The big drawback is the fact With These Rings thatthey do not have any electric contacts, so your camera will assume there is no lens mounted. THEREFORE the f-number will been set to f00. You can not, I repeat, you can not change this, not even in AV mode.
I found this workaround:
Mount the lens normally
Set the Desired f-number.
Now press the depth of field preview button (shown in the picture). This closes down the aperture to the f-number you have set. So, while depressing the DOF preview button, detach the lens from the camera.
Mount the ring with lenses.
HOWEVER I could not get it working. And You Should Keep the button pressed the whole time you're taking pictures. So that's not convenient either.
Because of the lack of electronic contacts you alsohave to focus manually. But that's part of the fun of being a photographer.
The lack of setting the f-number or autofocus is inherent to thesis rings and you should know this When you buy thesis rings. So no stars will be deducted for thesis disadvantages
