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I know there's some FP people out there who have a pretty good understanding of lights and I'm definitely not one of them. My question I know CF bulbs are more intense than Halogens, but I'm trying to fiqure out the intensity difference between a 35watt halogen bulb and a 20watt cf bulb?



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A 20 watt CL will smoke a 35 watt halogen hands down. This is a paper from Berkley on the efficiency of CF fixtures when put up against a halogen fixture. If you scroll down towards the end, the efficiency of the 500w halogen doesn't even break 5%. The CF that is much much much much less powered is way more efficient.

Also, given the potential fire hazard of halogens, i'd pick CF all the way.

Fallout,

The linked document is very nice, but it confuses the hell out of me.

It talks about efficacy (lumens per watt) for floor stand lamps with the target to distribute light in as much of an area as possible (it mentiones that the downside of the halogen is a bright spot rather than broad illumination). Now, for a tank, we actually don't want to distribute the light throughout the room. Wouldn't that mean that this document is not applicable?

I think to remember that the advantage of Halogens is that one can fit way more watts over an equal area than can be achieved with CF. If that is needed in a freshwater tank is another question.

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Table 2 deals with lumen outputs and efficiencies of the lamps, CF versus Halogen.

A 72 watt CF lamp (measured at 64.95w actual) put out 4826 lumens. Now, a 300 watt halogen (272 actual) put out 3684 lumens. The CF lamp, while having a much lower wattage, threw out more lumens than the power guzzling, hot halogen lamp. If that's not more efficient, i don't know what is.

The figures further on in the report give distribution of light for two fixtures, i believe, so they're not really pertinent in this discussion, if i'm reading it correctly. Each fixture will have a different focus of light. Ideally, you want a reflector that will minimize bouceback, or light that travels off the bulb, hits the reflector and strikes the bulb a second time. More advanced reflector design minimizes this, thus increasing FIXTURE efficiency.

However, for all practical purposes, a halogen lamp is less efficient than a CF bulb, and as demonstrated in that report, will also offer a higher intensity. I'm sure that design and part variables play a role, but overall the above is true. After all, a halogen lamp is just a more advanced incandescent, that's why they are so hot. They convert more energy into heat energy than into light energy.

I was just reading this page on thekrib the other day about people's experience with using halogen bulbs over an aquarium.

Two things that go against halogen over an aquarium:
- color temp issue: only around 3000K, so doesn't have the full spectrum that plants need
- heat issue: halogens are essentially much hotter version of incandescent bulbs. So you run the risk of overheating the tank, unless you put it high above the tank (which then means it doesn't spread the light evenly).

-P

Thanks for all the info on the Halogen. I knew they weren't efficient, but they are so easy to come by I wanted to see if I could make do on a small tank.

Interesting articles. Some of these halogen bulbs actually say super daylight so I'm not sure if that's marketing BS or if not all halogens are the same.

One thing I could tell you is I put a 13w 6700k cf bulb on top of my 5g and then compared it to a 25w halogen desk lamp and the 13w blew it away. The 25w looks dimmer and definitely more red.



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