Nobody has ever complained about a memory card being too fast and, increasingly, electronic manufacturers are expecting you to have high-speed memory cards that are compatible with certain features. These days smartphones, tablets, and even laptops often rely on memory cards to expand their storage. With consumers demanding higher resolution and less compressed video from cameras, manufacturers have responded by supplying memory cards that are not only more durable but more capable. Today, cameras are recording 4K video to microSD cards and raw HD video to SD cards. Luckily, memory cards have kept up with the rising demand, and the fastest cards around rival SSD drives, though finding out which ones are truly fast can be a challenge.
Determining Card Speed: When memory card manufacturers list their cards’ read and write speeds, they often use terms like “up to” or “maximum” when reporting the spec. A maximum read speed or speed “up to” a certain amount is the maximum burst speed of a card. It might be able to sustain that speed for a few seconds, which is great for saving a picture quickly, such as when shooting Sony’s Alpha a9 or Alpha a9 II at their maximum burst rate of 20 frames per second, but don’t expect to see read and write speeds like that for sustained transfers, such as when you’re shooting video. Plus, some manufacturers are a bit more liberal with the speeds they quote than others. Sustained transfer speeds can vary greatly from card to card, so to determine a memory card's overall speed—just looking at the card's advertised maximum speed isn’t always the best yardstick. It is also important not to confuse bits and bytes. Bits are abbreviated with a lowercase b (as in Mb/s), while bytes are abbreviated with a capital B (MB/s). There are eight bits in one byte. Often, video-recording codecs will list their speeds in bits per second, while cards list their speeds in bytes per second. So, when a video camera like the GH5 records at 400 Mb/s, remember that it is “only” 50 MB/s. Luckily, memory cards have several metrics to help you sort out which ones are fast all around. To the uninitiated, they can be a bit overwhelming and look like random numbers, so in this article, we will not only reveal what the fastest cards are but also help you understand why. UHS (Ultra High Speed) Card Classifications: Some SD cards have UHS (Ultra High Speed) Classifications. A UHS (Ultra High Speed) Classification commutates a card’s bus speed or the maximum speed at which a memory card is capable of transferring data. But, just like plugging a slow hard drive into a 40 Gb/s Thunderbolt 3 port won’t magically speed it up, a UHS classification doesn’t affect the speed of the memory in the card, but manufacturers will rarely make a UHS-I card that is unable to read or write faster than a non-UHS card. Non-UHS SD cards max out at 25 MB/s, but UHS cards can work much faster. Currently, there are two types of UHS classifications: UHS-I Cards, which have a maximum theoretical speed of 104 MB/s, and UHS II cards that allow for a maximum transfer speed of 312 MB/s. UHS-II cards also have a second row of electrical contacts to aid in the speed boost. If your memory card reader or camera does not have the second row of contacts, the speed will be more in line with UHS-I cards. A card’s UHS classification is a good way to help gauge a card’s burst speeds. The Fastest SD Cards: Now that we’ve decoded all the technical jargon, it should be clear that if you want the fastest SD cards you can get, look for UHS-II cards with a V90 rating. Luckily, B&H carries many UHS-II / V90 cards from a few manufacturers. Sony SF-G Tough Series UHS-II Memory Cards are available in 32GB, 64GB, and 128GB capacities, and offer read speeds up to 300 MB/s and write speeds up to 299 MB/s, which should satisfy the most bandwidth-hungry cameras. The Fastest microSD Cards for Cameras- MicroSD cards are essentially miniaturized SD cards, and share the same UHS and speed class properties as their full-sized brethren; so just like full-size SD cards, the fastest microSD cards are UHS-II / V90, which are currently made by Delkin Devices and Lexar. The Fastest microSD Cards for Smartphones and Tablets- Users looking to use microSD cards to increase the storage capacity of their mobile devices could benefit from looking at a slightly different family of memory cards. While cards designed for extremely fast sequential read and write speeds tend to be fast all around, there is little need for a UHS-II bus when you are mostly reading and writing lots of small files, which is why Application Performance Class cards are recommended. The fastest, and only A2-certified microSD card family available right now are SanDisk Extreme cards.
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