WIde angle converter lens (0.5X)

Description:

This lens - made by Sigma - has a 77mm front optic with clip on lens cap, and is about 50mm long. Also has read end cap

It fits on to the front optic of the lens (approx 45mm) and halves the efective focal length, ie a 50mm lens becomes a 25mm lens. A 35mm lens becomes a 17.5mm lens etc.

Was purchased for an ENG video camera (JVC GR707) a long while ago, but may still be useful to someone.

The pictures:
1) The lens, velvet pouch and stepping ring
2) Simulated 50mm lens without adaptor
3) Simulated effective 25mm lens with adaptor
4) What happens if prime lens is too wide (vignette where inside of adaptor is photographed. The inner part would actually be a circle, and NOT oval as my photoshop image shows!)