This is something that I've tried to find an answer to for a long time with no results so maybe the combined intelligence of the FW community can come up with an answer.
What is theta compensation in respect of camera lenses?
Here's what I know...
Some Contax camera service manuals mention lens theta compensation. Apparently, some Zeiss/Contax lenses have it and some don't. To indicate to the camera whether the lens has it or not, the switch that tells the camera if it has a AE or MM lens attached has an extra position that differentiates between lenses with or without theta compensation. There's nothing in the manuals that indicate what difference it makes to the camera and manually moving the switch through the positions appears to make no difference to the camera. Of the lenses I recently bought, the 50mm f/1.7 and the 18mm f/4 has compensation, the others (25mm, 85mm and 135mm) don't.
So anyone know, or would like to guess, what theta compensation is.