts or video on a slower write speed card.
The bus interface refers to the type of data connection/interface that the SD card uses to communicate and transfer data between itself and the host device (like a camera, computer, etc.).
The SD card we have purchased uses the UHS Bus Interface:
This is the newer, faster bus interface for SD cards.
It uses a parallel data transfer interface with extra data lines compared to the older bus.
UHS bus supports different speed modes like UHS-I and UHS-II.
UHS-I supports data transfer rates up to 104MB/s.
UHS-II supports even higher transfer rates up to 312MB/s.
The UHS-I bus allows for the fast speeds quoted, by utilising a parallel data transfer path with multiple data lines compared to just one line in the default bus.
However, to actually achieve the full 200MB/s and 90MB/s speeds, you need a UHS-I compatible host device as well as potentially SanDisk's optimized card reader. Otherwise speeds may be lower if using a non-UHS or older device/reader.
For a 128GB SD card when using it as storage for a security camera, the amount of video you can record depends on a few factors:
Video Resolution
Higher resolution videos like 4K (3840 x 2160) will take up much more space per minute of footage compared to lower 1080p or 720p resolutions.
Resolution refers to the number of pixels in each video frame. Higher resolutions like 4K have more pixels per frame compared to lower resolutions like 1080p or 720p. More pixels means more spatial detail and clarity, but also requires more data to encode each frame.
This refers to how much data is encoded for each second of video. Higher bitrates mean better quality but larger file sizes. Typical bitrates can range from 5Mbps to 20Mbps+.
The bitrate refers to the amount of data that is encoded to represent video footage per unit of time.
It is expressed in bits per second (bps or b/s). A higher bitrate means more data is being used to encode each second of video, resulting in higher quality video, but also larger file sizes.
A lower bitrate means less data per second, which reduces quality but allows for smaller file sizes and enables more footage to fit into a given storage capacity.
Common bitrates for video encoding range from around 1 Mbps (megabits per second) for low qualities up to 50 Mbps or higher for broadcast/bluray quality video. Security cameras often use 5-10 Mbps bitrates.
For the same bitrate, a higher resolution will result in larger file sizes because each frame has more pixels that need to be encoded using the allocated bitrate.
For the same resolution, a higher bitrate allows allocating more data to encode finer details, resulting in better quality and larger file sizes.
So resolution and bitrate work together:
For high quality 4K video, you need both a high resolution (3840x2160) and a high bitrate (15-50 Mbps)
For lower quality 720p video, you can use a lower resolution (1280x720) and lower bitrate (2-5 Mbps)
As an example, a 4K video encoded at 25 Mbps will look significantly better than a 1080p video encoded at 5 Mbps, even though 1080p has fewer pixels than 4K.
Higher resolutions require higher bitrates to fully utilize the increased number of pixels and capture high quality video. The bitrate allocates the throughput to encode that high resolution spatial detail over time.
A codec is a software/hardware component that handles compression/decompression of video data. It encodes raw video into compressed formatted data and decodes that data back into video output.
Common video codecs include:
H.264 / AVC - A very widely used codec that compresses well for high quality video
H.265 / HEVC - A newer codec that compresses better than H.264 for the same quality
VP9 - An open-source codec developed by Google
AV1 - A very efficient, royalty-free codec but requires more processing power
The codec determines how efficiently the raw video data can be compressed into a smaller encoded stream while preserving quality. More efficient codecs mean smaller file sizes.
Both the selected bitrate and codec are very important factors that determine the final compressed video quality and file size. Higher bitrates and more efficient codecs produce better quality video streams and larger file sizes for the same source content.
Assuming:
1080p resolution at 30 frames per second
10 Mbps bitrate
H.264 codec
You could theoretically record around 217 hours of video on the 128GB card:
Many security cameras record with lower bitrates like 5Mbps to maximize recording time.
At 5Mbps, you could record around 434 hours of 1080p 30fps video.
Furthermore, cameras often have dynamic bitrate adjustment and other settings to optimise recording duration while maintaining decent quality.
So in ideal real-world usage for a security camera, you could likely record over 2 weeks of continuous 1080p footage on the 128GB card before needing to overwrite/replace storage. Higher resolutions would reduce that time.
