MOTHER’s Light Bulb Comparison Test

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Light bulb performance comparison chart.
Light bulb performance comparison chart.
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To determine the comparative candlepower of various light bulbs per unit of electricity consumed, we set up a simple experiment in MOTHER's photo lab.
To determine the comparative candlepower of various light bulbs per unit of electricity consumed, we set up a simple experiment in MOTHER's photo lab.

MOTHER’s light bulb comparison test shows you the difference between the performance of various light bulbs on the market. (See the light bulb comparison chart in the image gallery.)

While we were working on MOTHER N0. 90’s article about living on low-voltage electricity (see page 132 of that issue), a couple of staff members became curious about the efficiency claims being made for different sorts of lighting devices. Are fluorescent bulbs two . . . or three . . . or x number of times more efficient than incandescent ones? Do 12-volt lamps really use power more effectively than 120-volt models?

To determine the comparative candlepower of various light bulbs per unit of electricity consumed, we set up a simple experiment in MOTHER’s photo lab. We closed an area off with black paper, thus preventing light reflection, and then measured the brightness of a variety of bulbs, using two highly sensitive photographic light meters. At the same time, with a pair of digital multimeters we monitored the power being consumed by each bulb.

By averaging the readings from the two light meters (which, incidentally, varied by no more than two footcandles) we were able to come up with an accurate assessment of the output of each bulb in the range for which the light meters are sensitive. This reading doesn’t include the full range of visible light, but it does emphasize the wavelengths between those given off by an incandescent bulb and those of sunlight. The measurement also ignores the fact that fluorescent bulbs don’t produce equally at all wavelengths. Fluorescent units have gaps in their outputs–hence, it’s said that they don’t emit a continuous spectrum–which could affect their measured candlepowers. Even so, the following chart should give you a pretty good idea of how much useful light you get for your money from different bulbs.

The first nine columns of the chart are pretty straightforward, but the last one bears a bit of explanation. First, to figure the economy of a particular bulb, it’s necessary to consider how much the unit costs. In addition, the fact that one light bulb is more efficient than another may not mean that it uses less electricity in actual practice.

  • Published on Nov 1, 1985
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