Creo Darwin wrote:
I use a 1D MkIV loaded with Sandisk Extreme memory cards in both CF and SDHC formats. Most of the year I photograph equestrian events, like show-jumping, where I'll shoot off a burst of between three to five frames as they come over a fence, then there might be a break before I shoot again so the buffer never fills and write speed is never an issue. At this time of year with things like Point-to-Point where a number of riders are coming at you one after the other, I have missed a few shots as either the buffer is full or the card is writing fast enough. I'm wondering where exactly the bottleneck is likely to be occurring, I mean can it be resolved by buying cards with a higher MB/s rating? Are CF cards faster than SDHC cards? Or am I simply taking my camera to the extremes of its capabilities? Existing cards have ratings of 60MB/s (CF) and 45MB/s (SDHC).
My guess is the SD card is the bottleneck. Realize that sometimes the manufacturer does not post the write speed (because it is slower) and only posts the read speed which is almost always faster. Cards are not created equal and you don't always get what you pay for. My experience is that SD cards are slower and their numbers are often inflated even more so than CF cards and it depends on which camera you use or even differences in card readers.. These are some speed comparisons. SD Class for the card is below. then there is times ratings. Many of the CF cards are 400 times where as class 10 is 67 times and the cards I have purchased never have written at the speeds they claim (others may have a different experience.).
16× 2.34 (13×) 32× 4.69 (27×) 48× 7.03 (40×) 100× 14.6 (67×)
But again I would say only use CF and a fast CF card. Look at speeds according to Rob Galbraith as of Jan 12th 2012. He is the only one I know doing these type of tests for your cameras and others.http://www.robgalbraith.com/bins/camera_wb_multi_page.asp?cid=6007-10549