There are several ways to view stereoscopic or 3D images.
The best and easiest way for most people, 3D images can be viewed using a specialised viewer (stereoscope) such as the one produced by Dr May that inspired this project. The viewer can be used with printed copies of the photos or by placing the viewer against the screen of a phone, tablet or even a laptop or desktop computer.
Left-Right pairs without a stereoscope
These have to be at the correct scale, with their centres no further apart than the distance between your eyes. Hold them fairly close to your face and then relax your eyes as if looking to the horizon beyond the images. The two frames will blend into one in the centre, and with a little practice you can bring that central 3D picture back into focus. All the 3D photos on this website are presented as Left-Right pairs unless stated otherwise.
Right-Left pairs without a stereoscope
To view these, you need to go cross-eyed until the images overlap, then bring the central picture back into focus.
Monochrome anaglyphs with 3D glasses
Monochrome images can be rendered in red and cyan for left and right channels, then viewed using red and cyan 3D glasses which are readily available. I have tried this without much success, but remain open to suggestions. If it can be made to work, it would allow the photos projected onto a screen.