Thought this may be of interest on the lighting side…

I was looking on Darkplaces and noticed that a group are planning on using a light meter to do comparisons of lights, measure each one and get figures being the thought behind it, as well as photographing them.

The problem of using a light meter, which measures Lux or Foot Candle’s is that you are actually measuring the amount of light and power that falls onto the sensor and they should only be used for areas with wide (almost diffused) light sources such as the inside of buildings, outside daylight, light levels in a photography studio etc… they should not be used for the measurement of light from a sharply focused point such as torches or in this case head lights, unless of course each light source has exactly the same light dispersion profile, with is not going to happen.

To put this into perspective, say you have 2 sources which both output 100lumens of light, but one is 10 deg, the other 20deg, the 20deg will show half the power of the 10deg, which is not true. This can easily be demonstrated, by say powering a 5mm high brightness white light LED up and putting it up against the light meter, it will easily cause full scale deflection on a 20Klux setting, likewise so will a 20W low energy light fitting, but the light fitting will light up a whole room, whilst the LED will not.

The only quantitive way to measure the true total light output from various lights is to use some equipment based around an integrating sphere, where the principle of measurement is to capture all the light emitted. These are a lot more complex and cost many orders of magnitude more than a light meter.

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Would there be any other way of "grabbing" more of the light?

For instance, how about putting the light meter under a semi opaque light globe (lthe type of thing you have in a bathroom sometimes). Have the globe positioned in middle of a chamber with light meter inside base pointing upwards ie not directly towards light source.

Or, how about a large white board (with matt surface not glossy) and point the light meter at the board rather than at the light source? In other words, shine the lights, say in the middle of a chamber, at the board, and have the light meter between light and board, pointing towards board.

At the risk of attracting howls of protest from the light brigade, I have to admit that I'm not hugely bothered about which light is brightest. But then I suspect that most people would agree that we decide on our own individual preferred lamp on a balance of size, weight, light output, features, robustness, reliability, flexibility and instilled bias 😉

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Try a Braun F910... 😉

Like this?

http://cgi.ebay.co.uk/Braun-F910-professional-Flash-gun_W0QQitemZ260192047052QQihZ016QQcategoryZ15221QQssPageNameZWDVWQQrdZ1QQcmdZViewItem 

I agree with Simon, about lighting being your own preference, I just wanted to point out the errors of the intended technique.

However in terms of trying to concoct something half workable, the globe idea could possibly work if expanded. I would say it would be better to put the light under test inside a glode to try and get an even diffusion, tight beams would probably still create hot spots - don't know.

The best test without the proper gear I think would be for everyone to have a go at using each light, and then do pros and cons, spread, beam qual, cost of ownership, blah, blah - it sounds like it could turn into a light spotter convention, if people arn't careful!

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Yes, JnC. that flash gun! Sorry, being obtuse, again ::)
Output 200Watt seconds. 12,500 BCPS. GN 224!
Two of those, couple of flashes each!
Don't all light meters come with diffuser/integration heads? Mine does but probably won't do, what I think, you wish to do.
Have a look at flash light meters; there are surely some out there, contemporaneous with the F910, which will measure such high light levels and not be too expensive.
Don't forget to measure the light temperature.

Hi Y'all,

I reckon the best (and only useful?) way for a potential user to compare/contrast light performance is to see comparative beam shots taken at the same camera settings.

Even better, line up the lights about ten yards apart in a quarry, and take a picture from above, but that's probably not very practical.

http://acidinmylegs.blogspot.com/search?q=beam+shots  - which is about bike lights, but no matter, and the blogger has also set up some interesting gear to record runtime on a laptop.

Cheers,

JM

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Oh, and by the way, the bar has just been raised in the LED headlamp department...

The new Lupine Betty is a 7-emitter 1400 lumen head torch, yours for a mere £632.45 (discounted from £695...).

So I'm sure all you light junkies will just be queuing up to buy one...

JM

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Just stumbled across this thread whilst time wasting in the random 50 thread page. JohnnyM was extoling the virtues of the Betty... it now appears to be up to 1,500 lumens. That's a WiseLED Tactical 1500 - helmet mounted 😮

http://www.lupine.de/2009/en/products/lightheads/betty/ 

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