Memory Card Speed and Digital Camera Speed

By Rob Sheppard

I am finding there still is some confusion as to camera speeds and memory card speeds.

So first, let's look at digital camera speeds. All cameras that shoot RAW and JPEG will shoot both formats in all drive speeds, but because of the file size differences - whether you shoot RAW, JPEG or both at the same time - will affect how the camera handles multiple shots. As the camera shoots at high or low drive speeds, the camera will often shoot faster than the files can be put onto the memory card. The files are then put into a buffer (memory in the camera just for this purpose) to wait in line to get on the memory card. When that buffer is filled, the camera will stop shooting until room is made for the shots.

With RAW, the buffer fills quickly because the image files are large, which means that after a certain number of shots, the buffer will be filled and there is no more room for additional image files, so the camera will quit shooting. With JPEG, the buffer fills more slowly because the files are much smaller, and often the memory card can keep up with the JPEG files so the camera does not quit shooting. This is a big reason for the L or low speed setting on many cameras — since shots are taken slower, the buffer fills more slowly, even with RAW, so you can keep shooting longer than with H or high speed.

Memory card speed affects how fast the camera can pull images out of the buffer and load them onto the card. A faster card will allow the buffer to be emptied faster as long as, and this is an important qualification, the camera has been designed to handle the speed of the card. If a card is faster than the capabilities of the camera, that speed is wasted as the camera cannot go that fast. Using a high-speed memory card with a camera that cannot work that fast will have no effect on camera speed and will give no better results than a lower speed memory card.

Most mid-level to high-end cameras typically could handle the speeds of cards available at the time the camera first came to the market. But then this capability will change over time as card speeds increase during the life of the camera model.

Memory card speed has no effect on how fast the camera can shoot — that is purely a function of the mechanics and electronics of the camera. It can only affect how fast the buffer is cleared, which will affect how long the camera can shoot before it has to stop and allow the buffer to open up.

Note: Rob Sheppard is an instructor at BetterPhoto.com, and teaches many excellent online photo workhops, including Guaranteed Better Photography, The Magic of F-stops: Choosing the Right Aperture, and Storytelling Nature Photos. In addition, BetterPhoto's photography school offers online DSLR camera courses on specific Nikon, Canon and Olympus digital SLR cameras.

Comments

[Paul]

Great information - I understood the limitations for writing data to the card is becoming more of a function within the camera's write speed, rather than the upgradeable card speeds. But where can one find the actual write speed charactoristics for their own camera? I for example have a 40D, but have not found the write speed specification. Understanding this limitation would seem to help define if the super fast / super expensive memory cards are not being utilized to their ability, and one could have saved money by matching memory speed with camera capabilities.

[Kerry Drager]

Hi Paul,
Thanks for the feedback! Here's the response from Rob:

Unfortunately, this is not an easy question to answer. There are no international and accepted standards for memory card speeds and camera write speeds. In addition, no camera manufacturers publish this information. Card speeds seem to be used more as marketing hype than real helpful information. However, camera manufacturers and card manufacturers do communicate with each other. Typically at any given time in development of cards and cameras, there will be some things we can know:

1. New high-end, so-called pro cameras will be able to use the highest speed cards available at that time at those speeds, and likely the next card speeds in the near future.
2. New mid-line cameras will likely be able to take advantage of the higher, and sometimes highest, speed cards available at that time.
3. Low-priced cameras usually cannot use the speeds of even the higher speed cards available at the time they come out, but then they rarely need to as they do not take pictures that fast so users are unlikely to use them for long spurts of photos.

Since camera manufacturers cannot anticipate the future of card speeds, they don't necessarily create technology to handle card speeds of the future until the cards are actually available. Most photographers do not need the highest speed cards unless they are shooting sports where they shoot long bursts of shots continuously, although it is true that high-speed cards can download faster to a computer (though not so much faster that they would necessarily be worth the cost).

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