Trying to reevaluate bulb brightness.

[Juggernaut]

Are Incandescent bulb life "with all else being equal: wattage, gas fill" the easiest way to find out put? I have a 150 watt bulb and have always believed to put out around 4,400 lumens "efficiency of 29x150", well I was searching through Luxluther's destructive bulb testing and found a similar 150 watt bulb. While most of the bulbs in "my" bulbs category are rated at 300-100 hours of life this one has the lowest life of any I've found at only 15 hours, which is extremely low considering even SF lamps and LF lamps are rated between 25-35 hours could I use the idea that this bulb http://i61.photobucket.com/albums/h75/pike444/bulbs/64633.jpg when ran at around 15 hours of life would produce 7,000+ lumens? First hand comparison against a 3,000 lumen Oracle shows it to be on a completely different level, while next to a PH50 it was just about the same with better throw, against a 85 watt barnburner it's noticeably duller, but not by a huge margin:shrug:, could I be close in guessing I have been underestimating my bulbs performance all this time:thinking:?

 

[mdocod]

"All other things being equal" would have to include more constraints for the bulb life specification to be a reliable indicator of possible output.

Efficiency is also a factor of filament shape, surface area, and length (this has to do with design voltage and current, along with other factors, different filament designs are used for different things, for example;many axial filament bulbs have poorer efficiency as the exposed filament surface area is lower. most very low voltage, high current bulbs also suffer from much lower efficiency from filament shape), also the size of the envelope, double envelope? (some have it), fill gas pressure and mixture (just because 2 bulbs say "halogen" on them doesn't mean that their fill gases are the same and at the same pressure).

Also, sometimes the most important factor is how the bulb "specification" is determined and reported.... Consider, that the concept of "bulb life" could be listed based on many different standards. If it's a flashlight bulb that is direct-driven by a battery, then it would make sense for the flashlight manufacture to re-rate bulb life based on the typical bulb life achieved when driven by that battery. (consider that in most configurations, the initial turn-on is very bright, followed by steadily dimming output. With that "dimmer" output at the end of the run probably running the bulb at a drive level that would actually run for hundreds or thousands of hours bulb life, averaged to the ~10hrs or less that most bulbs would last at the drive level they are seeing on fresh cells).

As another example, and in your case, probably the most important point to consider:
Landing lights are likely rated on the conservative end of things (to reduce liability) taking into consideration the rigors of vibration and the jolt of landing a small aircraft. The "15" hour rating on many landing lights is more accurately "15 hours of vibration and assault before failure and very likely no less and probably more but replace me after 15 hours regardless for safety reasons."

Your landing light probably contains a ~100-300 hour bulb that has been de-rated to 15 hours for aircraft use.

Yes, I'm jumping to conclusions that it is a landing light that you have your hands on.

Yes it's probably a very well designed bulb that throws like a monster

-Eric

 

[Juggernaut]

Thanks for the input, "what ever would make you think I was using a landing light?", Yes these bulbs do see constant voltage compared to a "flashlight battery, or a small car battery in my case:naughty:" who's voltage gradually drops "even if very little" over the length of the light being on it still adds up exponentially. I never really thought of that. As for as shock and abuse, from some of the field test on aircraft bulbs that I've seen the number one time that bulbs blow is on landings, and obviously manufactures have to equate this into their ratings. All of these factors add up to a bulb that isn't being driven to what the average life points to for output. The only abuse that this bulb will see is the reduction of cooling that a normal aircraft bulb gets while in flight. I would never have at first thought that any amount of air movement on the glass envelop of such a large bulb could consequently cool the filament inside, but I have seen some life test on 100 watt landing lights and all of them blow a good deal quicker then they were advertised at "example: the standard GE bulb was rated for 100 hours but only survived 37" the author believed it was because they were over heating on their stationary base. Could their be any truth in that:thinking:?

Thanks for all the help:thumbsup:.