Originally posted by kristoffon Unless you have an unusually sharp mirror lens that produces sharp images when viewed at 100% pixel peeping then putting a TC on top will be useless.
With all due respect to the owners of Vivitar/Opteka/Sakar/Samyang, etc mirror lenses, the 3M is at least in my experience, in a totally different class. I've owned some of the others, and they're worlds apart. The 3M is a mirror lens that doesn't know it's a mirror lens. (Except for the donut bokeh, which I actually don't mind on this lens.) For a mirror lens, it's ridiculously good.
I can get a cheap manual TC for $10, which is all you need for a mirror lens anyway, since it's a fixed aperture. If I do try one, I think I'll try a cheapie & go from there. If it's crap (which I suspect it may be) I'll just flip it on eBay & chalk it up as a lesson learned.
And I really meant no disrespect for the Vivitar/Opteka/Sakar/Samyang mirror lenses. I've seen some good images from those. But at least in my experience, it's just a whole lot easier for me to get good results from the 3M.
Cheers,
Bobbo :-)