What's brighter a 15v 150 watt EFR bulb or 30v 80 watt ELB?

[slashmaster]

I've been going through super8data seeing a lot of projectors that have 30 volt 80 watt halogen bulbs of some sort. Are they brighter than the 15 volt 150 watt ones?

[richard p. t.]

Wattage is power. Brightness comes down to power (wattage) rather than voltage. So go for more wattage (power) if you want greater brightnes. Bearing in mind of course that halogens are brighter than straigjt tungsten.

[carllooper]

Yes, as Richard indicated, wattage is a measure of a system's power. And in terms of a light bulb a reasonable measure of it's brightness.

But I add the following because I was once upon a time quite confused by the term "power". And still get confused on occasion. And so perhaps the following might be of help to anyone for whom their trouble might mirror mine.

Power is not in the sense one might use such a word to say "power up the spaceship", or "turn on the power" (as if to supply "power") but is rather the output of an electrical system, or "the amount of work" a system does. In the case of a light bulb the amount of work such does is more or less proportional to the amount of light it gives off: so the wattage (power) is another way of expressing or rating the brightness of the light. It doesn't matter what the voltage/current is. Power, in this sense, is not something you supply to a light bulb as such (which is what has confused me), but what the light bulb does. The amount of work it does. The amount of light it gives off.

But not all the power (watts) produced by a light bulb (as one says) is expressed in terms of the light it gives off. Most of it is, because that's the way light bulbs are designed - it is the job they do. But a proportion of the power will be expressed as heat (to a greater or lesser extent). The bulbs get hot and the air around them gets hot. In terms of the amount of "work" they do, they can be considered as working part-time (moonlighting) as heaters, as much as light bulbs. The more heat a light bulb gives off the "less efficient" they can be considered - but efficiency depends entirely on purpose rather than power. If one were using an electric heater as a light source it would be considered less efficient because it gives off more heat than it does light - but as a heater it would be more efficient, ie. more efficient than a light bulb producing the same amount of power. The power of a system is the amount of work it does, but the proportion of that work expressed as light (or as heat) can differ.

However, in general, to the extent that all light bulbs are within a certain range of each other in terms of their efficiency (competing with each other, as they do, to be a light bulb rather than a heater) the wattages between them will tend to be a ball park indicator (if not better) of their relative brightness. And of course, for bulbs of the same type (same efficiency), the wattage then would be a pretty precise expression of their relative brightness.

So of course to the extent that the efficiency might differ somewhat between light bulbs otherwise of the same power (same wattage), they would then be somewhat brighter or less so with respect to another.

The power of a system is mathematically defined in relation to volts and current, so you could use figures for the voltage and current of a given system to calculate the power of the same system. A figure for power means you don't have to go to that trouble.

C

[RCBasher]

The power rating of a light bulb (in Watts) is the power consumed, not the power output. Power only loosely relates to output brightness and only bulbs of similar construction can be compared. An obvious case is so-called energy efficient bulbs which have a given rating, say 9 Watts, with an equivalent rating, say 40 Watts, to a standard incandescent bulb. 9 Watts is the rating for the bulb, it is the power consumed - period!

It is interesting to compare 50W halogen bulbs with mains (240V) rating versus 12V rating. I looked into this for kitchen spot down lighting and found the 12V version to be brighter, in fact a 12V 35W bulb had roughly the same perceived brightness as a 50W mains bulb. Obviously I compared bulbs with the same size and angle reflectors. I wondered why and concluded that the 12V versions would need thicker wire to take the higher current required to reach a certain wattage (Amps=Watts/Volts of course). This would then allow the coil to be run hotter without burn-out which in turn would improve the luminous efficacy.

So it is not possible to accurately answer the OP's question without knowing the technology involved for both bulbs, the 80 Watt is specified as halogen, the 150W one is not specified. If the later is halogen too then without doubt it will be the brightest. Obviously the reflector size and angle will play a big part in determining to what brightness a subject will be lit from any bulb.

Of course it gets more complicated when we start to look at the colour temperature and CRI of lamps....

[RCBasher]

I missed the clue in the post title when making my last post :oops: So both are halogen and would think that other differences (e.g. relatively small voltage difference, different filler gas) are not enough to overcome the nearly 2:1 power input difference.

[granfer]

Of course, this isn't really about which BULB is brighter.... it's about which PROJECTED image from PROJECTORS with these BULBS is brighter.(See first sentence of first post... it refers to projectors using different bulbs)
......... and that's down to the projector's light gathering, utilising and light propagation characteristics.

One stop down on the lens aperture nullifies a "twice the brightness" light source.

(Tried to keep it short as verbosity is not my forte!)

granfer

[slashmaster]

Thanks for the replies everyone! Now I know! Good point Granfer, a lens aperture plays a part too, along with having a slightly wider and taller aperture, along with a shutter thats closed a shorter amount of time too. I've been thinking about filing 1 degree off the 3 blades of my projector. It closes then opens with time to spare so it can be done! Hey RCBasher, hope you don't mind me changing the subject, but I'm guessing you either do RC car stunts or RC car demolition derby's? Got any film of it?