5 As fast as the Class 10, & twice the capacity!zen1zen1 | 25/02/2011 | See all zen1zen1's reviews (2)Top 100 Electronics Reviewer BEFORE I START, you should note that this website seems to have the habit of changing the product, but keeping the same thread of comments. Quite why this is done I don't know. Changing the price is one thing, but when the actual product(s) change, it makes all the past comments in the thread invalid. As a result, we can already see where people here have been mislead into buying based on others comments, or based on an out of date item description, & then found they didn't receive what they were expecting. Quite un-acceptable in my book...... Anyway, on to my review ;This review is for the SanDisk Extreme "Video" 8GB 20MB/s Class 6 SDHC memory card. Nothing else was included, except a tiny plastic case which protects the card when it isn't being used.I bought it at the sale price of just GBP15.99 - an excellent deal at the time, compared to prices found elsewhere. I also bought a similar SanDisk Extreme SDHC card for the same sale price, rated at a faster 30MB/s Class 10, but with half the capacity at 4GB.These SanDisk cards regularly receive good reviews for being rugged, reliable, & faster performing (though more expensive) than other brands - so I won't go into that other than to say that I agree. However, I wanted to know how the 2 cards I had just bought compared, & whether the Class 10 was worth the extra money (or smaller capacity, depending on how you look at it!)I used some free speed-test software called CrystalDiskMark, & my newly purchased card reader - the fastest I could find. It is the SanDisk ImageMate All-in-One external USB, also from this website, & claims a max read/write ability of (up to) 34MB/s.My tests on the 20MB/s card produced results in line with what I was expecting, with the main, "sequential test" giving a read speed of 19.0MB/s & a write speed of 17.9MB/s. However, when I tested the 30MB/s card I got very similar results - if anything, very slightly slower! (I also tested some other cards, & fortunately found them all to be slower than these 2.)So from this test, I can conclude that either there is no speed difference between the 20MB/s & the 30MB/s cards, or my card reader had max'ed out at 19.0MB/s.I then speed-tested each card in turn in my camera. I set it up in manual mode, so that all variables remained constant, & then held the shutter-release down so that it took photos at 10fps for 1 minute. For the first few seconds, my camera was able to maintain the full 10fps, as it filled up its internal memory buffer. After that & for the remainder of the minute, the camera had to write directly to the SanDisk memory cards as fast as it could. It managed this in small spurts, as it fired off a few shots, wrote them to the card, & then fired off more shots again, over & over. I repeated this for each of the 2 cards, & compared how many photos each card had managed to capture in the 1 minute period.My test results showed that there was little difference again between the 20MB/s & the (so-called) 30MB/s card. The 30MB/s card managed to capture maybe 4% more, but if the speed rating is to be believed, I would have hoped for 50% more photos captured. Again, it could instead be down to the limitations of my camera's recording speed & not the card's, but combined with my earlier card reader test results, I doubt it.Incidentally, both cards are more than capable of HD video.SO IN CONCLUSION, I have been unable to achieve any real-world speed difference worth speaking of, between this 20MB/s Class 6 card, & the more expensive (half the capacity) 30MB/s Class 10 card.You do the maths & make up your own mind!