By site editor Dan Chung:
There is growing evidence that several owners’ production models of the Blackmagic Cinema Camera are experiencing serious issues with infinity focus on certain lenses. Initially, users identified the popular EOS fit Tokina 11-16mm f2.8 as a problem lens, with an inability to focus anywhere near infinity when used with the BMCC. Now other users are reporting that other lenses are affected too.
BMCC+Tokina Inf Test from Raitank on Vimeo.
Japanese site Raitank.jp has posted a sample video showing the issue in their BMCC with the Tokina 11-16mm. The reason this lens has attracted particular attention is that it is most widely used fast and wide zoom option for EOS cropped sensors. The other popular zooms in this range do not has the same fast f2.8 maximum aperture.
It seems that most genuine Canon EOS lenses are working as they should because they tend to focus slightly past infinity. The main exception seems to be the recently released 40mm f2.8 STM lens which some users claim gets nowhere near infinity.
Other users are saying that older legacy lenses and even manual focus Zeiss ZE lenses are also affected. On Blackmagic’s own forums user Phillip Mortimer has posted several examples of problems achieving infinity focus with vintage glass and adapters. You can download them here for the first camera he tested, and here for a replacement that was sent to him by Blackmagic. It is clear that both cameras exhibit the issue.
I have run some tests with my own BMCC and several lenses and it appears that I too have the same issue. Lenses that achieve infinity focus on a Canon 6D or C300 do not do so on my BMCC. So far I have tested the Canon 40mm f2.8 STE, Zeiss ZE 18mm and 85mm lenses, along with several Leica R lenses adapted using the excellent Leitax R to EOS adapters. To a greater or lesser extent they fail to achieve infinity with my camera.
I need to run more tests and will do so over the next few days to try to get to the bottom of the problem.
For their part Blackmagic Design have so far claimed that the flange depth of the BMCC “as accurate as possible to the EF flange focal distance of 44mm”. I asked Blackmagic’s Kristian Lam to comment on the issue; he assured me that they are looking into it, adding that it is an ongoing investigation and they have nothing further to add at this point.
There is some speculation online as to the cause of the problem. Whether is it simply incorrect flange depth, poorly calibrated lenses (seemingly a lot of them) or optical issues due to the glass sensor cover remains to be seen. It is also interesting that early testers of the camera did not highlight the issue much (although Cinematographer Frank Glencairn has said his camera has the issue with the Tokina 11-16mm). One possible explanation is that earlier cameras were set up slightly differently prior to the other sensor glass issues being fixed – as we reported here.
As a new BMCC owner I can only hope that there is a swift resolution to this issue. At this point I was hoping to be using and reviewing the camera from a news shooter’s point of view – but that will have to wait until this is sorted out. Of course we will keep you updated on Dslrnewwshooter.com
