Choosing a video light for underwater video

[SlvrDragon50]

Yeaa... 13" arms I could live with, but 33" arms are a little ridic haha. I think 1' to the subject is a little too close.

 

[Kharon]

Wish you had posted a couple of weeks earlier. I got back from 2 weeks on Bonaire and my Tachyon gave me essentially B&W pictures and video. Decided to retire my PrinctonTec Shockwave II and bought a FantaSea 1500 lumen 110 degree beam. It looks like I should have spent half as much for a 700 lumen 75 degree beam.

 

[TONY CHANEY]

No the filter goes on once you are in the water so that there are no bubble in between. The design of the SRP dome was more intended to make it look cool but ended up being unpractical as you can't put other accessories on and it has now been abandoned. It is a bit of an issue for companies like SRP trying to make something that at same time is feature rich and looks cool a bit like the tray that also has a design that is counter productive if you use light as requires even longer arms. The light you mention (and is not possible to talk about the quality of the beam without testing it) should work well up to 40" from the lens and would require arms 21" long with a tray one foot wide to operate properly. You can see that you need very soon wide arm as the angle goes past 60-70 degrees

Well at least I got it right pertaining to the filter. Now, if you don't mind, a few more questions. 1) You may have covered this but what is the formula for distance of light from lens based on degree of of the beam? 2) I am shooting video in caves...any suggestions? 3) In order to get max distance without backscatter do I want the lights back of the lens, beside it or forward of the lens? 4) I was using two 21w HID lights with plastic (homemade diffusers and was getting pretty good video). I changed one to a video reflector. Should I have extended the arm for the light with the reflector? Thanks again for a great thread.

 

[Interceptor121]

Well at least I got it right pertaining to the filter. Now, if you don't mind, a few more questions. 1) You may have covered this but what is the formula for distance of light from lens based on degree of of the beam? 2) I am shooting video in caves...any suggestions? 3) In order to get max distance without backscatter do I want the lights back of the lens, beside it or forward of the lens? 4) I was using two 21w HID lights with plastic (homemade diffusers and was getting pretty good video). I changed one to a video reflector. Should I have extended the arm for the light with the reflector? Thanks again for a great thread.

1. You first need to calculate the candela from lumens Iv=Φv2π(1−cos½α)/ then Calculate the Lux Ev=Iv/D2 where D is your distance. It is a bit complicated but there are online calculators
2. I have never done cave diving or not so far. It really depends on your camera viewing angle more than anything. Say that your camera has 90 degrees field of view at 1 meter it means you can cover 2 meters horizontally. So if you want to capture 2 meters than your distance is 1 meter if you want to capture a smaller area then you get closer.
3. Once you have determined your shooting distance based on the angle of coverage of the camera you then can work out your lights needed distance depending on your beam angle of coverage. Moving the camera behind the lights is not a good idea as you are shooting further and further away. In theory moving the camera in front of the lights could work however it depends again on how much surface you can cover take also into account that if the camera and the lights are not on the same line you need ever longer arms. One of the flaws of the SRP tray for example is that it pushes the GoPro that has a focus distance of one foot forward in front of the lights. If you think of the tray as a triangle with 60 degrees angle and you have light that cover more than 60 degrees you now cast the camera shadow on the subject. So you need to move the lights forward to avoid that. Which in turns means longer arms. In short having a straight tray with the lights on the same plane of the camera makes everything much simpler. Take into account that the area where the two beams do not meet is still lit at an angle so backscatter should be limited though you will have shadows.
4. I do not recommend having two different lights as one will cast shadow on the other. For wide angle always have exactly the same model and spec light

 

[SlvrDragon50]

So another question. Could you not just point the lights more outwards vs straight ahead to move the closest minimum distance further away?

Archon's wide angle is pretty hard to beat bang for buck.

 

[Interceptor121]

So another question. Could you not just point the lights more outwards vs straight ahead to move the closest minimum distance further away?

Archon's wide angle is pretty hard to beat bang for buck.

Doing that you are effectively reducing the angle of coverage and using less of less of the lumens which will make the illumination really weak if you had to point it out say 60 degrees you would effectively halve the luminosity in the middle.

Typically lights are also weaker at the borders already so you end up with a little candlelight

 

[TheTrickster]

Interceptor, what do you think about these?

https://www.aditech-usa.com/en/shop/1892-mangrove-videosystem-vs-12l12.html

You have me puzzling over Angle of Beam now!

 

[Interceptor121]

Interceptor, what do you think about these?

https://www.aditech-usa.com/en/shop/1892-mangrove-videosystem-vs-12l12.html

You have me puzzling over Angle of Beam now!

Those are two 9120 lumens lights (you can't just add them as they don't overlap in use)


Despite the incredible power declared due to the view angle the light drops to 1000 lux after 58"

Take also into account that fish do not like to be fried and those lights are still very bright.

at 60% power (that possibly could be a bit more tolerated by fish) you best coverage is around 43"

Now who says that you can use all this light for macro does not know about fish. Most fish don't have eye lids and at macro range with the lights one foot away you can achieve good results even with 300 lumens over 60 degrees. Plus you don't actually want wide beam as you are shooting long focal distances

Could be good for wrecks or caves with a fisheye lense (>145 degrees fov)

In general terms you can cover decently a 145 degree lens with 115 beam but in video you generally shoot 90 degrees horizontal fov to avoid barrel distortion that really makes the 60-80 degree beams the best choice as far as I am concerned

The ideal light for fisheye use would have around 3000 lumens and 115 field of view as reference values. But again this type of shooting is not usual as nobody likes distortion in video (it is instead accepted as an effect in stills)

 

[TheTrickster]

I'm looking at mainly wreck (outside) video.. the lack of power adjustment is my main certain with these - as yeah they say you can never have enough light - but the on/off aspect of these is a bit off putting..

I think I will stick with my original plan of Keldan 4V Unless you can think of something better...?

 

[Interceptor121]

Keldan Luna 4 V are excellent. What camera have you got?