Lectures by Robert Hant, Master of Color Studies, Taiwan
Section VII Additive Colour Reproduction
Each pixel on each electronic screen is SPD (Spectral Power Distribution), SPD like red light has more long-wavelength spectral distribution above 600nm, invented by Lippman in Paris more than 100 years ago A light-sensitive color image photography method, now a color image of a parrot stored in a museum. However, the three-color photoreceptor optic cone system also has a metamerism. It seems that two identical colors have different spectral distributions. In the additive color method, the three primary colors of R red, G green, and B blue are used for imaging, while in the subtractive color method, the three primary colors of C cyan, M magenta, and Y yellow are used for imaging. In the three-color visual nerve cone (cone), we can see the full-color world. If only the P cone senses red light, there are only red and light and dark levels, only the r cone is also only green and the level, if only the B cone (very A small amount) Then only the blue light and the layers appear. The P-cone, r-cone and B-cone each have a mechanism for completing color separation and combining into color images under the distribution of long wave, medium wave and short wave. We can use RGB three-color black and white color separation film, plus red, green, and blue projection methods to form overlapping color additive color images. Professor Hant uses three slide projectors on the spot to add color separation with three color lights The negative film is overlaid and projected on the screen to form an additive color image. This Analog additive color imaging performance may have been done hundreds of times by the old professor, and the author has been doing it in the color separation industry for nearly 50 years. This is the first time I have seen a familiar experiment, but I am afraid it will be difficult to find a slide projector in the future, and no one will do such a performance! In terms of spectral distribution, regardless of the three-color human optic cones P, r, B, or our color separation R (Raydon W25), G (W57), B (W47) three-color filter, it is a wide spectrum of color Performance, but the color spectrum of many LEDs or lasers is a very narrow spectral domain, and there is a big gap between our vision and the wide spectrum of the filter, but it may also form the same color of the same color stimulus value. Heterogeneous phenomenon. In many cases, unwanted signals are not wanted, resulting in some blind spots in many copies. A lot of visually sensed color light is not in the color gamut that can be expressed by the additive color method. How should we present it? To give up? Or compressed into a color gamut that can be rendered in a deformed way? If the color discarded in the range of reproducible triangles is correct, the removed part will lose its level.
The distribution of red light on the screen spectrum
Lippman's earliest color image
Three negatives with RGB color separation
Section 8 Substractive Colour Reproduction
Three filters Y absorb blue light. M absorbs green light and C absorbs red light to produce three filters overlapping all light is absorbed
The color reproduction of color negative film, photo paper, and printed matter is subtractive color method. The color reproduction is based on the use of C, M, and Y color filters or inks. Each primary color absorbs the transmission or reflection of a specific primary light. , C cyan absorbs R red light, M magenta absorbs G green light, Y yellow absorbs B blue light wave, so each color of CMY transmits or reflects the other two specific light waves in white light. If the two primary colors overlap, the two primary colors are common Can transmit or reflect the original light, C + M shows B blue light, C + Y shows green light, M + Y shows red light, if the three colors of C + M + Y overlap, it means all The colored light is absorbed and cannot appear or reflect the three colored lights, which is the basis of the color reproduction of the subtractive color method. How to make a three-color version of the subtractive color method? Use the red filter to get the C cyan version, use the green filter to get the M magenta version, and use the blue filter to get the Y yellow version. C cyan ink pigments or dyes control red light, M magenta ink pigments or dyes control green light, and Y yellow ink pigments or dyes control blue light. After the three color plates are overlapped, a color subtractive printing pattern is formed, but in fact we cannot obtain the dyes and pigments of the three primary colors that control the absorption of the three primary light. The frequency spectrum is distributed like a square line, which is completely absorbed, reflected or transmitted. It is very thorough, but the reflection or transmission of the existing primary color pigments is not very thorough, or the absorption is not very thorough. Similarly, our visual nerve cones for color interpretation are also somewhat overlapping and shifting. The P cones are also sensitive to red light and green light. These deviations also cause many color reproduction displacement phenomena, so photosensitive film manufacturing or photo paper For color reproduction, certain displacements must also be taken into account. Like some main color-sensitive light waves, such as the main light-sensitivity spectrum of red light moving from 625nm to 645nm, the red components of red and purple increase. Reala, like Fujifilm, has an additional blue and green light sensitive layer. Between the second green light sensitive layer and the third red light sensitive layer, this can produce a greater image contrast in the red part. In modern scan color separation, the logarithmic analog signals of film and photos are converted into digital information files, which are initially received as Rs Gs Bs signals, and then converted into RGB for screen display or CMY for photo paper printing. The spectroscopic characteristics of the Dye dye used in the negative film cannot be a straight-line spectrum. The spectroscopic characteristics of the upper and lower square plates are composed of a combination of curves. Therefore, there will be a drop in color reproduction, making color reproduction necessary. Only some repairs will be more faithful to reproduce. In the printing industry, there are adjustments to color corrections in the electronic circuits of manual color correction, color film correction, and electronic scanning color separators. Yellow dyes have unnecessary absorption of green light, magenta dyes have unnecessary absorption of blue and red, and cyan dyes also have unnecessary absorption of blue and green, all of which cause deviations in color reproduction. Use color couples with orange background and color correction in the color negative film to correct the color shift phenomenon of the above dyes to obtain more ideal color reproduction, but this technique can only be used for color negative film to make photo paper Color correction can be obtained at the time, but this technique cannot be used in color positive films (slides), otherwise the color will be slightly orange when viewed directly. The turbidity of color positive film can also be compensated by the Inter Image intermediate image method to compensate for the occurrence of color deviation, so that the turbidity of the blue area can be reduced, and in the prevalence of digital technology, the color is easier to change using electronic digital technology and is still widely used in film shooting Using color negative film, it is still superior in tone and sharpness.
The ninth section of the reproduction of the tone (Densitometry and Tone Reproduction)
Electronic color density receiving and amplification principle
During the reproduction process, the brightness-related changes are the effects of the tone reproduction. When a painter completes a painting, the tone formation of pixels is done manually. The tone of the image by means of photography is automatically formed. The exposure is performed as a function of Log 10, and the density unit is 1/10 Log. Changing the lightness will change the order of the light and dark on the screen. The difference in Log density 1 is 10 times, Log 2 Represents 1/100 and Log 3 represents 1/1000, so the concentration is calculated by the Log value as a change of 10 times the difference of the geometric order. The concentration is divided into different materials for reflection and transmission. There are light concentration measurement methods and astigmatism measurement methods. The reflections are different in narrow and wide angle measurements. If the tone reproduction is 45 ° angle lighting, the reproduction curve is the most ideal, but many negatives only have a 45 ° angle replication area, and others cannot maintain the 45 ° curve, showing a gentle slope rise or parallel appearance. It is better to harden it slightly by 1.15. Brightness not only controls the reproduction of black-and-white images, but color images not only lose tone but also lose color easily when the brightness is insufficient. On the contrary, increasing the brightness and contrast increases the color and contrast of the picture. In human vision, some colors are memory colors or common sense colors, which also dictates many ways of color reproduction. In the graphic table, the arrows represent skin color, sand color, green grass, and blue sky in the clockwise direction. At the bottom of the arrow is The actual color, but at the tip of the arrow is the visual memory color. It can be seen that the memory color is much higher than the actual color saturation. This is also a requirement of human vision. Increasing r gamma value can increase contrast and color? Richness, not only the brightness is improved, but also after the color? Richness is increased, it is also close to most of the memorized colors. In a landscape photo, the air atmosphere is clear In the case, there is less contrast and color loss for distant scenes. If there is a haze in the atmosphere, distant scenes
Nine format grayscale test table
The loss of contrast and color is greater than that of our eyes, so it is better to adjust it to meet the visual needs. A gray color block is viewed under a white background or a black background, and its visual evaluation is quite different. Human visual judgment will be differently evaluated by the background color, and the results of the instrument measurement will not be affected. A gray series has a large contrast feeling on a white background, and it will feel a reduced visual effect on a black background, so under a normal background, we can use an r gamma value that does not increase or decrease 1.0. If the r value is 1.2 for a darker background, the r value is 1.5 for a dark background, so that the comparison will look similar to the visual evaluation. When we watch a movie in a cinema, because the surroundings are all dark backgrounds, the final r value must reach 1.5, which is much higher than the normal 1.0 r value. Halo or fog fog itself does not have any image, has little effect on the color and gradation of the light part, and has a great influence on the dark color and the dark part. This halo or fog fog occurs, and the impact is evaluated more than the r value of the dark background. The sex is greater, the original 2.0 concentration is only 1.0 concentration value or lower, and the dark background still has a concentration value of 1.3. The slide shows a comparison and reproduction of the r value of the subject, and it also shows an unsatisfactory situation in the dark part, especially the recognition rate of the dark part is not good. Therefore, the use of color slides to copy color slides will result in extremely enhanced contrast. Because general slides have the function of increasing the r value of the image, it is necessary to copy the slides using a copy film with lower contrast. Now using electronic scanning color separation, there is a greater chance to adjust the contrast of the plate to make a suitable image.
Overexposure low contrast, underexposure high contrast
Section 10 Television's Television Technology
The black and white main image signal on the upper left, and the color image on the lower right to complete the color image
NTSC color signal, upper left brightness image, lower left plus Q signal, upper right plus I signal, lower right complete image
The CCD photon signal on the left is concentrated by pushing, and the CMOS image signal on the right is concentrated by electronic circuit.
CCD three kinds of filter module arrangement, the most commonly used arrangement on the left is G
CMOS three-layer color-sensing color imaging RGR arrangement
The earliest TV recording and playback system was a single receiving photoelectric group, and the interface was separately received with RGB trichromatic light filters. During playback, it also broadcasted black and white images with a single cathode ray tube, and then used RGB filters to intervene in color development. The TV signal is also a scanning signal. The denser the signal, the higher the frequency and the higher the resolution. The number of frequencies is called the bandwidth. 24 frames per second in film work, and 48 or 72 frames per second must be played, which can reduce the flicker of the picture (because of the increase in the persistence of vision), while the TV is shot at 25 or 30 frames per second, Playing at 50 or 60 frames during playback also reduces flicker. The black and white TV system is received at 25 or 30 frames per second, and played at 50 or 60 frames, but the color is played at 150 frames or 180 frames per second, that is, black and white is played at 3 times faster speed, and each frame accommodates RGB three. Signal, so the bandwidth of the color TV should be increased three times to be sufficient. On the contrary, the color system can play black and white images, but only once for each RGB. The signal of the TV is not the symmetrical signal of R, G, B, but the visual signal. The signal of the black and white contrast and the image is the main body. The redness + Greeness signal and the Yellowness + Blueness signal are used to make sharp black and white images. If the non-sharp color image is combined, the result is a visually sharp image. This RGB asymmetric signal requires only 50% of the bandwidth capacity of the RGB symmetric signal. There are PAL 625 scanning lines in the TV signal, with the main signal 6MHz and the sub signal 1.5MHz, a total of 7.5MHz, and the NTSC 480 line uses the main signal 4.0MHz plus 1.0MHz + 0.3MHz sub signal, so the PAL signal occupies a larger The bandwidth can be displayed. The French SECAM system is similar to the PAL system, except that the secondary signal has been changed. The SECAM system is used in France, French-speaking areas, French territories, and Russia. Japanese HDTV High Definiton Analog Telvison high-resolution TV, using 1125 lines, with 16: 9 appearance size, a total of 180 grids per color 60 grids RGB. At present, the LCD has a large size of 60? The mother-in-law is naughty? The master? The drink? The Xuanxiong squint? The incendiary of the incendiary? The shell rake? The address? Nalog HDTV has gradually developed. Electronic camera for color image reception, TV station uses advanced color video recorder, three CCDs are used, and these CCDs are black and white sensors, but before each CCD receives a full image, there are R, G, B three different color filters, After the color image enters the lens of this advanced video recorder, the received image is separated by two bipolar prism lenses, the first prism is reflected below B blue is received, and the green light directly leads to the CCD on the back of the camera to form a green image. The two bipolar prisms reflect the other image onto the red filter CCD above, which is combined into a complete RGB three-color image. Today's photoelectric receivers of digital cameras are divided into two categories: CCD and CMOS. CCD (Charge-Coupled Device electronic coupling device) is arranged in a plane grid-like CCD, and the three color filter combinations of R, G, and B are regularly coated. , Most of them are arranged in a checkerboard pattern with 50% G, 25% R, 25% B are also arranged in a more distant checkerboard pattern, and there are also three-color arrangement of C, M, and Y, each grid can accept two colored lights, Y accounts for 50%, 25% each of C and M are also arranged in a checkerboard. The other is that the four colors of C, M, Y and G are arranged in a checkerboard, G is an auxiliary signal, and all the imaging units of the CCD are the same The light received on a surface is different from the three-layer light receiving method of CMOS divided into B, G, and R. Therefore, after the CCD receives light, the image becomes a checkerboard pattern, and the image file must be reintegrated. The first type uses the G signal, the first The two types use the Y signal and the third composite Y + G signal as the main body to sort out the outline of the image. After completing the new logical calculation, there is a more reasonable but not necessarily accurate image. The bigger, to make up for the gap between the resolution of it and the chemical silver salt photosensitive negative film. The image pixel signal received by the unit cannot be directly transmitted. It must be pushed by one CCD to another CCD. It is pushed out from the back like a toothpaste to the exit of the toothpaste container before it is organized into an electronic signal. The loss and variation between them are also quite Many. CMOS is every pixel that receives the image. The signal is converted into an electronic signal by its own signal before it is collected by the line. The signal is more accurate. However, most digital cameras today use CCD as the photosensitive element, and only a few cameras use CMOS. The cost of mobile phones and the convenience of signal processing, coupled with the low pixel requirements, use CMOS as the photosensitive receiver. CMOS (Complementary Metal-Oxide Semiconductor supplementary metal oxide semiconductor), its imaging principle is like a color negative film is three-dimensional three-layer In the method, the uppermost B blue photosensitive layer, the middle layer G green photosensitive layer, and the lower red photosensitive layer, so the completed image has been completely separated, without re-integration processing like CCD, but the nominal resolution of Mb file value of CMOS , Often based on the CCD imaging ability to correspond to each other, if the image changes too small, CMOS can not be very precise Without losing the level of analysis, some manufacturers believed that the semiconductor process used for CMOS process was not limited by many imaging patent calculation methods ten years ago. It should have good development potential, but so far CMOS has not yet become a Mainstream digital camera image capture device. (Editors in this section have emphasized the principles and applications of CCD and CMOS to increase readability.)
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