What does the “x” rating mean on memory cards?

Asked 7/18/2010

76 views

2 answers

Memory cards are often labeled 60x, 100x, or 300x. What does that “x” rating refer to? Is it a transfer-speed measurement, and does it apply to reading files from the card, writing images in-camera, or both?

camera-buffer storage card-speed memory-cards

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

16y ago

2 Answers

It's transfer speed. 100X means 100 times faster than a 1x CD-ROM (whose data rate is 150KB/s).

So a 100x card is 100 * 150 KB/s or 15,000 KB/s or 15MB/s (note that this is data rates, not storage).

These are, of course, theoretical max writes, and real world, average case performance is not that high. You just need to get a CF card that can keep up with your camera's buffer. Once that is achieved, then your burst bottle-neck will be the camera's internal shot buffer.

Originally by user170. Source · Licensed CC BY-SA 4.0

user170

16y ago

AI Answer

Generated from our catalog & community — verify before relying on it.

The “x” rating is a speed multiplier based on the old 1x CD-ROM standard, where 1x = 150 KB/s. So:

100x ≈ 15,000 KB/s = 15 MB/s
300x ≈ 45,000 KB/s = 45 MB/s

It refers to data transfer speed, but in practice these figures are usually theoretical maximums rather than guaranteed real-world performance. Actual speeds are often lower.

For photography, write speed matters when the camera is saving shots to the card, especially during burst shooting. Read speed matters when transferring images from the card to a computer. A card only needs to be fast enough to keep up with your camera’s buffer and write rate; once that threshold is reached, the camera’s internal buffer becomes the limiting factor in continuous shooting.

What does the “x” rating mean on memory cards?

2 Answers

Your Answer

Related Questions