How do universal clip-on iPhone lenses work?

Question

So, recently I see a lot of clip-on Universal iPhone lenses like this (aliexpress link).

I have a CCTV camera at home. It has a lens which looks like this from m12lenses.com. Can I clamp these iPhone lenses onto these M12 lenses? Will they work?

Answer 1

Can I clamp these iPhone lenses onto these M12 lenses? Will they work?

They'll probably work to some degree. I've taken pictures with an iPhone by holding the lens up near the viewfinder of a DSLR, the objective of a microscope, and the eyepiece of a telescope. All worked better than I'd hoped, but it's more like using sunglasses in front of a digital camera as an impromptu filter than like changing lenses on a DSLR. I think the M12 mount is 12mm in diameter and that's plenty large enough to cover the iPhone lens, but you may have to play with the distance a bit. You can buy a M12 lens holder that would let you take advantage of the threaded lenses to easily adjust distance.

Answer 2

Light from a distant subject enters the lens as bundles of parallel rays of light. We can mount devices that intercept and thus modify the image formatting rays before they enter the camera lens. These devices are called supplementary lens systems. As an example, an ordinary wide-angle front door peephole lens array can be mounted before the camera, and this device causes the camera to function as a super wide-angle. Conversely, we can mount a miniature telescope before the camera, and the camera view becomes telephoto.

Such supplemental lens systems are not new to the photo industry. We can also image directly through the eyepiece of telescopes and microscopes. This is called mounting the camera in the “afocal” position. The word afocal means the device does not cause the image forming rays to focus on the digital sensor. Instead these rays are presented as parallel rays and this allows the camera lens to do the deed.

In most cases the afocal view is substandard, meaning there is a better way to accomplish the task. However afocal devices deliver a lot of bang for the money and, if well designed, a reasonable image results.