Forum: Author Hangout

Is there some way lenses can be utilised in a camera to completely block light? How about two orthogonal(?) polarising lenses? Or perhaps a combination of tinted lenses or filters?

As SB notes, this would negate the purpose of a camera.

The only reason I could think of for doing this would be to blackout a security camera for nefarious purposes. For this, black spray paint to the lens would be quicker, easier, and cheaper.

I'll mention that you could definitely make special "lenses" that would do this without seeming to be anything special.

The easy way would be with coatings of the type that are used on modern eyeglasses. Although the wearer can see out perfectly normally, the exterior of these lenses often fluoresces, especially in photos. For example, if you have a glare reduction coating on your glasses and take a selfie with a mobile device outside, the lens will reflect more than you would expect. I've even seen photos where it looks like the glasses are glowing blue, cyberpunk style.

You'd have to hand wave it a bit, but you could say that someone got an applicable pair of glasses, popped out the lenses, and fitted them into camera lens apparatus backwards. I doubt it would really work, but with a bit of setup it would workable.

I actually jury-rigged a light-blocking lens for taking pictures of the recent total solar eclipse, using a pair of polarized sunglasses lenses that I'd popped out and trimmed down to round, and mounted with the polarizations perpendicular on a section cut from a paper towel tube (so it would stand out from the front of the camera body and not interfere with the autofocue). If I'd had more time, I would have set it up so I could rotate one of lenses and have the opacity adjustable, but I only came up with the idea fifteen minutes before the start of the eclipse, after my first effort at making an eclipse filter using dark-tinted film didn't work. (It was both too blurry and not opaque enough.)

It kind of worked, and I think the problems were more down to the cheap camera I was using than my jury-rigged lens. Its autofocus doesn't like taking pictures of light sources, and it doesn't have a manual focus. (I have never gotten a decent picture of a Christmas tree out of it...)

Both infrared and UV photos are relatively easy to take by blocking visible light with off-the shelf filters:
https://kolarivision.com/getting-started-uv-photography/

Once you go past violet light, you get UV, then x-rays, then gamma rays.

If you go below red, you get IR, then microwaves, then radio waves.

All part of the electromagnetic spectrum.

Film, of course, is only sensitive to some of those frequencies (near infrared to gamma rays, I think), and thermal imaging cameras pick up far infrared. Below that, the "sensors" that pick up those frequencies are leftover fried chicken, and radio/tv receivers.

But I'm guessing that for the purposes of a story, you're wanting to let something other than electromagnetic radiation thru the filter? Something heretofore unknown?

In that case, by using variable strength lenses in each color, you could make some more visible than others (like red, which typically has the shortest wavelength). It's an intriguing concept, and I'm interested in how it plays out.