http://www.lensrentals.com/blog/2014/01 ... ess-camera
For a while now I have been saying that eventually all cameras will become mirrorless and DSLRs consigned to the past. One reason is that manufacturers will not give us the choice as it will be cheaper to manufacture a camera with an electronic viewfinder rather than an optical one. Of course, both Canon and Nikon face the issue of migrating from one to the other without losing volume on current DSLR sales and successfully competing against the mirrorless incumbents, but that is a different matter.
To show what I mean, this is the final image from Roger Cicala's A7R disassembly. There are remarkably few components, just a dozen main parts and 29 screws, which must have quite an effect on the manufacturing bottom line.
Compare it to the Nikon D7000 which he had previously stripped down. Even though this picture was taken part way through the teardown, there are already more components shown than for the A7R in total. Putting a D7000 together has to be a far more complex and expensive task than it is for the A7R. There is also the issue of aligning optical components, as illustrated by this quote from the D7000 article: "The AF sensor is very precisely aligned to the mirro (sic) box so once we touch it nothing short of a service center realignment would let this camera focus properly again."
