Brian Mills
November 12th, 2015, 10:35 AM
Hello All:
Recently I posted about how off I found the witness marks on my Rokinon lenses to be, and the consensus I found was that I shouldn't be too worried about it and shouldn't expect them to be 100% accurate.
But after failing to achieve infinity focus with another lens, I started to worry if my backfocus is off on my camera.
So I took out the Sony 28-135, put up a Siemens star at 8', zoomed in all the way and focused. When I went all the way wide and hit magnification, it was off quite a bit. So I focused wide and then zoomed in. Same thing, by the time I got to the other end of the zoom, focus needed a pretty significant adjustment.
Do the rest of you that have the 28-135 find that it is parfocal?
I don't know how I can test to see if the lens is not parfocal as advertised, or if it is backfocus on camera.
Any thoughts? Thank you.
Recently I posted about how off I found the witness marks on my Rokinon lenses to be, and the consensus I found was that I shouldn't be too worried about it and shouldn't expect them to be 100% accurate.
But after failing to achieve infinity focus with another lens, I started to worry if my backfocus is off on my camera.
So I took out the Sony 28-135, put up a Siemens star at 8', zoomed in all the way and focused. When I went all the way wide and hit magnification, it was off quite a bit. So I focused wide and then zoomed in. Same thing, by the time I got to the other end of the zoom, focus needed a pretty significant adjustment.
Do the rest of you that have the 28-135 find that it is parfocal?
I don't know how I can test to see if the lens is not parfocal as advertised, or if it is backfocus on camera.
Any thoughts? Thank you.