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Lecture 11: Radiometry & Photometry (20)
rheask8246

It's really cool to see how the spectrum of light changes with different kinds of light! I've done photometry labs here at Berkeley and measured how the spectrum of daylight shifts according to time (mainly due to the how far photons form the Sun have to travel trough the atmosphere as the Sun's position changes). We can see that the daylight spectrum more resembles a blackbody curve since the Sun is approximately a blackbody. Conversely, the emission lines from fluorescent light have peak features indicative of its color.

ShaamerKumar

I agree, I think its really cool to see the different concentrations of wavelengths for different types of light.

lwg0320

I heard that incandescent light is good for health. Does the advantage of incandescent light have something to do with its the smooth SPD curve?

CardiacMangoes

Do the distributions of energy by wavelength for different light types add linearly? I was thinking if you have a cool white LED very close to a halogen lamp, this could mimic the distribution of daylight and thus have an artificial light that would be more "pleasing" to the eye.

Spectato54

The difference between cool white LED and warm white LED is most fascinating for me since the cool white LED obviously has a higher intensity in a "cooler" or shorter spectrum and the warm white LED is more "warmer" or longer on the spectrum. It's just very neat when the math adds up.

jacklishufan

The lecture speed through this part and metioned that different wavelength distribution leads to different perceived colors. However it should also be noted that even if two light rays have different distribution of wave lengths, it is not necessarily true that the perceived color are different. This is because humans only have three different color receptors in our retina and our visual system does not have the capacity to distinguish all wavelengths distribution.

LuxuFate

Why is the SPD of Fluorescent light much more varied/spiked compared to the smooth curves of the other lights?

alvin-xu-5745

How do the spikes in fluorescent and cool white LED contribute to how they are perceived? Do the spikes in the different areas (green/orange for fluorescent, blue for cool white LED) change our perception to emphasize certain colors, or is there no noticeable difference and the spikes symbolize something else?

joeyzhao123

An interesting connection with these graphs has to do with blue light I feel. The cool white led's definitely feel harsher at night when you want warmer colors.

ShrihanSolo

If anyone is curious, the spectral power distribution for stars including the sun is modeled by Planck's law, which roughly creates the top left diagram we see. The distribution shifts to lower wavelengths with higher temperatures - so blue stars (and flames) are hotter!

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