such a thing as adapter for video-to-spot?

[SGarriott]

I've got a single 110deg wide 3500lum video light and would like to make it two soon. However there are numerous instances when being able to point to something with a high-power, narrow spot would be great, and I'd rather not have to manage more batteries, O-rings etc and then handle 3 lights in addition to camera.

I haven't a whole lot of experience when it comes to lights, but was wondering why I can't find any sort of adapter to change a wide beam into a spot beam - something like a wet-lens for a camera, just for a light. As far as I can tell, it should be physically possible. I've played around with various magnifying glass elements in front of my video light, both on land and underwater - interestingly I saw absolutely NO difference in the beam when underwater. Seems to me some kind of convex lens should be able to considerably narrow a wide beam, but maybe the beam has to start off VERY narrow in order for it to work.

My video light does have a spot function, but it is less powerful and hardly what I would call a true spot. I want something I can use to clearly "point" with, not just a dimmer, narrower flood.

Tips, ideas, experience? Thanks!

[John63]

would a snoot work ?

[Stig]

The problem with using a magnifying lens underwater is the refractive index of water being quite close to that of glass or plastic. If you use a very strong plastic lens you should get some effect - I had a play with a cheap +10 dioptre 'close-up' lens for underwater macro photography and it certainly helped but was probably only +4 dioptre in water.

Snoots are used on strobes for this purpose but it won't be a high-power narrow spot as all the snoot is doing is cutting out the wider parts of the beam. Retra sell a "Light Shaping Device", or LSD, for their strobe which includes some lenses to concentrate the beam and it's highly thought of on the Wetpixel forum but it's pricey.