“Canon has a built-aperture mount adapter on a patent pending. Because the lens image circle can afford that extra light ghost in it may cause, Canon seems to have addressed by an internal aperture in the adapter. Canon’s next generation camera that sounds like little by little starting to move.

. Patent Publication No. 2011-107255
2011.6.2 Published
2009.11.13 filing date
. Conventional mount converter
Adjust the flange back only
Not consider the difference of the image circle, causing unwanted ghost light
. Canon patent
Aperture converter having an adjusting means
Aperture and manual operation of locks available
And electric drive aperture, the lens can be controlled by information
With a means of communication”
Egami, Google Translation from Japanese.

Canon applied for a patent in Japan for 50mm F2.8, 90mm F2.8 and 35mm F2.8 lens. Via Egami

The patent document and its summarized:
◦ Patent Publication No. 2011-107313
◦ Published 2011.6.2
◦ Filled 2009.11.16
Embodiment 1
◦ Focal distance f=50.20mm
◦ Fno=2.90
◦ Half angle of view 23.32 deg.
◦ Image height 21.64mm
◦ Lens length 84.64mm
◦ Back focus 40.01mm
◦ Macro -0.950x
Embodiment 2
◦ Focal distance f=90.40mm
◦ Fno=2.90
◦ Half angle of view 17.90 deg.
◦ Image height 29.20mm
◦ Lens length 117.18mm
◦ Back focus 65.43mm
◦ Macro -0.480x
Embodiment 3
◦ Focal distance f=35.20mm
◦ Fno=2.90
◦ Half angle of view 31.58 deg.
◦ Image height 21.64mm
◦ Lens length 102.44mm
◦ Back focus 40.10mm
◦ Macro -0.480x

Sigma Normal 50mm f/2.8 EX DG for Canon EOS
Tamron Telephoto SP AF 90mm f/2.8 Di for Canon EOS
Tokina 35mm f/2.8 AT-X M35 Pro DX for Canon EOS