>>4245932For photography?
In a well lit room, position the lens close to the wall and look at an image that it projects on the wall. Specifically, check the distance at which the image becomes sharp and focused. You are looking for which side is the "image" and which is for looking towards the "object" (objective). Then you use shit, play dough, double sided tape, custom 3D printed parts, etc. whatever means you have to combine this lens with a focusing helicoid adapted to your mount.
