Editing tones and colors: contrast and brightness
- Oct 23, 2019
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In addition, black-and-white processing also belongs to the range of tone and color processing, it can provide a variety of creative processing effect. If possible, you can also color the photos with color. Of course, you can choose the appropriate mode in the camera, but in almost all cases, the only way to achieve convincing results is to manually convert black and white accurately in the photo processing software.
There are two independent ways of photo processing: to adjust the color (creatively) and to transform the color photos into black-and-white photos perfectly. Both of them have their own charm, which requires photo processors to have corresponding technology, which can make them develop their own editing style and give their photos unique value.
Contrast and brightness
Concepts such as "color order", "curve" and "histogram" will be involved whenever it is concerned with optimizing image contrast. These concepts are closely related to photo processing and are not as complex and difficult as they sound. As long as you practice, you are likely to incorporate them into your standard process very soon. That's what you should do, because when you post-process a picture, making perfect tones is half the battle.
Is the contrast too low?
Learning to look at the histogram of a photograph can also help you before practicing that kind of eye. Histogram shows the number of brightness levels and the range of contrast in the image. Photoshop: Window Histogram | Photoshop Elements: Window Histogram | Paint-Shop Pro: View Panel Histogram | Gimp: Window dockable dialog Histogram Adjustment Histogram | Light: Window Panel Histogram Camera Raw: Histogram
In the histogram, the image with light color and insufficient contrast has a smaller range of color order, that is to say, there are unused brightness values at the left and/or right ends of the gray scale. In most cases, it is necessary to adjust the distribution of color order. In order to achieve the desired results, you should manually adjust it, rather than give it to any automatic function to perform. Only when the adjustment has to be done very quickly, or when you just want to have a rough look at the effect of the photo adjustment, but the specific implementation will still be done manually, can you consider the function of automatic adjustment. Photoshop: Image Automatic Tone Image Automatic Contrast Photoshop Elements: Enhancement Automatic Adjustment of Color Scale Enhancement Automatic Adjustment of Contrast PaintShop Pro: Adjustment Brightness and Contrast Column Map Equilibrium Gimp: Color Automatic Tone Equilibrium Color Auto Drawing Contrast Aperture Adjustment Color Level Automation Adjustment Curve Automation Lightroom: Modifying Photos Basic Tone Automation Camera Raw: Basic Adjustment Automation
Adjust contrast range
For smaller contrast ranges, you can adjust by expanding the histogram (also known as the extended color order), which is to readjust the distribution of the existing color order between black and white in the image. For this step, you can do it individually in each color channel or at the same time in all channels. In any common photo processing software, you can find the corresponding processing tools - these tools are usually put together with the histogram. Photohshop: Image Adjustment Color Level Image Adjustment Curve Photoshop Elements: Enhancement Adjustment of Illumination Color Level PaintShop Pro: Adjustment Brightness and Contrastiveness Column Map Adjustment Gimp: Color Color Level Curve Aperture: Adjustment Color Level
Pure black here represents the smallest dot (black dot) in the image that is as black as possible without any details. Pure white represents the brightest dot (white dot) in the image. These two brightness levels usually correspond to the contrast and brightness 141 of the lower 06 in the histogram. When extending the color scale of a dark and very flat photograph (left), you only need to move the two sliders in the histogram - the black slider on the left side and the white slider on the right side to the two ends of the curve to achieve a perfect horizon. Equilibrium order range (middle). If you continue to move the slider, you will define areas that are only darker or brighter as pure black or white. As a result, there are pure black areas and white areas (right) without details in the image. Two sliders on the surface: the black triangle and the white triangle, which can move horizontally along the gray scale.
Now in order to expand the contrast range of the image, you have to move the two sliders separately until they touch both ends of the curve. That is to say, the ideal contrast range is artificially generated. The darkest tone in the image is defined as black (brightness value is 0, used to set darkness), and the brightest tone is defined as white (brightness value is 255, used to set highlights).
In this step, you can judge by the naked eye, or hold the Alt key while moving: if you happen to be looking for a black spot, the image will be hidden, and you will only see a white area. If you move the black slider to the right, the first dark spot will appear at some point. When the dark spot is too small to be small, you stop and you will find the black spot. The same is true of the process of looking for white spots, but then you see a black area. You move the white slider to the left until the smallest spot appears. Then you find the white spot.
In addition, you can also set black and white spots directly and manually in the image. Most photo processing software has straws that you can use to mark the darkest or brightest points in the image. But it's not easy to find the right point (especially for color images). For a gray image or a part of a subject that is really black or white, such as a tire or a cloud, it is simpler to set points to ensure a complete range of color levels without the risk of color spillover.
For redefining pure black and white, it is important that you can really find the darkest and brightest points in the image. If the black slider moves to the right and exceeds the starting point of the curve, it will cause the so-called color spillover --- that is, not only one, but more than one brightness level of the color will become the new black. As a result, the farther you move the black slider to the right, the larger the "black inundated" area of the image without details. Similarly, white sliders can cut out bright areas in the image and make them pure white without details. Because in principle, the brightness value of all tones on the left side of the black slider is set to 0, and the brightness value of all tones on the right side of the white slider is set to 255.
The greater the difference between the original histogram and the complete histogram, the more fissures you will find in the new histogram after extending the chromatic order. According to different themes, these fissures are different in the viewer's view. The color transition belongs to the obvious victim of the extended color order. After the extended color order, the color with different brightness values may not be able to transition smoothly, that is to say, the adjacent colors can not merge with each other.
In this regard, all contrast adjustment tools can be used, because its operation steps are usually: to keep the position of black and white spots unchanged, only darker middle tones become darker, brighter middle tones become brighter. In this way, the middle tone moves a lot to the edge, and the difference between the darker and brighter middle tones is much greater - the contrast is improved.
As a result, instead of persuading people with soft, uniform color scales, you get images that give people higher clarity, clear outlines and overall appeal through higher contrast. Phtoshop: Image Adjustment Brightness / Contrast Contrast Image Adjustment Shadow / Highlight Image Adjustment Curve Photoshop Elements: Enhancement Adjustment Shadow / Highlight Intermediate Contrast Enhancement Adjustment Brightness / Contrast Contrast PaintShop Pro Adjustment Contrast Brightness / Contrast Contrast Adjustment Brightness and Contrast Curve Gimp: Color Brightness / Contrast Contrast Color Curve Aperture: Adjustment Enhancement Contrast Adjustment Room Light: Modify Photo Basic Tone Contrast Expansion Curve Basic Contrast | | Nik Software: Viveza Color Efex Pro Contrast Filter Name Color Efex Pro Color Contrast Color Efex Pro Tone Contrast
Adjust exposure and brightness
In many cases, in addition to adjusting the contrast, the overall brightness of the image has to be modified. When the photo is slightly overexposed or underexposed, or when you want to modify the image completely subjectively, you need to adjust the exposure and brightness of the photo, because the brighter image will look friendly, relaxed and positive without the subject, composition and other post-processing factors. Darker images, on the other hand, seem depressing, heavy and negative.
When dealing with photographs, you must make a clear distinction between adjusting exposure or brightness. Adjusting exposure is equivalent to raising or lowering the aperture level, which is to simulate another exposure. This means that all levels of the image will be moved to become brighter or darker than before, but the ratio between dark and bright tones remains unchanged. This kind of processing should be carried out with special caution, because they may cause color spillover, resulting in many areas without details in the image. Photoshop: Image Adjustment Exposure | Aperture: Adjustment Exposure Exposure | Lightroom: Modification of Photo Basic Tone Exposure | Camera Raw: Basic Exposure
Unlike the exposure adjustment, the brightness adjustment is only reflected in the middle tone. That is to say, black and white and the range of tones they determine remain unchanged and will not be affected by this adjustment, but the proportion between dark tones and bright tones will change. Specifically, the slider representing the middle tone will move left or right, which will cause the image to brighten or darken at the same time. Photoshop: image adjustment brightness / contrast brightness image adjustment color level image adjustment curve Photoshop Elements: enhancement adjustment of light brightness / contrast brightness enhancement adjustment of light color level PaintShop Pro: adjustment brightness and contrast brightness / contrast brightness| Adjustment Brightness and Contrast Brightness / Clarity Brightness Contrast Curve Gimp: Color Brightness / Contrast Brightness Curve Color Color Grade Aperture: Adjustment Exposure Brightness Curve Adjustment Color Grade Lightroom: Modification Basis Ben Tone Curve | Camera Raw: Basic Brightness Curve Parameter / Point | Nik Software: Viveza Color Efex Pro Name of Contrast Filter
Using Gamma Value
If you set the gray point to the black point, or define a darker tone in the image as the middle gray value (Gamma value & lt; 1), the bright tone will occupy more space, while the dark tone will be relatively less, and the image will brighten; if you shift the gray point to the pure white direction (Gamma value & lt; 1), the bright tone will occupy more space. The image will darken if the value of Ma is & gt; 1. However, in both cases, the range of color order of the image is the same. Photoshop: Image Adjustment Curve Image Adjustment Color Rank Image Adjustment Exposure Gray Coefficient Correction Photoshop Elements: Enhancement Adjustment of Illumination Color Rank PaintShop Pro: Adjustment Brightness and Contrastiveness Curve Gimp: Color Curve | Color Color Grade | | Aperture: Adjustment Curve Adjustment Color Grade | Lightroom: Modifying Photos Tone Curve | Camera Raw: Tone Curve Point | Nik Software: Viveza Software
Exhaust in it-curve
The most powerful, versatile and creative tool for adjusting exposure and contrast is probably curve, which you can find in many general photo processing software. Compared with other tools, the greatest advantage of curve is that it combines histogram-based work with the possibility of making the most accurate adjustments to contrast, exposure and brightness. This means that, in principle, you only need this tool for all the editing steps described previously. Photoshop: Image Adjustment Curve | PaintShop Pro: Adjustment Brightness and Contrast Curve Gimp: Color Curve Aperture: Adjustment Curve Lightroom: Modification of Photo Tone Curve Camera Raw: Tone Curve Parameter / Point Nik Software: Viveza
The curve is constructed as follows: the gray scale on the horizontal axis corresponds to the distribution of brightness value in the original image, and the longitudinal axis corresponds to the distribution of brightness value after editing. If you open the dialog box, you will see that the direction of the curve is always a standard diagonal line. That is to say, the curves before and after editing go the same way. At the same time, there is also a histogram of the image in the background of the curve. On the gray scale below, you can see a black triangle (slider) and a white triangle (slider), which can be moved at will. That is to say, you can expand the color order by moving two sliders (or pipettes) on the gray scale, and you can also modify the Gamma value.
You can also set marking points on the curve, which can be moved up, down, left or right at will. The area in the lower left corner corresponds to the dark tone in the image, the area in the upper right corner corresponds to the highlight, and the area in the middle corresponds to the middle tone. The results of the movement of a single point and the subsequent changes in the direction of the curve are as follows:
& nbsp; If the curve bends to the left, the overall brightness of the image will be improved, because the darker tones are now brighter.
These basic adjustments are very accurate and flexible because you can edit each tone area individually. This adjustment does not aim at a fixed hue value (the curve keeps a smooth trend), so it can also ensure that the transition between different hue areas is more natural. If a fixed point is set in the dark tone area and the curve of the middle tone and high light area is adjusted to S shape, the contrast of the two areas will be improved, while the dark tone will remain unchanged. In addition, the curve can handle each color channel separately.
Local brightening and darkening
Because the brightness distribution of different regions in an image is very different, it is sometimes necessary to selectively brighten or dim an image region when adjusting the brightness and contrast. As for which image regions should be selectively adjusted, it depends on the subject. When you're not sure whether a brighter image area is too bright, consider how important it is to the subject and the message it conveys. Because in principle, brighter areas attract viewers'attention and enter the "foreground" of great concern, while darker areas retreat into the "background". That is to say, the subject and main image elements of a photo should be emphasized through light and brightness, and the unimportant elements can be placed in darker areas or even shadows. If your theme is too dark, it is recommended that you highlight it partially. If the unimportant details are too bright to draw the viewer's attention away from the theme, you should dim them.
However, both brightening and darkening, especially for color photographs, have great disadvantages, because if the intensity of these operations is too high, it will leave a very obvious trace of processing. There is no such problem with black-and-white photographs. You can use these tools with great confidence, and the image effect will not seem unnatural at all.
Deepening and fading tools have a special purpose of generating and reducing the effect of dizziness. The concept of "vignetting" describes the gradual darkening of the image from the middle to the surroundings, which is actually related to the imaging characteristics of the lens used in shooting. Generally, the purpose of processing is to reduce or completely eliminate the halo effect produced during shooting. In this regard, you need to use the appropriate tools to brighten the darker areas. Photoshop: Tool Dodge Tool | | Photoshop Elements: Tool Dodge Tool | | PaintShop Pro: Tool Brightening / Darkening Brush | Gimp: Toolbox Dodge / Deepening Tool | Aperture: Adjustment Quick Brush Dodge | | Light Room: Modifying Photos Tool Adjusting Brush Exposure
Of course, consciously creating a halo effect will also be a very interesting processing step, which can attract the viewer's attention to the middle of the image, while obtaining a simulated, technical beauty. To create an artificial dizziness effect, you need to dim the edges and corners of the image. Photoshop: Tool Deepening Tool | Photoshop Elements: Tool Deepening Tool | PaintShop Pro: Tool Brightening / Darkening Brush | Gimp: Toolbox Mitigation / Deepening Tool | Aperture: Adjustment Quick Brush Etching Room | Light: Modifying Photos Tool Adjusting Brush Exposure
In addition to manual brightening or darkening image processing methods, you can also use many photo processing software with special tools designed for the function of vertigo. Photoshop: filter lens correction self-determination halo | Photoshop Elements: filter correction of camera distortion halo | PaintShop Pro: effect photo effect halo | Gimp: filter distortion lens error brightening | Aperture: adjustment halo adjustment halo shadow removal | room: photo modification Correction Manual Lens Dark Angle Repair Photos Effect Cut Dark Angle Camera Raw: Effect Cut Shadow Nik Software: Color Efex Pro Black Angle Filter Silver Efex Pro Complete Adjustment Black Angle
DRI and HDR
In contrast processing, you will inevitably encounter two concepts: dynamic range expansion (DRI) and high dynamic range (HDR). The purpose of these two adjustments is to expand the dynamic range of the image or to preserve a higher contrast in the image than can be accommodated by the camera sensor. For this reason, both methods require a series of photographs of the subject, and the photographs taken must be as same as possible in view. Therefore, mobile themes are not suitable for such shooting. Tripods must be used when shooting, and the depth of field should be set as same as possible, because only in this way can the brightness of the image change with exposure time.
In contrast, HDR images store all the light and shade information of the subject in a large image file with the suffix ".hdr". This is achieved by a special HDR software, which integrates the brightness levels of several photographs with different exposures, and then generates a photograph that contains much more brightness levels than ordinary photographs - in general, the color depth of each color channel is at least 32 bits. Such a large tonal range is close to all the color levels visible to the human eye, but this effect does not appear when the output media such as display, printer and so on are used to display, because these output media can only display 256 color levels. Therefore, HDR image is actually a "theoretical" image, which virtually collects as many brightness levels as possible, so it can be used to generate different versions of images like RAW files. Photoshop: File Automatic Merge to HDRPro | Photoshop Elements: Enhancement Photomerge Photomerge Exposure | PaintShop Pro: File HDR Exposure Merge | Nik Software: HDR Effect Software Merge | Professional Software: FDRTools | Luminace | Picturenaut | DRI Tool
After the HDR image is generated, the next necessary step is to convert the excessive tone range into a smaller, displayable tone range, which we call tone mapping or dynamic compression. In order to complete this process, there are various tools available. With these tools, you can decide which areas of the image to display, the brightness of the display, and to what extent the details are displayed, or which hue values can be discarded. Generally, all kinds of photo processing software will have at least a regulator for adjusting the exposure and Gamma value of the image. In addition, some software also provides tools for adjusting the color saturation, contrast and contrast distribution of images separately. To ensure that the conversion is as accurate as possible, in most cases, it is recommended to compress the color depth step by step, first to 16 or 12 bits, and then to 8 bits.
The goal of tone mapping is that the final image results can be as close as possible to the visual effect of the shooting in terms of contrast, brightness and color. But your creative space is totally Unlimited - you can also use unnatural colors and contrast to create an unusual world of light and shadow. Photoshop: File Automation Merge to HDR Pro | PaintShop Pro: File HDR Load HDR File | Nik Software: HDR Effect Software Tone Mapping | Professional Software: FDRTools Luminace Picturenaut DRI Tool