posh.wiki

If you actually care about speed, that is.

The latest plague on my wallet has been getting into photography (thanks, Az). As a part of that, I've been learning about SD cards, because after trying to write six 24.3MP photos per second in RAW+F onto an UHS-I SDXC with only 10MB/s, I've run into the issue of minimum continuous write speeds.

That said, this post isn't just for photographers. This advice applies to anyone who needs a fast write speed: sports and nature photographers, videographers, drone pilots, and even some gamers.

Yes, size fraud happens too.

I would be remiss to not mention that size fraud is also a problem in the memory card market.

Some counterfeits will have as little as a few megabytes of storage, yet their online store listing and even sometimes their firmware will report gigabytes. It's important to check that the storage size is as-advertised before use by filling the card completely with data and then reading it all back and ensuring its integrity. You can do this using f3 if you're running Linux or macOS, or h2testw if you're on Windows.

That said, this post is about the much harder to spot speed fraud, so let's get into that.

What's the big deal, anyways?

Most consumers will never hit the upper limits of a memory card's speed. Your average smartphone, digital camera, and even handheld games console doesn't need nearly as much speed as top-of-the-line memory cards can provide. But some of us do.

If you're a gamer, you might notice some performance issues.

If you're a photographer, you may notice your continuous shutter mode slowing down after a few shutter releases, costing you brilliant shots while waiting for your camera's buffer to flush.

If you're a videographer, you may find yourself unable to record video at all, cutting your recording sessions short while you offload your existing footage onto external storage.

No matter your use case, if you need high speeds and don't have them, the effects range from minor to major inconveniences.

What to look for in speed

Sometimes you'll see packaging on a memory card advertise "up to" a certain number of megabytes per second. These numbers are misleading, mostly marketing information for the uninformed consumer. They are best-case scenarios achieved in perfect conditions, in a lab or even theoretically.

The number we really need to care about is the continuous minimum write speed, which is conveyed in a symbol. This video does a good job of explaining the historical reasons behind these symbols, but basically you can take any number inside a "C", or after a "V" or "E", or 10 times the number inside a "U", to be the minimum continuous write speed in megabytes per second.

A couple of notes on this front:

• You may find cards that have multiple symbols on them, each suggesting a different speed. There's a bit more than just the speed to these standards, so it is theoretically possible that a card could satisfy for example U1 and V10 but only C6.
• A number inside a "U" is the UHS speed class, which tells you about minimum write performance; this is not to be confused with the physical UHS interface version, which appears as roman numeral I, II, or III, which describe the physical contacts on the card.

So, why should we buy directly from the brand?

Most consumers will never contend with minimum continuous speeds. A significant majority of buyers will get the card, see that it stores data, rate it 5 stars, and move on with their lives. You, then, as someone knowledgeable about memory card speeds, cannot make an informed purchase, and are not unlikely to end up with a card that doesn't meet your needs, potentially tens or hundreds of dollars out if you can't get a refund.

This isn't a small-scale problem. Knock-off memory card sellers run rampant on online marketplaces. YouTube channel FStoppers bought 6 SD cards from Amazon, with all 6 turning out to be fake.

The top result when I search for "sd card 64gb" on amazon.com is a SanDisk card*, but if you click into the listing and scroll down, you will see that it's sold by a third party (not Amazon or Sandisk, but a distributor, who I am choosing not to name as I assume in good faith that their cards are legit and do not want to cause undue tarnish to their reputation, nor do I want to spend 35 dollars to verify their authenticity). In fact, of 9 Sandisk card listings on this page, 2 are sold by Amazon and 7 by third parties.

So, it is my recommendation that you should buy your memory cards directly from the brand. This way, you have a reasonably sound guarantee that you're getting the card you actually paid for, and a guaranteed recourse if you end up with the wrong product.

And before you go review-bombing genuine cards...

It's important to note that the memory card is only part of the equation.

You may see slower read/write speeds depending on what hardware you have. A USB-2 port, for example, will only transfer about 60MB/s at its very best, so you can't use it to test a V90 card. To verify E600 compatibility, you'll need USB 4, Thunderbolt 3, or another port with suitable speed, plus a suitable card reader.

It's also important to note that the device writing to your memory card may have certain limitations. Some older devices fail to comprehend the sheer size of modern cards, and hardware that only has a UHS-I interface cannot use the full bandwidth of UHS-II and III cards.

TL;DR

If you're a power user looking for guaranteed high write speeds on memory cards, you should buy directly from the brand to avoid a high likelihood of receiving a fake card that's convincing to the average consumer.