Loreo Lens-in-a-Cap

This is an attachment that actually replaces your lens to enable you to take 3D photos.

Mine is about 2 years old, so these comments may no longer apply, but in terms of quality, it's pretty poor! It produces different color casts on each side, so you have to correct that before you can get a good image.

3D photos ideally need a broad depth of field, so it only has f/11 & f/22 as options for aperture, which means you really struggle in low light, and it also has a very narrow field of view.

It's available for at least Canon & Nikon, but you need different versions for full-frame and clipped sensors.

On the Nikon, all camera sensors are disabled, so you can only shoot in full manual mode, so it's a matter of trial and error to get it right - I tend to use the flash in manual mode and use that to set the exposure.

Oh, and by the way, it's a lot of fun!