What to know about SD Cards


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John Ruiz

Shopping for an SD card? The market is full of options, so how do you choose and what to know before you buy? Find out:The SD card format is more than two decades old and hasn’t necessarily replaced all of the older storage formats, but it is a technology worth celebrating. To put things into perspective, the very first 3.5-inch 1 TB hard drive was announced back in 2007. 12 years later, a 1 TB microSD card hit the market and today, these tiny storage behemoths are more affordable than ever before! With so many gadgets still possessing SD card slots, adding or expanding storage is generally a breeze considering how easy it is to find stores selling them at reasonable prices. However, as cheap as they are, I recommend you walk and not run when making that buying decision because SD cards have various attributes and picking the ones that matter most for your use cases is key to getting the perfect SD card without overspending.

This will be your ultimate guide to buying an SD card and I will walk you through the decision-making process.

How do I know which SD card to buy?

The first thing you should do is think about what you will primarily use this SD card for. Will you insert in a device and leave it there or will you use it with a variety of devices? Identify this device or group of devices and analyze the specifications of each. Do these devices all have microSD card slots? Maybe one of them has a full-size SD card slot? Perhaps the only device you’ll use this SD card with is a point-and-shoot camera with a full-size slot? Let’s break this down by SD card types first.

What’s the difference between microSD, SD and others?

microSD cards are basically smaller versions of SD cards which allow more compact devices such as smartphones, tiny action cameras, and IP cameras to feature removable or expandable storage. The stunning fact about this format is the how manufacturers managed to squeeze in a full terabyte in a microSD card. With no full-size 2 TB SD cards currently existing at the time of writing and microSD cards occasionally having a lower cost per gigabyte price, microSD cards have essentially matched the specs of their bigger brothers, the question is, are full-size SD cards completely useless?

The answer is no; some laptops and larger cameras still have full SD card slots. Some microSD cards do come with full-size SD card adapters allowing you to use microSD cards with devices featuring the larger slots but the larger body of a full-size SD card has two key advantages – durability and speed. Even if you look at both a microSD card and an SD card made by the same brand and boasting similar read and write speeds at the same capacity, an SD card with a larger surface area means that it can dissipate more heat. SD cards do not get hot all the time but if your device will be frequently reading or writing large amounts of data on the SD card, the card will heat up and high temperatures will cause performance throttling or physical damage in extreme cases.

Full-size SD cards also have a small slider on the side which you can slide to the padlock icon to force the card into a read-only state. This is useful for safely copying files from the SD card without accidentally deleting anything or introducing malware to the card.

When shopping for microSD or SD cards, be sure you see an SD, SDHC, or SDXC logo on the packaging or card itself. There are other types of small and thin memory cards that may resemble an SD card but are actually proprietary formats. These cards won’t fit in SD card slots and if you believe your device doesn’t have an SD card, check the description carefully to see what devices the memory card works with.

So to summarize, if your devices will exclusively use full-size SD cards, don’t settle for a microSD at all. But if at least one device absolutely needs a microSD card, then you can safely narrow down your selection to that category and just figure out if you will need the adapter or just buy separate SD card for each device.

Working with Adapters

Shopping for an SD card? The market is full of options, so how do you choose and what to know before you buy? Find out:SD card adapters are like big plastic shirts microSD card adapters can put on just so they can fit into regular SD card slots. As long as the card’s capacity and file system fall within the requirements of the device, the device should be able to read it. However, the microSD card suddenly won’t inherit the benefits of a full-size SD card so I wouldn’t recommend using them with cameras and other devices that will frequently access the card. The main purpose of these adapters is for quick copying to and from laptops and external card readers with full-size SD card slots. An adapter could be your saving grace if the device lacks wireless transfer features or has them poorly implemented.

If absolutely none of your devices require a full-size SD card adapter but you want to use the microSD card across numerous devices including ones that lack built-in card readers, consider getting a USB microSD card adapter instead. These adapters may come in both USB-A and USB-C flavors so choose the one that fits your needs. To get the best raw performance out of your SD card, try to avoid using adapters whenever feasible as any form of adapter adds another physical connection layer and potential bottleneck between the card and your device.

SD Card Capacity

Now that you have identified the kind of SD card you want to buy, the next step is to figure out the capacity. Do not skip this step even if you have a big budget because there are some low-capacity SD cards that cost more than higher capacity SD cards with inferior qualities. Figuring out the best SD card memory size will narrow down your list of options significantly. The ideal size to pick depends on what type of files you will store. Doing a bit of math helps a lot here!

For instance, if you plan to record a lot of Full HD or 1080p video, try to record a sample video if you can or check the instruction manual to see approximately how big say a 5-minute video is. A 5 Mbps Full HD video consumes about 20 MB per minute although that can vary if there are more quality options available. Try to calculate a good average of how many videos you want to store and multiply that value by at least two and compute for the capacity. Why two? Because constantly filling up the SD card can affect the performance and may lower its lifespan. SD cards do not have unlimited lifespan and can deteriorate over time depending on how often you’ll use it. On top of that, memory cards with higher capacities tend to have longer lifespan.

There are several cases too where a memory card that has twice as much storage of another belonging to the same class costs less than double its price so you pay a smaller amount per gigabyte for a higher capacity. Finally, your memory needs may expand in the future so having that extra space could really come in handy. Most devices only have a single SD card slot and you can’t just buy an extra SD card and magically merge it with your old one! So do you need a 512 GB microSD card? Go for 1 TB! You might just find a discounted one.

Are there different SD cards for cameras, video, and computers?

So with your preferred SD card type and capacity locked in, it is easy to get excited and search for those specific keywords, buy the most popular SD card, and call it a day. Not so fast! While that best-selling memory card has a good chance of working with your device, you may not be getting the best long-term value if you don’t take the time in determining the type or speed class. If you take a quick look at your search results, you might find a few brands selling cards with the same capacity but are priced all over the place. Don’t panic, don’t think about the brand just yet, and acquaint yourself with the common SD card types you’ll encounter.

High Endurance SD Cards

Shopping for an SD card? The market is full of options, so how do you choose and what to know before you buy? Find out:High endurance SD and microSD cards are naturally superior over their value-focused counterparts in almost all aspects. The most important aspect lies in its durability and the top brands that make these SD cards put various shades of durability on to their products. On the surface, these SD cards are physically tougher and are usually waterproof, temperature-proof, shockproof, and X-ray proof. Check the product description for specific claims.

Internally, the card can withstand more writes before its performance and reliability declines. SD card manufacturers measure the endurance rating in either TBW (terabytes written) or hours. So for instance, a high endurance microSD card that can record up to 20,000 hours of Full HD video means that you could theoretically use the SD card for 7 years straight if device using it constantly records video 8 hours a day. These ratings, of course, are estimates and it’s close to impossible to find reviewers testing these claims but for regular use cases, it is very likely high endurance SD cards will go way past the shelf life especially compared to ordinary SD cards. Looking at the warranty period is a good way to get a reasonable estimate.

Because high endurance SD cards primarily focus on data writes, these types of cards are best used for IP cameras and action cameras where video data is constantly written and you don’t want a single frame skipped. If you just use a smartphone, tablet, game console, or laptop, read on!

Application SD Cards

Application SD cards are sort of the opposite of high endurance SD cards in the sense that read speeds are more of the focus. Lifespan is not emphasized here so you don’t get any detailed spec sheet of how many writes the card can handle. That’s because you’ll mainly write to the SD card whenever you install an app or game with minor writes occurring for storing personal data and settings.

Application SD cards are an option for those who need more than what the internal memory of a smartphone, laptop, tablet, or game console provides. Windows 10 and 11 both offer an option to install or move apps directly to the SD card while Android lets you treat the card as internal storage where it can store more apps and app data even after your device’s internal memory fills up. SD cards will never match the performance of onboard storage but application SD cards are the next best thing and should be your top option if you want optimal performance when launching apps stored there. This doesn’t apply to just apps alone but other types of files you’ll open frequently such as eBooks and movies.

The SD Association currently offers two “Application Performance Class” levels – A1 and A2 with A2 being the faster level. You can tell if the SD card focuses on app performance by looking for the A1 or A2 logos. Ideally, if your budget allows, you are going to want an A2 class SD card because it boasts nearly triple the read performance and quadruple the write performance of an A1 class. Yes, application SD cards have certain standards for write performance too because certain apps and games may also write data to the card if you wish to keep the internal memory free. However, these types of cards are by no means substitutes for high endurance SD cards so don’t use them for video cameras even if they will technically work.

Video Speed SD Cards

Video speed SD cards are strictly for professional photographers and videographers because these types of users frequently record high quality video where large amounts of data need to be written every second. Although the SD Association specifically uses the word “video,” these high write speeds can also benefit photographers who are into burst photography where lots of high-resolution shots need to be taken in quick succession.

Video speed class levels start at V6 and go all the way up to V90 with V10, V30, and V60 filling in the middle gaps. The number used in these class levels represents how many megabytes can be written to the SD card per second. If that sounds too technical, you will need at least a V60 card for recording 8K resolution video or a V10 card if you work with a mixture of 4K or HD video. For 720p video, you can either settle for a V6 speed class card or just work with an ordinary video card. If your device has some special features such as the ability to record 360-degree video or supports multiple video streams, I recommend you try to shoot for the highest video speed class your budget can handle. If you are still unsure, consult the user manual of your device for recommended SD card requirements.

General-purpose SD Cards

If the SD card does not have any fancy packaging and lacks any of the common keywords such as “video,” “application,” “gaming,” or “high-endurance” on its product description, the SD card is likely just an ordinary memory card for casual use. You can use these types of cards in any device that falls within the capacity requirements and you might even get decent performance depending on the brand you pick. Just treat the SD card as a piece of hardware without insurance. Manufacturers normally offer the shortest warranty periods for these types of cards with higher capacities offering a few more years. These types of SD cards cost far less though making them useful for backups or just for adding more memory to devices you may not use on a daily basis. Avoid putting highly important data in these SD cards unless you plan on making copies elsewhere.

Regular SD cards also have levels indicated by the number on the label and packaging. I won’t dive into the details here because in 2022, just go for an SD card with a number “3” housed in a U (referred to as U3) as that represents a maximum write speed of 30 MB/s. If that speed class is too expensive for your preferred capacity, the lowest you should go is a U1 class which offers a fairly acceptable 10 MB/s write speed. Both of these classes fall under the SDXC (Secure Digital Extended Card) category and should work with devices advertised to work with SDXC cards. The only reason you might want to settle for slower or lower capacity SD and SDHC cards (Class 2, 4 or 6) is for compatibility with really old devices.

Finally, some low-cost SD cards may have both application performance class and video speed class logos on the card which may lead you to believe that they excel in both areas. While that could be true, if the price closely matches other budget SD cards, it is likely the manufacturer compromised on the build quality putting it in the jack-of-all-trades camp.

Does brand matter?

Now that you know exactly what SD card to get you will face the final fork in the road – the brand and yes, it does matter! Predictably, there is no perfect way to go about this but at least in the SD card space, there are some tips you can follow which can give you a really good chance you’ll get the best SD card your money can buy.

Don’t spend too much time comparing SD card specs because numbers such as read and write speeds represent maximum values. Depending on the data you are working with, these speeds can vary and remember, heat can negatively affect performance especially if the SD card has poor build quality. Because it can be difficult to see past the brand’s marketing, your best bet is to check the customer reviews.

Filtering the reviews of the SD card to just the negative reviews can give you a good metric as to how reliable the SD card is and possibly how well the brand’s after-sales support is. You want to see the reviews that received a lot of upvotes and comments to find out if this is just an isolated issue or if it is something more widespread. These types of issues are normally rare for respectable brands like SanDisk and Samsung but might be common for their lowest-tier SD cards. Again, this is why I recommend you avoid budget SD cards regardless of brand and at least go for special purpose one like a high endurance model.

You should also check when those negative reviews were written and compare them with more recent reviews. If the vast majority of recent reviewers share positive remarks including the ones that are at least a year old, the risk of buying an SD card from this particular brand is far less. If you are still unsure, feel free to search around for video reviews too especially if speed metrics matter to you as reviewers often test if the performance levels match what is advertised.

Watch Out for Fakes!

Brand matters so much to the point that some rogue manufacturers would make fake SD cards with logos and packaging closely matching the original ones to fool brand-focused buyers. When you are buying online, always check the seller and scrutinize any third-party sellers that may be selling high-capacity SD cards for “too-good-to-be-true” prices. Visit the official brand’s website and check their product catalogues as that is where you can learn their retail prices or MSRP so you can compare the prices with the store and see if these are really discounted or just perpetually cheap but fake. If you decide to buy SD cards offline, check the packaging online first.

The Takeaways…

As long as you purchase an SD card coming from a reputable brand, it is generally unlikely you’ll encounter issues if you have low expectations. But if you are hoping to really get your money’s worth, keep this guide at arms reach and you’ll be very happy with whatever SD card you’ll end up with. If you are still deciding between two equally matched cards by different brands, just weigh the reviews and go for the bigger discount or longer warranty.

Think you made a mistake and bought the wrong SD card? Simply buy another one or wait for a sale so you can buy a larger capacity. Your old SD card won’t be useless as you can set it aside it as a backup or put in any other device you might have lying around!

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