Old film slr cameras optical precision?

joellapointe1717 · Apr 28, 2024

I'm working on an opensource project about a slr camera. The distance between the film surface and the lens flange is named "flange focal distance". I'm not an optical engineer. So I want to know about optical precision of this "flange focal distance" (machining tolerances). Furthermore, the mirror in these camera is tilted at 45 degrees. This is flipping the optical path towards a ground glass screen. An image is projected on this surface. The precision of the 2 optical paths may be different. Hence, a focused image on the ground glass may not be focused on the film plane.

Is there some technical papers that explains the precision needs for the 2 optical paths?

IRstuff · Apr 28, 2024

It's a tolerance-based; your ability to interchange lenses with their individual focal plane tolerances, manufacturing tolerances of the camera box, repeatability of mechanisms, etc. The end result is a result of how much you want to spend in containing the tolerances and how much image quality you want to maintain; that partly creates the difference between a Nikon and a Pentax/Mamiya, aside from the cost of the name itself.

You need to start with a tolerance budget, based on the desired image quality you wish to retain.

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Old film slr cameras optical precision?

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