It has now been confirmed by Sony that a7 full frame mirrorless cameras have an inherent flaw. As sonyalpharumors.com reports, initially some reports from a7 users started to come in. They suggested it’s a flaw indeed, as there’s little place for mistake in the tests performed. Here’s one of the messages sent by user Joe (quoted from sonyalpharumors.com):
Sad to say that I can confirm that the a7R does exhibit light leak around the lens mount. This was reported on Sony’s Community site. To test it, put the body cap on, use either ISO25,6000 or ISO16,000 and take a 20-30″ exposure. Shine a flashlight/phone LED light around the lens mount. The image will show the leak at the 9 o’ clock position.
Here’s a direct link to the post at sonyalpharumors – you’ll also find a link to Joe’s evidence there. The rumor page also reported that online gear stores removed the info stating a7 is weather sealed from the product description. The discussion is also ongoing at Sony's community page here.
Now Sony acknowledged the issue in a statement:
Sony is aware of and acknowledges this light leak problem with the A7 and A7r and our engineering department is currently researching a solution. We will release a notice to the owners once a resolution is found.
Sonyalpharumors also links to Ferrell McCollough’s blog, where you’ll find a DIY temporary remedy to the issue (Ferrell's photo below).
Additionally, if you’re interested in the a7, sonyalpharumours.com posted a light-hearted comparison of Sony’s a7 and Canon’s 5D Mk III cameras. It was originally recorded and uploaded to Youtube by DigitalRevTV, and though it’s not serious for the most part, apart from burning a 5D Mk III with a blow torch, it does make a few accurate remarks – here’s a direct link to the video.