Understanding SD Cards

Posted on February 08 2019

Understanding SD Cards

Understanding SD Cards

If you’re anything like us, trying to wrap your head around the plethora of SD cards available on the market and their varying specs and class ratings can be a challenge at the best of times. Lucky for you we have done all the hard work and researched our butts off to bring you the down low and knowledge required to get your Action Camera, Dash Camera or Drone up and running. With that said, hold on to your hats as we take you on a roller coaster ride of the wild world that is the SD Card.

What do the symbols on a Micro SD Card mean? 

Kaiser Baas Action Camera SD card

1. Type 

This is the type of card; different card types use different file formats and newer cards won’t work in older card readers. 

2. Format

This refers to the type of format the card is. The differences between the formats are significant:
microSD: Has a capacity up to 2GB, and works in any microSD slot.
microSDHC: Has a capacity of more than 2GB and up to 32GB, and works in hardware that supports either SDHC and SDXC.
microSDXC: Has a capacity of more than 32GB and up to 2TB (although at the time of writing, 1TB is the largest available card), and is only supported in SDXC-compatible devices.
microSDUC: Supports cards up to 128TB, and will require a compatible device.
In addition to checking that a card’s format is compatible with your hardware, you need to check a few other details, too.

3. UHS Speed Class Rating 

This is the minimum sustained writing speed of the card; important for video recording. UHS Speed class 3 cards will never write slower than 30 MB/s, UHS Speed class 1 cards never slower than 10 MB/s.

4. Speed-Class Rating

This is an older speed-class rating. It is redundant of the UHS speed class, but many card manufacturers include it, as well, since many consumer products still recommend products based on the old standard. A Class 10 is the fastest of the old speed class ratings and a class 10 card is verified to never write slower than 10 MB/s, class 4 would never be slower than 4 MB/s.

5. Capacity  

This is the card's capacity: SD cards range up to 2GB, SDHC cards range from 2GB to 32GB, and SDXCcards range from 32GB to 2TB.

Handy tip:

Here's a good reference showing what you can record on an SD card  based on size.


At 14MP you can take 26000 photos on a 128GB card


At 4K you can take 4:40

At 1080P you can take 9:20

6. Bus Speed Interface

The initial SD bus speed of 12.5MB/s is the Default Mode and was defined by SD1.0. Then a 25MB/s High-Speed Mode was defined by SD1.1 to support digital cameras. As higher performance levels were needed to support new and faster devices, the SD Association introduced faster speed bus interfaces: UHS-I, UHS-II, UHS-III and SD Express. All of these faster interfaces are available for SDHC, SDXC and SDUC memory cards.

 We hope that gives you a good overview of how to decipher SD cards. If you still don't know what's right for you, click here to view our breakdown of what camera requires what SD card!

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