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45

The goal of the imaging engineer has always been to capture with the camera a faithful image of the outside world and present that image in such a way that the observer sees true to life picture. This goal has never been achieved. In fact the best images made today are frail. If this goal were to be achieved, you would need sunglasses to comfortably view an ...


35

You said, this is the information that is captured at first by digital cameras. That is not correct. By themselves, sensors on most digital cameras respond to a broad band of frequencies of light, beyond what humans can see into the infrared and ultraviolet spectrum. Because sensors capture such a broad spectrum of light, they are terrible discriminators ...


17

Simple: the color of the sky is comprised of the mix of all three channels. If it were gray, there would be equal amounts of red, green, and blue. It's not, though — there's a lot more blue, a little less green, and very little red. Pretty much like this: Check out how the arrows on the slider are pretty much exactly at the same percentages as the spikes in ...


15

If this image were RAW, the color would still be there. But since it is JPEG, I'm afraid not. The fact that the image is in RGB format does not help, because I'd you look, you will find that in fact for each pixel, each of these values is set to the same thing: (0,0,0), (37,37,37), (221,221,221), or whatever. That is, they're all gray levels, just ...


12

An attempt to answer simply: We cannot practically capture enough information to store a complete breakdown, frequency by frequency, of all the different wavelengths of light present, even just within the visible spectrum. With RGB we can describe the colour of a pixel using just three numbers. If we were to capture the entire frequency spectrum of light, ...


12

The reason cameras and displays work in RGB is because our retinas work that way. Since our eyes encode colors with those components (RGB), it is a very convenient system (although certainly not the only one) to encode not only pure-wavelengths (which form a more or less deterministic combination of retinal response for each chromatic component), but also ...


11

I think there are some misconceptions in prior answers, so here's what I think is true. Reference: Noboru Ohta and Alan R. Robertson, Colorimetry: Fundamentals and Applications (2005). A light source need not have a single frequency. Reflected light, which is most of what we see in the world, need not have a single frequency. Instead it has an energy ...


10

The spectral response of color filters on Bayer masked sensors closely mimics the response of the three different types of cones in the human retina. In fact, our eyes have more "overlap" between red and green than most digital cameras do. The 'response curves' of the three different types of cones in our eyes: A typical response curve of a modern digital ...


8

There are two interacting reasons. Reason (1) is that the eye (usually) receives multiple wavelengths of light from any given point [so to speak]. White light, for instance, is actually [as a rule] a mixture of many diverse wavelengths; there is no "white" wavelength. Similarly, magenta (often called "pink" nowadays (via "hot pink") ) is a mixture of ...


7

Unfortunately, a JPEG is a one-way, destructive process. It may be RGB, but it no longer contains the colors originally present, only those written in the B&W conversion process. If you had the RAW (.CR2) file, however, you could recover the colors. Think of the RAW file as a master, and JPEGs are created from that.


6

Digital cameras and films to do not have "primaries". The spectral sensitives of digital cameras and films dictate their response to various wavelengths of light. These native responses are sometimes encoded relative to a set of encoding primaries such as rec709, adobeRGB, Kodak ProPhoto (aka RIMM/ROMM), or ACES but these encoding primaries have nothing to ...


6

Have a look at this introduction to color perception and reproduction. It also contains a comparison of CIE, RGB and CMYK gamuts at the bottom, where CIE represents what the eye can do and RGB and CMYK what cameras, monitors and printers can do. In your detailed question, you basically ask, if choosing different RGB filters would accurately model human ...


6

There are at least two reasons this happens: There are very few pure (single / narrow frequency band) light sources. That is to say, your red light is not strictly confined to the "red" end of the visible light spectrum. It emits light in the yellow/green region of the spectrum (and probably just a little in the blue, as well). Similarly, your blue light is ...


5

The colors used in a Bayer filter are already centered as closely as possible to the three wavelengths of light to which human eyes are most sensitive. How sensitive each color is relative to the other two is determined by how the raw data from the sensor is processed. Changing the multipliers used for the red-filtered and blue-filtered pixels is normally ...


5

As someone who regularly works in other spaces (most frequently Lab) I'd say not to worry about it. Since your rationale for going to another space is to make changes you're expecting that your RGB output will not be identical to your RGB input. Any noise should be well within acceptable boundaries. HSV is by no means perfect and it could theoretically be ...


4

Well, if there was a magic RGB setting working for all monitors in the world, there would be no need for calibration anymore, now, would there? In order to bring your display to a given temperature, you would usually use a calibration tool like the ColorHug, Spyder, or Colormunki, for example. Those will be able to measure the light emitted by your monitor, ...


4

Short answer: If you don't mind which colors the CMYK channel values represent, simply apply any random CMYK profile you can find and call it a day. Long answer: there is no really color space called "CMYK" with the meaning that ANY value combination for channels C, M, Y and K results in any specific color. Sure, a high value for Y and zero for the other ...


4

You can get white LED lights that like monitors do actually create white from combinations of very narrow bands of R, G and B light - we perceive it as white of a certain "Kelvin" balance, but if you use a spectrometer, you will see spikes. http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap20/chap20.htm The same goes for fluorescent ...


4

tl;dr: It is way much easier to detect light on three broad parts of the spectra than analyse the frequency accurately. Also, the simpler detector means it can be smaller. And third reason: the RGB colourspace is mimicking the principles of opperation of human eye. As Max Planck proved every hot body emitts radiation with various frequencies. He sugested ...


3

You aren't going to get it exactly right with a single pixel, though you can certainly get that pixel right and then adjust everything else to be visually pleasing (which is usually close enough). To get the color more correct, assuming the light is a continuous spectrum (e.g. sunlight or incandescent bulb) you could get pretty close with a known-white ...


3

Look at a copy of the chromaticity diagram. Notice that along either the X or Y axis there are no colors. XYZ represents imaginary colors, not real colors. It is impossible to make a XYZ sensor. The origin of the XYZ space comes from the standard observer experiments. In combining the red, green and blue test colors to make the colors of the spectrum there ...


3

Currently XYZ filters are produced using thin film technology. It is not very cheap, and not very suitable for multi-megapixel sensors. It also results in somewhat spiky spectral response curves, especially problematic when the light source has spiky spectrum, like fluorescent tubes and some flashes. Yet another reason would be higher noise levels, as XYZ ...


3

No. "White" light contains all wavelengths of light - the Kelvin temperature just affects the proportions of each wavelength. Three lasers will have just three specific wavelengths so can't possibly reproduce the full spectrum of light that is in white light.


3

Why do color channels from a digital camera respond slightly to lights of other colors? Because the filters placed in front of the silicon on a Bayer masked filter all allow some of all the wavelengths of visible light to pass through. They just allow more of the light at wavelengths near the color of each filter to pass. Back in the days of B&W film ...


3

I presume RGB is in that order simply because it is the common spectral order — RoyGBiv, in other words. You will sometimes see BRG or otherwise when a particular computer image format happens to store the channel data in that order. CMYK, on the other hand, is that way because that's the order the inks are normally applied in process color. See for ...


3

Perhaps it’s as simple as the positions occupied by the colors on the spectrum.


2

More generally, what is the nature of the gamut? Primaries as peak sensitivity don't behave the same as primaries for mixing output. I suppose this is necessary to know for RAW importing and would be explicitly stated in a DNG file. Do they vary greatly between cameras? The output from the sensor is RGB based, so if interpreted simply as three ...


2

I found this page which includes the illustration: It reminds me of how the human eye works, which I'm sure is not a coincidence. The similarity is that the difference in red and green spans most of it, with blue breaking the tie by picking out the left side. The green right slope comes down around 630 and blue picks out the half left of the green peak. ...


2

The basic answer is that you can only modify with curves (do not use levels) If and only if you do have the primary color component on the mix, and you can only shift the colors to some degree. You can not in this case: Here is an example image with some clear colors. I separated the channels and you can see for example that I only have information on the ...


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