Luminous Landscape Forum
Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: MatthewCromer on June 18, 2015, 11:30:03 am
-
Reproduced from a reply in the DPR Canon Full-frame forum:
However, the small flange distance on the Sonys creates difficulties for lens designers because it sharpens the angle at which light strikes the sensor, creating loss of edge and corner sharpness and more vignetting from more light fall-off--all because of the small flange distance and the sharp angle of incidence. This puts pressure on Sony's lens designers to raise the exit pupils of their lenses to male the angle of incidence less acute. But this makes Sony's lenses longer and bigger--many on dpreview have noted that the Sony FF lenses often seem longer and bigger than one would like or expect.
This is simply and completely wrong. I've read this meme dozens of times, and it is provably untrue.
Lens designers with the E-mount have the option to move the rear lens element as far away from the sensor as desired. This is indeed how Sony E-mount cameras can mount almost any other type of lens - they simply mount the lens further back away from the sensor via a metal tube (adapter). And that is how Rokinon delivers their E-mount lenses - they take their SLR designs and add an extension tube to the lens body, so they have the correct mount distance on E-mount cameras.
The short flange distance simply adds options to lens designers, it does not take any away. They can place lens elements as close at 18mm from the sensor, or as far away as needed. Any suggestion otherwise is simply incorrect.
-
You're absolutely right, but there's so much nonsense posted every day on many forums that you would have a full-time job trying to de-myth it all.
(http://pegelli.smugmug.com/photos/i-QCnzSZK/0/L/i-QCnzSZK-L.jpg) (http://pegelli.smugmug.com/Other/My-Smug-Mug/n-SzsWG/i-QCnzSZK/A)
-
The same rumors were spread again and again a few years ago about the F mount being too narrow.
You've got to wonder when those Canon fanboys will get a life... ;)
Cheers,
Bernard
-
The E-mount will vignette if the lens's exit pupil is too far from the sensor. The Minolta 200/2.8 loses the extreme corners at all f-stops. I don't *think* it's the LA-E4 adapter at fault, but I don't have an optical bench to prove that.
But it's certainly not the flange distance at fault.
--Matt
-
I took the attached photo last August with an A7r & Nikkor 400/3.5, probably at f/8, via a Novoflex adaptor. I think the vignetting is caused by the lens mount.
-Dave-
-
Ever since I first saw a picture of the A7 without a lens, I thought of the possibility of FF sensors being an after-thought for the E-Mount system. Since the Sony sensors rest very close to the lens mount and it seems to be slightly covered by it, my reasoning has being that the farther away the lens exit pupil is, the more chances of vignetting.
I've been told the Nikon mount opening is even slighltly smaller, but because the sensor or film rests far away from the mount there is more chance for the cone of light to spread without being disturbed before reaching the sensor/film plane.
Eduardo
The E-mount will vignette if the lens's exit pupil is too far from the sensor. The Minolta 200/2.8 loses the extreme corners at all f-stops. I don't *think* it's the LA-E4 adapter at fault, but I don't have an optical bench to prove that.
But it's certainly not the flange distance at fault.
--Matt
-
I agree that the Sony mount might cause vignetting due to a narrow throat, but that is not because of having a short FFD per se.
-
Probably caused by the Novaflex adapter since comparable A-mount lenses on the A7 series don't seem to vignette like that.