There are special optics called "projection eyepieces", that insert into an eyepiece port and are specifically designed to serve as low magnification transfer lenses. In some sense one "ideal" solution is to find a projection eyepiece that has the right correction to match your objectives, plus the right magnification to match your sensor size. But that combination can be tricky and/or expensive to find. If you have to use objectives that need correction, then it's usually simpler to pair a normal eyepiece that provides the correction, with another lens that completes the image formation using the afocal technique. Some manufacturers built camera adapters using the latter approach, with the added lens built into the camera adapter.Aenima wrote:I think i read somewhere that leitz photo adapters used eyepiece projection (or maybe afocal), but hadn't considered that a lens might be used/needed in there somewhere.
It was an attempt to use the ocular as a projection lens.
So, depending on what you read, it could have been referring to the special projection eyepieces, or it could have been referring to the afocal method, or it could have been referring to (mis)using an ordinary eyepiece as a projection eyepiece and just accepting some loss in image quality.