Why Strobe when you can have LIGHT!

I have been seeing powerful video lights like the bonica 1500 lumen LED light. Wouldn´t this be better for photography underwater?

I would really appreciatte all input

To quote from this article I wrote:

Try a torch and problems are soon very apparent. The main issue is power, which might sound surprising, especially if you have ever caught your eyes in a beam, just before a night dive. Many dive torches are powerful, but they deploy their power in the wrong way for photography. It is like comparing the engines of a lorry and a motorbike: one is good for lugging a heavy load up a hill the other zipping a lightweight two-wheeler around at speed. Both are specialised for their jobs. The same is true of strobes and torches.

 

Strobes produce a flash of light in an instant of time, lasting less than 1/1000th of a second. Torches shine continuously, and over the course of about a second, a powerful torch probably produces about the same amount of light as a flash. However, this is useless for pictures because a photo with a 1 second exposure will be blurred. Torches also have relatively narrow, focused beams, which makes it difficult to illuminate large subjects. And their beams area not designed to produce even illumination, most have a brighter central spot, frustrating when we want pleasing exposures. Finally, many torches do not produce true white light giving subjects a yellowy-orange hue.

Although note that the picture in the article was taken with a strobe.

Alex

thanks for the input.

if we consider video lights where the hot spot problem is basicly solved with the used difuse light and if we consider the bonica 1500 lumens with a light temperature of around 6000K,

this would mean that it could be used, but...

what are the "other" problems that may arrise?

Video lights just simply aren't enough light (usually). The shutter is only open for a 1/30 of a second at most, and often a LOT less than that. As the quote above mentions, it feels like a lot of light to your eyes, but your eyes aren't blinking open for 1/100th of a second... your camera is.

The final issue is the effect on the critters... if you got a set of lights that was perfectly even, and output as much light as a strobe (but continuously), you'd seriously fry the eyeballs of any critters you were trying to photograph!

I've used my 21w HID canister light (1500 lumens) as a light source on occasion in a pinch, and you end up with dark, moody photos... some were quite nice, but it wasn't the same as a strobe photo by any means. It can work, but it's far from ideal. Strobes just work too darned well at their intended purpose.

To add a bit of perspective, from what I've read, lumen ratings on led lights tend to be significantly overstated, perhaps by 50%. Your 1,500 lumen may be only 1,000. I really don't know.

A 100w 120v incandescent light bulb is rated at 1,750 lumen. The water column also take a significant bite. Why not try doing land photos with your camera, with only light source being 60w bulb with diffused covering? What kind of exposures might you need, and at what distances?

B&H Photo sell for under $400, and for macro, the dimmer could be quite helpful. Light set is 6500K.

I've seen other forum discussion, but nothing definitive regarding results. Seems like everyone wants someone else to try it first.

When I made TV commercials I never found that 8k HMIs were bright enough to produce the quality for stills I could get from Cecil Strobe.

I have been seeing powerful video lights like the bonica 1500 lumen LED light. Wouldn´t this be better for photography underwater?

 

I would really appreciatte all input

Here's a back-of-envelope calculation that may give you some insight.

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Suppose you get a perfect macro exposure with the following settings:

f/32, 1/150 s, ISO 200, full dump with Ikelite DS160

The strobe delivers 160 watt-seconds of light energy into a 90-degree beam in a small fraction of the shutter duration. If you replace the strobe with a video light having the same beam angle and colour temperature, what must be its output power to give the same perfect exposure? The sensor needs to see a total of 160 watt-seconds of light energy during the 1/150 s that the shutter is open. Since energy is "power" times "time",

required power = (required energy)/time = 160/(1/150) = 24,000 watts.

The Bonica 1500 delivers 12 watts in a 60-degree beam (see spec sheet). Even if you account for its narrower beam, which increases beam intensity by a factor of 3, it would still have to be about 700 times more powerful to give proper exposure. Of course, you could increase the ISO to 6400, decrease the shutter speed to 1/60 s, and increase the size of the aperture to f/11, but those are things that we DON'T want to do.

You need a strobe.

Les Wilk

ReefNet Inc.