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Let’s figure out how to choose a memory card among the many different options and what all these icons on the card itself mean.
unsplash.comSpeed
There are two speeds that are important for any memory card.
Reading speed means how quickly information can be read from the card. For example, when you transfer files from a card to a computer, your computer “reads” the card. The faster the reading speed, the faster you can transfer photos and videos to your computer.
Low reading speed is when you put files transferred from a card to a laptop, during this time you manage to wash, iron, do all the work, dig a garden, get married, raise grandchildren, then return to the computer, and there is only 50% of the load.
Recording speed means how fast information can be written to the card. If you’re shooting frame-by-frame, the write speed may not matter much. If you often take photos in burst mode, the recording speed is important for comfortable work.
Let’s take SanDisk’s card options as an example, where the Extreme Pro is a higher-end card.
Read speed Write speed
SanDisk Extreme Pro Up to 300MB/s 90MB/s–260MB/s
SanDisk Extreme Pro Up to 170MB/s 30MB/s–90MB/s
SanDisk Extreme Up to 150MB/s 30MB/s–60MB/s
SanDisk Ultra Up to 120MB/s 10MB/s
As you can see, Extreme Pro cards have great read and write speeds. If you’re planning on shooting 4K video and/or taking photos in RAW format, quality, performance and speed are important to you, so Extreme Pro is your best bet. If you’re just getting started with photography, then the speed setting may not make a big difference, so to save money, you might want to opt for Ultra.
It’s important to make sure your device is compatible with your card’s speed. Some cameras require a certain minimum MB/s (megabits per second) to use certain features. Always check the specifications of your camera before purchasing a memory card.
Card type
- SD: These are the first SecureDigital (SD) cards with capacities up to 2 GB. You can also see them under the name SDSC;- SDHC: HC — High Capacity (High Power), a new generation of SD cards, increased capacity up to 32 GB; — SDXC: XC — Extra Capacity (Extra Power) the third version of SD cards, significantly increased memory capacity up to 2 TB or 2048 GB; — SDUC: UC — Ultra Capacity (Ultra Power), the latest generation card, announced in the summer of 2018, has a maximum capacity of 128 TB.
UHS bus
Bus — memory card interface and communication method.
Differences in the pinouts of the UHS‑I and UHS-II interfacesDifferent SD cards have different data transfer rates and this depends on the media type. On the map we can see the Roman numerals I, II or III. The larger the number, the higher the transfer rate in MB/s.
- UHS‑I has a theoretical bus speed of 104 MB/s, but the actual transfer rate can vary from 50 to 95 MB/s, depending on your device and card manufacturer;
- The maximum UHS-II bus speed is 312 MB/s. The actual transfer rate is about 299–300MB/s;
- UHS-III with a maximum bus speed of 624 MB/s. This is the new standard, most authors don’t need it.
There is a difference between memory card bus speed and Speed Class.
Speed class
This specification is rather important for videographers who need to know the minimum continuous write speed for video recording. This is due to the technical details regarding data fragmentation, so all we need to understand is what specification we need.
- Speed Class is the number in capital “C”, which can be 2, 4, 6 or 10. These numbers correspond to the minimum number of MB/s for sequential write speed. Does not require UHS‑I, II or III.
- UHS Speed Class defines the minimum sequential write speed for ultra high speed. This is the number in the letter “U”, which can be either 1 or 3. U1 has a sequential write speed of 10MB/s and U3 has a sequential write speed of 30MB/s. This requires a UHS‑I, II or III data bus. UHS Class 3 is not UHS-III.
- Video Speed Class is a new speed class for higher resolution video recording. This is the number next to the “V” on the respective memory cards. The number next to the V is 6, 10, 30, 60, or 90 and indicates the minimum sequential write speed in MB/s. This requires a UHS bus.
If you are using UHS memory cards in non-UHS devices, it will default to Standard Data Explorer and use Speed Class rather than UHS Speed Class.
Video Speed Class
Indicated by the letter “V” next to the number. The table below shows the range and speed of each class.
If you shoot video at 1080p or lower, V6 or V10 is all you need. If you are shooting in 4K, 8K, VR and/or drone, you will need at least V30 or higher.
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