![]() You can imagine that I might get a more detailed spectrum graph if I just added up the numbers from all 120 rows of pixels in the image. You can see that the blue lines have more blue than the other colors, that the red lines have more red than the other colors, and that the yellow line near pixel 160 is the brightest and is actually saturated (note the flat top and the artifact where the blue "shoulders" are dimmer than the background). I've taken a row of pixels near the middle of the image (row 60, actually, marked by the arrows) and plotted their red, green, and blue components on a graph. ![]() To show you how straightfoward it really is, here's the example spectrum from anna v's answer. If you only care about those numbers along one dimension, you can make a plot of them instead of a two-dimensional image. If your light meter is a digitized CCD readout, however, it probably has an intensity measure for free that has been calibrated at the factory: each pixel on the CCD reports one 1 number, where 0 means "no light struck this pixel" and some maximum number 2 which means "this pixel received more light than it was able to record"). The "proper" way might be to measure the emitted power in watts into a particular wavelength bin, but that takes a lot of careful algebra and calibration to get right. However there are a lot of different ways to measure intensity. It is what it claims to be: intensity of light at that wavelength.
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