The sense and nonsense of fast memory cards

Monday 2 March 2026, 20:10 by Nando Harmsen | 4,237 views | 3 comments

This article was translated from Dutch with the help of AI. Read the original.

You need to put a memory card in your camera to save your photos. The manufacturer determines which type of card it needs and the maximum speed it supports. How much should you take this into account when buying a memory card?

There are many types of memory cards. You have CF, CF Express type A and type B, XQD, SD and micro-SD. There may be a few others, but these are the most common. Although you no longer see ordinary CF in modern cameras.

There are many types of cards. Here you can see XQD and SD.
Apart from the types of cards, there is also the read and write speed. There are differences there too, sometimes quite significant ones. One card is faster than another, and the variations between them can sometimes make things confusing.

For example, there is a UHS-I SD card and a UHS-II SD card. Both look the same and are interchangeable. But the read and write speeds are very different.

These SD cards can also have the designations V30, V60 and V90. These also indicate how much data can be read or written per unit of time. Can you still follow it?

These are all SD cards. But they are different. Pay attention to the stated write speed. It ranges from 95 MB/s to as much as 300 MB/s.

The manufacturer's advice

The camera manufacturer does indicate which cards are best to use. This is usually matched to the maximum data flow that can occur. In many cases, this is for video.

If your camera has one memory card slot, it is simple. But if it has two memory card slots, the read and write speed may differ between the slots. Slot one is then fast, and slot two is slower.

Let me give you an example. The Olympus OM-D E-M1 mark II has one memory card slot for a UHS-II SD card. That is nice and fast for writing the photos you have taken. The second memory card slot, however, is for UHS-I SD, so it can write the data much less quickly.

One card slot is fast, the other is slow. Quite a few cameras have this. It can sometimes be inconvenient.

What does this mean for the photographer?

How much attention should you pay to the read speed? That depends on what kind of photographer you are. Do you simply take photos at your leisure? Then it makes no difference at all what type of card you use.

Even if you occasionally take a series of ten or so photos, a UHS-I SD card is more than enough. You do not need the maximum write speed at all. A faster card will make no difference in that case.

A large card does not automatically mean that it is faster.
Are you an action photographer, and do you want to shoot long bursts with many images per second? Then a fast card such as UHS-II SD does make sense. But the camera's card slot must of course also support UHS-II.

Apart from being UHS-II SD, the card also has a certain write speed. You can only find that in your camera's specifications. This more or less determines whether V30 is enough, or whether you need V60 or even V90.

Write speed is intended for the buffer

When shooting at the maximum frame rate, the speed of the card does not matter in principle. In most cases, you can simply use the fastest shooting mode, regardless of what type of card you have in the camera.

The photos you take are first written to the camera's buffer, not directly to the card. The photos are then written from the buffer to the card. If you have a fast card, the buffer will be emptied much more quickly.

Pay attention to the write speeds. Which one is suitable for your camera?
There is no point in buying fast cards when your camera is only designed for slower cards. If the camera has a memory card slot for UHS-I SD cards, you can put a UHS-II SD card in it. But the write speed will not be any faster.

Does your camera have a fast and a slow memory card slot, like the Olympus in the example above? Then choose the fastest slot for writing your action photos to. It is best not to use the slower slot.

If you use the second card as a backup, the slowest card slot determines how quickly the buffer is emptied. It is like a chain that is only as strong as its weakest link.

A fast card is recommended for shooting many photos per second.
There is a small nuance when it comes to the buffer. Because the buffer is already being emptied while you are shooting, a fast card will always allow you to take more photos in a burst.

From the card to the computer

When you transfer the photos from your memory card to your computer, the card's read speed is important. If you use a card reader, make sure you choose one that supports the speed of the card.

Are you using the camera to transfer your photos to the computer? Then the camera is the determining factor in the transfer speed. The maximum speed can be found in the camera's specifications.

Should you now buy the fastest cards possible?

As mentioned, whether you should choose the fastest cards possible depends on you as the camera user. For video, it is always recommended. For photography, it depends on what kind of photos you take.

The photographer who takes photos one at a time at their leisure does not need a fast card. The photographer who shoots fast bursts, such as action or sports, will need a fast card. As fast as the camera supports.

Finally, make sure you get a good-quality card. Do not go for the cheapest one you can find. Cheap can turn out expensive. It would be a shame if you lost your photos because of this false economy.

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