Q: Why does my camera say "Lens not attached" or unrecognized ?
A: This is a full manual focus lens, no electric contacts, your camera will not detect the lens when mounted, pls switch camera to M mode to work.
Why I cant press the shutter button when lens mounted ?
Normally switch your camera to M mode will solve this issue, for some cameras, you need to setting "Release W/O Lens " to Enable on camera menu or turn off the shutter lock option in menu.
Why is my picture out of focus?
Pls rotate the focus ring on the front body of the lens until the subject is in focus , and focus with live-view to achieve accurate focus. Recommend use with a tripod and remote to keep image stable