Reducing flange distance?

Started 3 months ago | Discussions thread
ProfHankD
ProfHankD Veteran Member • Posts: 7,590
This is what "glass adapters" do; relay lenses

mapachebasura wrote:

Yeah, I realize I was pretty bleary eyed posting this and completely failed to say that I have a 7D right now (though I am toying with the idea of getting a cheapy mirrorless just for this sort of thing).

Basically, the way you do this is to use a rear-mounted teleconverter to reproject a portion of the view father back. Typical "glass adapters" tend to be about 1.2X crop -- in other words, they're 1.2X rear-mounted teleconverters. Most common for Canon EF/EF-S bodies are adapting Canon FL/FD/FDn or Minolta SR/MC/MD and allowing infinity focus. Those are usually around $30.  Unfortunately, they don't increase rear focus distance by enough to get infinity using a C-mount lens, and I've never seen one extreme enough to do that.

Until just now, I had not tried using an ordinary teleconverter as a rear-focus extender. It does work, sort-of. It would require remounting the teleconverter glass, etc., so it's not very practical, but maybe somebody will play with this sometime...?  As a lead-in to what we'd really like to do optically, take a look at "relay lens" references such as wikipedia or Edmund optics . It's really much easier to simply get a camera that lets the lens get closer to the sensor....

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