See my Zeiss DSLR lenses wish list at B&H Photo.
Update 4 September: focus for the two frames is now added/shown/explained.
Two frames at f/11, 2 minutes with Zerene Stacker, and aside from optical limitations in extreme corners of the Zeiss Loxia 35mm f/2 Biogon, this image is razor sharp near to far. Additional time and effort versus single image: negligible (given that a tripod was used).
Why don’t camera makes build in such features for handheld shooting, delivering the N originals plus one finished image, all in raw format too? In this age of unprecedented computing power and sophisticated software image processing, the slothful lack of imagination in the camera industry by the major players is shameful: only a few make some half-hearted efforts: Pentax with SuperRes pixel shift mode, Sigma with its elephantine torture of SuperFine image mode.
Update: the Olympus OMD E-M1 has built-in focus stacking. I have not tried it, but of course the tiny M4/3 the sensor size is least needful of the feature. Also, the stacked result is a JPEG: given the space hit of also saving the 8 RAW files for a stack as the camera does, why does it not output a 16-bit TIF as an option?