Samyang has announced that, as promised in October, five of its full frame lenses are now available in Sony E-mount, and are therefore the first third-party optics with native mounts for the Sony A7 and A7R. The lenses are the 14mm F2.8, 24mm F1.4, 24mm F3.5 tilt-and-shift, 35mm F1.4, and 85mm F1.4. All feature manual focus and aperture operation, and will likely appear under Rokinon, Bower and Pro Optic branding in due course.

The E-mount models are essentially the same as the company's generally well-respected SLR lenses, but with a ca. 26mm long empty tube added at the back to compensate for the difference in flange distance from the lens mount to the sensor. (The E-mount has a flange distance of 18mm, compared to ~44-46mm for SLR systems.) This means that the E-mount lenses are considerably more bulky than their SLR counterparts, and heavier too. If you use both an SLR system and E-mount cameras, it almost certainly makes more sense to buy the lenses in the appropriate mount for your SLR (or SLT), and use a high quality E-mount adapter.  

If, however, you're only going to be using the lenses on an E-mount camera, then in principle the native E-mount lenses should give better alignment between the optical units and the sensors - even the very best adapters won't hold lenses absolutely perfectly straight. And if any camera's going to show up small misalignments, it's the A7R. In this case it would make sense to buy the E-mount versions (at least if you're confident you won't want to use the lenses on another camera system in the future).  

From Samyang's website:

Samyang Full-Frame Lenses with Sony E mount

Samyang has introduced lenses with Sony E-mount to increase its selection of 35mm full-frame lenses compatible with the newest Sony Alpha 7 and 7R cameras.

Following the announcement issued on October, Samyang released five full-frame lenses fitted with the bayonet Sony E-mount, including:

  • Samyang 14mm f/2.8 ED AS IF UMC
  • Samyang 24mm f/1.4 ED AS IF UMC
  • Samyang T-S 24mm f/3.5 ED AS UMC
  • Samyang 35mm f/1.4 AS UMC
  • Samyang 85mm f/1.4 AS IF UMC

Wider selection of lenses currently available with this mount will enable users of Sony Alpha and Sony NEX cameras to take advantage of the best quality optics without any additional adapters. The lenses have been prepared for 35mm format, which makes them a perfect tool not only for Sony Alpha 7 and 7R cameras fitted with full-frame sensor but also for models with APS-C sensor, including Sony NEX-7.

Samyang 14mm f/2.8 ED AS IF UMC (E-mount version)  Samyang 85mm f/1.4 AS IF UMC (E-mount version) 
Samyang T-S 24mm f/3.5 ED AS UMC (E-mount version)