BetterPhoto Q&A
Category: New Answers

continoue light verses regular studo flash

Complexed beginner.

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November 10, 2002

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November 11, 2002

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November 11, 2002

Could I use one of these reliable with a digital camera? If I adjust the white balance to Halogen.

The lamp I mean is this one:-

http://www.kaiser-fototechnik.de/en/infos02c.htm

I am attracted to it for continous light
particularly in a church or other not well lit places.

Surely in those situations trial and error and manual adjustments on the camera (Leica Digilux 1) would produce
good results OR not what does anyone think?

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August 31, 2004

The only true measures of light are Guide Numbers, Lumens and LUX.

A LUMEN is a unit of measurement of light. It measures light much the same way we do a foot/candle (or Lux). Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light! A LUMEN is equal to one foot-candle falling on one square foot of area.

Candlepower is a rating of light output at the source, using English measurements. Foot-candles are a measurement of light at an illuminated object. Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate

You can find the lumens of any continuous bulb usually on the packaging. It takes a lot of lumens to light up a set. Human eyes are much more sensitive to light than cameras and what seems incredibly bright to use is barely significant to most of our photos. Bare minimum portrait lights should start at 10,000 lumens. I would not even try to do a portrait sitting without my main light being at least 20,000 lumens. With unscientific research, I estimated my test with continuous lighting to make a 20,000 lumen light about a 150 watt-second strobe.

So watt seconds can't possibly be a unit of light measurement either, huh? Yup! Exactamundo! Watt Seconds (ws) are a unit of energy, commonly used in advertising for AC-powered studio flash units. It is not, however, a unit of actual light output, so comparing the watt-second ratings of different flash units is not usually useful. This is why you get people like Paul Huff giving actual watt-seconds vs true watt seconds. True watt seconds is a watt second by definition, while actual watt seconds are white lightning's way of saying their flashes are brighter because they use more efficient capacitors and science. I totally believe that Paul is telling the truth that his lights are brighter than other strobes rated at the same ws but there is no such thing as an actual watt second as an absolute measurement of brightness. You can't measure lumens by watts seconds.

What you CAN do with strobes is measure the light with a Guide Number (GN). The GN is used in flash calculations to determine the appropriate aperture required to cover a certain distance or vice-versa. To find the aperture (f stop number) required to take a photo of a subject you divide the flash unit’s guide number by the distance to the subject. To find the maximum distance that can be reasonably illuminated using the current aperture setting you divide the guide number by the f stop number. In each case it’s the distance from the flash to the subject that’s important, not the distance from the camera to the subject. These two distances may be the same with on-camera flash, but not with off-camera flash or when using bounce flash.

f-stop number = GN / distance
distance = GN / f-stop number

Note that you are not getting a reading in lumens, but just a way of figuring exposure.

And even then, you can't accurately judge most hot shoe flashes against each other since there isn't a standard way to measure. So while flash Neekon and flash Meetz have Guide Numbers of 85 and 100, you would think the Meetz flash is more powerful. But if you really read the side of the box, you will see that the Neekon flash did its test at ISO 100 at 75 feet and the Meetz flash did their test at ISO 200 at 10 feet. So obviously the Neekon flash is much more powerful but Meetz skewed the test to get a higher Guide Number.

So, what does this mean when I am deciding on getting continous lighting or buy a flash?

Anyone that tells you that you should only get strobe equipment because you can't take a good photo with continous light is just silly. But you can see that you need a LOT of continous lighting to match the power of a strobe and continous lighting is not cheap.

The quality gear, that is designed to dissapate the heat and focus the light, is going to cost as much, if not more, than the strobes you can get nowadays. But the advantages of continous light are more than WYSIWYG. Continous lighting gives a very soft look you don't get with strobes without a lot of extras. You can also get a lot of great mixed lighting with continous lights.

Whatever you are going to buy, it helps to understand how things work.

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October 07, 2005

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October 08, 2005