I am looking to use an A7r to digitize slides and negatives at high quality. The current state of dedicated slide scanners is dismal - cheap consumer units from the likes of Pacific Image, fantastically expensive Imacons and the old Nikons that were introduced nearly 15 years ago! After talking to a large number of folks who have done this, I am relatively sure that I can build a rig that gets better quality than any of the above except, perhaps, the Imacons.
I am thinking of using an A7r on a Beseler copystand, mounted above a custom light source based on a Sony flash unit behind diffusion. The reason for the Sony flash is that it is a relatively well color balanced light that will automatically compensate for the density of the original (put the flash in TTL mode and let the camera decide). It also has a very wide range of manual power settings. The images will be held on the stage in enlarging carriers, which do a better job of ensuring film flatness than most of what "real" scanners use today.
The A7r makes an appealing camera head for this arrangement because of its combination of high resolution, wide dynamic range (any "real" film scanner except the Imacons has absolutely terrible DR by today's standards - the Nikons were very good in 2003, but pale by comparison to anything vaguely modern), reasonable cost and utility as a camera for my other (landscape) photography. A D810 would share the resolution and DR, but it is MUCH heavier to hike with, and much more expensive. I don't own the A7r yet, and may be open to a D810 instead if I can't figure out how to get the A7r focused close.
The only problem with the A7r is getting the right lens on it for this application. There is no native-mount macro lens, and no clear expectation of when there will be (and will it have a flat enough field to be a copy lens, anyway)? One possibility would be a Canon mount adapter and the 100 mm L macro lens (or the MP-E lens). There are good Canon adapters out there, which should retain precise alignment. Sony's own A-mount adapter opens up only uninspiring lenses (an old Minolta 100 mm macro and a couple of Sigmas and Tamrons with some copy to copy variation). There doesn't seem to be any Nikon adapter that allows native aperture control on G lenses, and the best current macro lenses are all G models.
Besides adapting the mount and using a Canon lens, there seem to be two other possibilities. One is to get enough extension tubes on the camera to make the superb Sony Zeiss 55 mm 1.8 focus to 1:1. Unfortunately, they have to be auto tubes (eliminating the idea of having a machine shop make one), in order to have aperture (and focus?) control, and the only E-mount tubes I can find are 10mm and 16mm lengths, ranging in quality from ebay no-name tubes up to a Kenko set. I would either have to buy two sets and use all four tubes, or buy THREE sets and use all three 16mm tubes, ignoring the 10mm tubes. I'm not sure that many Kenko bayonets in a row will maintain absolutely parallel planes! I'd be dubious about stacking that many pieces even if they were all extremely precise, and the mid-grade tubes only make it worse.
The last possibility is to use a bellows (either an auto bellows and the Sony Zeiss lens or a manual bellows with a dedicated enlarging/copy lens). Bellows units in E-mount seem to be vanishingly rare - the only option seems to be the Novoflex, which can connect to anything with enough adapters, but it is both expensive and I worry about the precision with all the adapters. There is also the new Cambo Actus mini view camera, which is designed for E-mount, and is adjustable enough that it can be made truly parallel. The Actus is very expensive, but also otherwise useful (the Novoflex is somewhat cheaper even with all the pieces, but has no other use).
Of course the less creative option is a D810 with Nikon's excellent 105mm G macro lens. It's slightly cheaper than the A7r with the Cambo and a copy lens, more expensive than any of the other possibilities (about the same price as the A7r with a Novoflex bellows and a copy lens).
-Dan
