A "Pentax 3d adapter 55mm" is a stereo adapter set for vintage Pentax cameras that uses a 50mm or 55mm lens with a 49mm filter thread to take two side-by-side images on a single 35mm frame.
The adapter works by dividing the lens's field of view, and the resulting images can be viewed in 3D using a special stereo viewer, which is included with the adapter set.
It's a device for film or early digital SLRs that creates 3D effects for still photos.
Compatibility: This is a vintage adapter, primarily designed for older film cameras like the Pentax Spotmatic, but it can be adapted for use with some digital SLRs as well.
Aperture and distance: For best results, it is recommended to use apertures between \(f/5.6\) and \(f/8\) and to be shooting from approximately 1.5 to 4 meters away.
Image characteristics: The resulting images may have some overlap or a fuzzy band in the center where the two images meet, which can be managed by adjusting your aperture. You may also experience some vignetting at the edges of the image.