Modifying dive light for video/photography with lens.

There are a few threads on the video light topic.

There is another thread where a three-emitter light
is modified by removing reflectors and moving the emitters closer to the glass.


Could a single emitter light be modified by replacing the reflector with a defocused lens?


I'm thinking along the lines of for example Dragonsub:http://dragonsub.com/en/models/megalitium-videocompact/


Anyone here that has tried it? How much space is needed and what lenses could do the trick?


Cheers
/O

You may also have to add a diffuser.
I've tried wide angle flood lights(MR16) for photos work under water, but the lamps still have a very hot center spot.
This makes getting an even exposure difficult.

Mike D

I've found that small aspherics give a pretty uniform beam when defocused to around +/-30 degrees. I didn't look much at wider beams, but it might work. Specifically, I've played with XM-L and the ahorton 27mm aspheric and the 27mm fresnel aspheric from jspeybro.

OS74 said:

Could a single emitter light be modified by replacing the reflector with a defocused lens?

I'm thinking along the lines of for example Dragonsub:http://dragonsub.com/en/models/megalitium-videocompact/

Click to expand...

They claim that the bare LED has an opening angle of about 160°. if you look at the datasheet of an XML2, you can see that this would include almost the complete angle in which the LED is emitting. It is true that most of the cameras don't have such a wide view, but on the other hand, the amount of light in these extreme angles is also below 20% of the relative intensity.

you could calculate without too much difficulties where you should place a lens to reduce the 160° angle to about 120°, but even then, you'll have difficulties finding a lens that is large enough and with the right focal length to capture even these 80° angles (measured from optical axis, so half the total angle).
Putting the lens closer to the LED than the focal length of the lens should give you the desired result (reducing the total angle) without focussing the light and should give you a fairly even light distribution over all angles.

You're probably better off using one of the commonly used aspherics, or my fresnel lenses if space is an issue, and play a bit with it to find the desired angle.
you may get some chromatic aberrations on the outside of the beam which you may take into considerations or block the aberrations with a field stop (dark ring on the outside).
This is most likely what they did in that light as well (using the bezel to block the anoying aberrations)

Johan

you could throw in some Leds with out optics , if you want to use flood underwater there are many ways to get that... use an optic with 80 deg, or you can use an optic with a frosted lens... or you could use some of the new cree chips cxa 1507 ... many many ways to make video lights

[/URL]10659101_10203159715413351_8456961477454631792_o by sumthngsupnow, on Flickr[/IMG]

instead of frosted lens could use holographic diffuse film sheet

http://cooledgelighting.com/optics-and-diffuser-sheets with less lumen loss for better transparency , heat loses , and color aberration on light edge