The introduction of the speed grades Class 2, 4, and 6 for high capacity SD memory cards (SDHC) was an important step in showing consumers that there are more differences between products than just capacity. However, the market basically consists of budget/mainstream cards, for which performance is secondary, and of enthusiast products. We looked at 13 of the latter group, and we found more significant performance differences than the speed class ratings would suggest.
Write Performance Makes the Difference
Many of the high speed memory cards we tested reached almost 20 MB/s read throughput. Some cards were probably bottlenecked by our Transcend M5 card reader, but we didn’t find faster card readers to work with. However, read performance isn’t the issue: we found substantial performance differences of up to 100% in the write throughput benchmarks, where the cards delivered between 9 and 18.6 MB/s. And the speed classification didn’t help much, as some Class 4 cards delivered better write performance than some Class 6 products.
Clearly, reviews are necessary to judge whether or not a SDHC memory card is truly fast. The best products in this roundup were the Lexar Professional series and SanDisk’s Ultra III card, but don’t expect them to be inexpensive.