Canon focal reducer - Working vintage lenses?

[Christoffer Glans]

I've read that the Canon focal reducer got some problems with some vintage lenses not working with the glass elements due to the lenses protruding too far at the back-side.

What lenses can we actually use with the Canon focal reducer? Which ones do not work? I have an old Yashica 50mm that should work (when I get my hands on the M42 to Canon EF adapter), but it would be nice to increase the collection of vintage lenses for some unique looks. There are some good bokeh monsters floating around eBay, but it's hard to know if they work or not.

 

[Vance Colvig]

How I determine if a lens is mechanically compatible with a focal reducer without posibility of "glass to glass" contact:

Place reducer facing up on a flat surface
Cut a 1 centimeter square of a "post-it-note" of the sticky side area
Using a wooden tooth pick, place the post-it-note "sticky side up" in the center of the front element of the focal reducer
Focus lens to be tested to close focus
Mount lens on the focal reducer
Focus lens toward infinity
If the lens will focus to infinity, carefully remove the lens from the reducer

If the post-it-note square remains in place on the focal reducer front element, there is no physical contact with rear element of the lens to be evaluated.
Obviously, if you find the square sticking to the rear element of the lens being evaluated, there was mechanical contact and possible damage to glass if focused to infinity without the sticky.

Contax Zeiss 18mm, 21mmV2, 28mm f2 Hollywood, and 35mm 1.4 do not focus to infinity.
Contax Zeiss 50mm 1.4 and 85mm 1.4 do focus to infinity.

 

[michael fetner]

Following. From one source here on Red User I heard that the IronGlass helios 58 doesn't focus to infinity, and that their MIR 37 definitely doesn't focus to infinity. But yesterday on Facebook someone was using those exact lenses and said they arent having problems.. Mine should be arriving in 2 weeks so I will confirm when I get them.