Digital SLR cameras generally save their images to one of two different types of memory card: the majority support CompactFlash (CF), while others such as Nikon's D3000 and the Canon Rebel XS write data onto Secure Digital (SD) memory cards. The latter are inexpensive and favorable for their smaller form factor and better physical contact surface instead of fragile pins. Some DSLRs, however, have dual card slots, such as the Canon Digital EOS 1D Mark II N or the Nikon D300s. Last time around, we reviewed number of UDMA-6 high performance CompactFlash cards on the world's fastest DSLR, the Canon EOS 1D Mark IV, and we promised to put some Class-10 SDHCs through the same tests. That day has come, so read on to find out how Class 10 SDHCs stack against UDMA-rated CF on the Mark IV.