While the two-digit Canon EOS line has made continuous progress, the Canon EOS 60D felt like it took a down-market turn for a few reasons. It switched from the ostensibly "more pro" Compact Flash format still used in both flagships by Canon and Nikon to increasingly more popular Secure Digital card, used in most lower and mid-market cameras (as well as across the range for other makers, like Olympus and Pentax). The camera saw a reduction in its burst rate from a maximum 6.3 (optional 3.0) fps to a flat 5.3fps, and it lost the increasingly-important AF-microadjustment support as well as an X-sync socket. Canon's line in general has been appearing hindered in recent models through its less-advanced sensor fabrication technology, allowing Sony-based cameras (like most Nikons) to gain leads in pretty much all categories.
While the Canon EOS 70D shows a correction for the former issue, returning elements like an X-sync socket and AF-microadjustments—as well as a faster burst rate—it is not going to correct the latter in one prosumer camera. Despite that, the EOS 70D does contain some engineering improvements, including innovations where Canon still leads: auto-focus capability. The EOS 70D introduces what Canon calls a "Dual Pixel CMOS AF" sensor. Each of the 20.2MP on the Canon sensor actually splits the logical pixel into two physical photodiodes which can be used for phase-detection focus. The increase in effective AF sites can, according to Canon, allow for fast phase-detect autofocus across 80% of the frame, down to F11 and very low light levels and works fully with all current Canon lenses. Most historical lenses also work, but some will only use phase-detect for an initial focus, and contrast detection for fine-tuning focusing. The EOS 70D marks a welcome return to innovation from Canon in its prosumer line which at one point was the harbinger of the market.