visible-light
When I was a boy (I live in the UK) most light bulbs were incandescents and they were labelled with their wattage. The brightest bulb you could get was an 150 W incandescent light bulb.
Today there are many other light bulb technologies—compact fluorescent (CFL), halogen, LED. Bulbs are labelled with both a brightness in lumens and a power in watts.
How bright in lumens is an 150 W incandescent light bulb? You can't buy them easily any more so I can't check the packaging.
I have been suggested to take photos of the glowing bulb then use photoshop to analyse the colour. Is that a possible solution?
No. The power spectrum of a light bulb is a continuous function $f(\lambda)$ where $\lambda$ is a particular wavelength of light and $f(\lambda)$ is the intensity of the light at just that one wavelength.
A camera throws most of that information away, and reduces a color to just three numbers. That's because your eyes have just three different "color receptors," and almost every color that you are able to distinguish can be mimicked by combining different levels of a red, a green, and a blue light source. The camera, therefore, records the level of light coming through a red filter, a green filter, and a blue filter at every pixel position.
Instead of directly photographing your different light bulbs, you could try photographing them through an inexpensive spectroscope
Supplementary answer to the OP's clarifying comment:
The main point that still needs clarification, in my opinion, is whether we are really dealing with thermal radiation here, i.e., whether the role of electric current is only to heat the material (since the current flow itself is not a thermal state
Good question, and...
Yes, we are really dealing with thermal radiation here!
The heating produced by the flow of conduction electrons in the bulk of the filament is not related to the thermal radiation coming from the few tens of atoms near the metal surface that are producing the photons that we see.
We know this because we can do some experiments:
Now, this does not mean that electron collisions in metals can't make visible light, but the chances that a conduction electron can get 2 or 3 eV of kinetic energy before hitting another electron and that that also happens within tens of angstroms of the surface so that the light gets out is extremely small.
Basically the tungsten does two totally separate jobs at the same time:
update: @Ruslan's comment links to two excellent videos!
Incandescent light bulb turning on at 1000 fps - High-Speed Entertainment shows some low amplitude pulsations of the brightness of the light. I don't know how much they've slowed it down for display though.
Incandescent light burning out at 1000 fps - High Speed Entertainment shows a filament burning in air and then breaking, and we can see the decay of the light emitted from each piece as it cools down.
Then it breaks, no current flows, and the light continues but starts to dim:
When it touches another part of the bulb, that part cools more quickly by conduction than by radiation, so it turns dark. But the bit at the right can't cool easily along the filament because it's thermal conductivity is low along the wire, so it's still glowing fairly brightly:
Best Answer
Here is a comparison chart. The number don't correlate exactly since there are differences in the manufacturing of the bulbs.
