In a few short years since the launch of the first 4Mb flash memory card, the number of flash memory cards available for digital cameras and other devices has exploded with a number of different formats and speeds of memory card.
Not only are there different shapes (the format) and sizes such as Secure Digital (SD) Compact Flash, Memory Stick etc, but also different speed ratings.
Memory card speed is the card’s performance with regard to how quickly data can be transferred to or from it. The card speed is often stated in ‘Times’ ratings i.e. 12X, 40X etc (just as the speed of recordable CD’s and DVD’s is measured), and sometimes more specifically in megabytes per second (Mb/s).
By today’s measure, sub 20X represents a standard speed, 20X to 40X is mid-high speed and over 40X is high speed. The chart below shows the relationship between the two figures.
8X = 1.2 Mb/sec
12X = 1.8 Mb/sec
20X = 3.0 Mb/sec
25X = 3.8 Mb/sec
30X = 4.5 Mb/sec
40X = 6.0 Mb/sec
60X = 9.0 Mb/sec
66X = 10.0 Mb/sec
80X = 12.0 Mb/sec
90X = 15.0 Mb/sec
133X = 20.0 Mb/sec
Why do we need different or higher speeds cards?
This in turn takes longer to record onto the memory card. For example if you have ever used a high megapixel camera with a standard speed card you may have noticed the time lag between pressing the shutter button and being able to take the next picture.
This lag or delay, in most cases is caused by a slow write speed, similarly copying your photos to your PC could take time too and is caused by a slow read speed.