I bought my first BM camera 1 month ago and bought a Sigma 8-16 mm lens at the same time.
During my first tests I noticed when I racked the Sigma lens all the way to infinity then viewed what I shot (later on a large screen) that anything at a distance was way out of focus.
After that I started setting infinity at the little line that that, when followed, takes a right 90 degree turn, then a left 90 turn and ends up at the infinity marking - the distance is about a centimeter. After I started to do that I got sharper images. I also noticed when I put the Sigma lens on my Canon 60D and auto focus to infinity - it again sets the lens to the end of that line (again, about a centimeter from the infinity symbol/racked to infinity end)
Later on I was using the focus helper on the Blackmagic Camera when I was inside and focusing no more than 8 feet away. I found that when the BMC told me the lens was in focus; the focus indicator was showing me I was focused was past (closer to the infinity symbol) where I had been focusing to infinity outside.
I thought maybe there was something wrong with the lens so I replaced it for another one. Same issues.
When I use the lens on my Canon 60D using AF, I have no problems. But when I use it on my BMC I really am not sure where to set the focus when shooting at distances past where the BMC focuser is useful. I do realize that this lens has a very deep depth of field. But when I set to focus manually to 'short of' where I think infinity is, the BMC focuser does not agree with it.
Does anyone else know what I'm talking about and has a way of setting focus on this lens?
I should add I have a Rokinon 14mm, Tamron 17-50mm and Canon 50mm and don't have any issues focusing those lenses.
Thanks!