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Please note: our M42 adapter ring could not be suitable for Pentax Takumar Super Takumar Carl Zeiss M42 series(aperture pin does not fully depress, small tabs sticking out), as ours depresses the aperture pin all the way down
If your camera indicated "lens is not properly installed", please modify the camera menu settings. Usually called the "release the shutter the lens is not installed", you can modify the settings to allow. Specifically refer to the camera manual.Following are some examples: