Upload & Sell: Off
'Pointless....just use a D800E if you are going to attach giant lenses'
Why compare these two chalk and cheese cameras? They differ enormously in just everything other than that both take photographs! Size/weight/EVF/properly implemented LV/carry ability/lens lineups/alt lens capability/cost/mass market friendliness, and so on. One is an established old regime and part of history, the other a very promising start to a new future way of doing things.
The question also carries this underlying message that everything the a7r can do a D800e can already do so why use the a7r, for large telephoto usage.
First, arithmetic: 1000 grams plus 1000 grams (our generic telephoto, but so many of Nikon's lenses are in this category, such as the decidely non-telephoto 14-24):
2000 grams in a huge package loads a tripod very heavily - you need a larger and heavier head and pod legs and QR system. But leave that aside too.
2000 grams Nikon, 1470 grams a7r. You save 26%.
Attachments: many telephotos and other huge Nikkors lack a collar, but every such lens that goes on an a7r gets a very nice lens mount on its adapter - see Fred's excellent setup in the Canon a7r thread for details - that actually provides more stability since the lens only stresses the adapter lens mount, whereas the Nikon with many alt teles or even its own struggles along with its body tripod mount and QR system carrying the entire 2000 grams.
Still pointless? How about we factor in a great focus assist/peaking system in the a7r? And how many users never use anything other than a tele lens? I don''t know any...so with a more midweight 600 gram lens we have:
1600 grams Nikon, 970 grams A7r. You now save 52%. More examples with smaller lenses still are not needed. It spells versatility...
Whichever way you cut it, the mainstream Nikons are very obese cameras, and they can never ever shed that excess weight. And size. They work very well for a small sliver of the market IMHO - strong armed sports pros, celeb pros (papparazzi), birders in hides maybe, weddings...these all mostly *sanctioned events*. Other usages? Street? Family? Travel? Hiking?
Then we have the new impetus for compact FF telephoto design that just arrived with the a7 series - since most of us are interested in the future as well as the past. I bet Zeiss and others will enveil plans for shiny and wonderful telephoto lenses before most people's next birthdays...CN never cared for small anything in digital - big is beautiful to them - just like 60's US cars with wings, but that does not mean it cannot be done, just look at some m43 optics and extrapolate up.