New version (backpack_mount3): I re-designed the part that keeps the carabiner in place on the stripe. This new version uses normal PLA (instead of flexible) and should stay better in place and be more durable.

Secure carabiner mount for a dslr camera. It uses my carabiner design which can sustain my own weight.

The carabiner is fixed to the backpack strap with a flexible plate (printed in flex PLA).

On the camera side, the loop is secured with a camera screw such as this one with a rubber joint inbetween to prevent unscrewing. There is a small bump so that the screw cannot untighten without rotating the part itself.

Creality

Ender 3

No

No

1.5

I printed the carabiner and loop with a paranoid 100% infill in polycarbonate. I didn't want to use PLA as it is less impact-resistant, but other materials such as PETG or nylon could be a good option.

I printed the plate in flexible pla, with stronger infill in the "hooks" which hold the backpack strap in place. This is not perfect and the dimensions could need adjustment with other backpacks.

First, insert a joint (16x24, 2mm thick) in the camera loop part. The 1/4 screw should be inserted in the camera loop next, and hit the bump in the counter-clockwise direction. Of the two possible positions (which differ by half a turn), choose the one which yields the correct loop orientation (backward) when tightening by hand (if no orientation works, then rotate the bump in the design). Then, tighten the screw a bit more. This should ensure that nothing moves, and even if it does, it cannot unscrew unless the loop itself rotates by several turns, which is not possible when the carabiner is in place.