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46

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

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

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 ...


11

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, ...


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

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.


7

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

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 ...


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

Adobe RGB image in a monitor that only displays sRGB? I'm not sure if here lies a misconception. A monitor does not only displays sRGB or Adobe 1998, they display a percentage of them. If a monitor displays 100% sRGB color space it will display a percentage of the other (70%-80% ish. I'm not sure at the moment). I am sure you have seen the typical graph ...


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

The short answer: Because wavelength is a single value, and the entire range of colors we can perceive is not representable by a single value, any more than the dimensions of a rectangular solid can be represented by a single measurement. To continue the analogy - you could quote the solid's volume, but there are many different solids with the same volume....


3

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

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

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.


3

No. CIELAB images are just as subject to different displays as RGB images. As you note CIELAB is converted to RGB in order to be displayed since displays do not use CIELAB. However, if displays are calibrated to the same white point and profiled then they will display images consistently so long as the images are within the display's gamut. And CIELAB is ...


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

It does not seem to be substantially different from standard CMOS sensor other than the fact that most Illunis cameras seem to be based on CCD rather than CMOS chips. The three color bands centered on 450nm, 550nm. and 625nm are certainly similar to most Bayer masked sensors in consumer cameras. What it does seem to be substantially different from is other ...


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 ...


2

The color filter is supposed to mimic our eyes perception of color, it does so imperfectly, but usually well enough. The way we understand color perception is based on opponent process theory. For example you can see that the "red" filter sensitivity is bimodal, this is supposed to mimic the eyes perception of "red" at both very low and high wavelengths. ...


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