Selecting the Write Speed
Not necessarily. The fastest cards available are so fast few cameras can take advantage of their full capacity, so you end up overpaying for performance you don’t use.
So how do you know which card to buy? It’s tricky, but with a little research you can get the right card without breaking the bank.
Three factors influence the usable speed: one is how fast the camera can process the image and write it as data, second is how fast the card itself can write the data, and the third is the data transfer speed between the card and camera.
Cameras themselves are a bit of a bottleneck because they can’t write very fast. You can usually find the minimum card speed your camera requires in the manual’s specifications, often cited by brand and model. If you are shooting still photos in a compressed format like jpg, then the manufacture’s recommendation should be all you need. For the purpose of taking still photographs, you don’t really need a fast memory card for taking typical amateur photographs; the speed of the card is a non-issue.
But there are exceptions. One increasingly common exception is using your camera to take high-definition movies. Now that video is becoming such a popular camera feature, the speed of the card is going to play an important role. If you are planning on shooting 1080 p video at 30 frames per second, get the fastest card available. You will also want the fastest card available to shoot in RAW formats which capture a lot of data, especially when taking several shots in quick succession, like sports photographers.
But let’s say you want the fastest card your camera can handle, but no faster. This is where it gets tricky. in fact, it’s nearly impossible. Manufacturers don’t openly share the top speed at which their cameras write data. Even if you knew the camera’s top data speed, finding a card that matches this speed would be tough to do because card speed measurements aren’t very precise. Some cards are marked X speed, such as 40x or 600x speed, which denotes how many times faster the card is than the 1.2 megabit per second speed of CDs. You will also see cards marked by a class, such as Class 6, or Class 10. The higher the number the faster the speed, although neither the X speed or Class speed are verified by any independent organization. We have to take the manufacturers at their word. That makes the speed ratings a tad suspect.
In a perfect world, both camera and memory makers would provide data speeds in megabits per second in their product specifications. Then you could hope to match them efficiently.
In the meantime, which is likely to be a long time, most non-pros can buy the minimum speed card a camera manufacturer suggests, at the minimum expense, without suffering any loss in performance.