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0001 .. meta:: 0002 :description: digiKam Image Editor Colors Tools 0003 :keywords: digiKam, documentation, user manual, photo management, open source, free, learn, easy, image, editor, color, depth, space, correction, auto, black, white, filters, emulation, infrared, invert, negative, balance, curves, levels, hue, saturation, lightness, channel, mixer 0004 0005 .. metadata-placeholder 0006 0007 :authors: - digiKam Team 0008 0009 :license: see Credits and License page for details (https://docs.digikam.org/en/credits_license.html) 0010 0011 .. _colors_tools: 0012 0013 Colors Tools 0014 ============ 0015 0016 .. contents:: 0017 0018 .. _color_depth: 0019 0020 Encoding Depth 0021 -------------- 0022 0023 Here you can change the encoding depth per color channel of the edited image. 8 bit encoding is the common JPEG format, 16 bit encoding is better suited for high quality images, but this format needs more storage space, calculation time and is currently available with PNG, PGF, TIFF, and JPEG-2000 formats only. 0024 0025 .. note:: 0026 0027 When you re-encoding an image from 8-bit to 16-bit, uniformly distributed noise is introduced to prevent histogram holes due to colors range expansion. 0028 0029 .. important:: 0030 0031 HEIF, AVIF, JPX formats can encode as 8 bits or 12 bit. WEBP is limited to 8 bits. These limitations can change in the future. 0032 0033 .. _color_cm: 0034 0035 Color Management 0036 ---------------- 0037 0038 This tool allows to convert image from one color space to another one. Its use is the change and assignment of color profiles to an image. For detailed instructions on the use of color profiles, please refer to :ref:`Color Management Rules <color_management>` and :ref:`Color Management Settings <cm_settings>` sections. 0039 0040 .. figure:: images/editor_profile_converter.webp 0041 :alt: 0042 :align: center 0043 0044 The Image Editor to Change Image Color Space 0045 0046 .. _color_auto: 0047 0048 Auto-Correction 0049 --------------- 0050 0051 This tool set provides five automatic correction levels that will improve an image in most cases. Use this tool before going into the more involved manual adjustments. 0052 0053 The **Auto Levels**, **Normalize**, **Equalize**, **Stretch Contrast**, and **Auto Exposure** available from :menuselection:`Color --> Auto-Correction...` menu entry menu will attempt to work out the best color levels automatically. You will need to experiment with the effects of these functions to see what works best with your photograph. 0054 0055 - **Auto Levels**: This option maximizes the tonal range in the Red, Green, and Blue channels. It searches the image shadow and highlight limit values and adjusts the Red, Green, and Blue channels to a full histogram range. 0056 0057 - **Normalize**: this method scales brightness values across the selected image so that the darkest point becomes black, and the brightest point becomes as bright as possible without altering its hue. This is often a “magic fix” for images that are dim or washed out. 0058 0059 - **Equalize**: this method adjusts the brightness of colors across the selected image so that the histogram for the Value channel is as flat as possible, that is, so that each possible brightness value appears at about the same number of pixels as each other value. Sometimes Equalize works wonderfully at enhancing the contrasts of an image. Other times it gives garbage. It is a very powerful operation, which can either work miracles on an image or destroy it. 0060 0061 - **Stretch Contrast**: this method enhances the contrast and brightness of the RGB values of an image by stretching the lowest and highest values to their fullest range, adjusting everything in between. This is noticeable only with washed-out images and can be a good fix-it tool for bad photographs. 0062 0063 - **Auto Exposure**: This option enhances the contrast and brightness of the RGB values of an image to calculate optimal exposition and black level using image histogram properties. 0064 0065 The results of any adjustments you make will not be remembered until you save your photograph. 0066 0067 .. figure:: images/editor_auto_corrections.webp 0068 :alt: 0069 :align: center 0070 0071 The Image Editor to Process Auto Color Corrections 0072 0073 Black and White Conversions 0074 --------------------------- 0075 0076 Black and White photography has always been fascinating in its abstraction capability. With the advent of digital photography, Black and White has almost become a desktop activity, as color images can be easily converted on the computer into black and white, even providing a set of vintage film roll profiles. This filter is also able to simulates traditional infrared film material. 0077 0078 .. _color_bw: 0079 0080 Legacy Films Emulation 0081 ~~~~~~~~~~~~~~~~~~~~~~ 0082 0083 digiKam comes with a couple of black & white filters that you can use on your photographs. Under the :menuselection:`Color --> Black & White...` menu you will find classic black & white chemical toning used in analog photography. The controls come on four drop-down items: **Film**, **Lens Filters**, **Tone** and **Luminosity** as shown on the screenshot below. Film, filters and color toning can be applied independently of each other (on top of each other). The filters actually influence the RGB channel mixing, whereas the toning purely adds a uniform monochromatic tint to the black & white photograph. In the lightness tab you will find a tonal adjustment tool (like curve adjust), a contrast tool and an over-exposure indicator to improve the Black and White rendering. 0084 0085 .. figure:: images/editor_bw_filters.webp 0086 :alt: 0087 :align: center 0088 0089 The Image Editor to Emulate Black and White Films 0090 0091 With **Film** setting, a specific settings allows to emulate a number of famous Black and White photographic films as: 0092 0093 - **Generic**. 0094 - **Agfa**: 200X, Pan 25, Pan 100, Pan 400. 0095 - **Ilford**: Delta 100, Delta 400, Delta 400 Pro 3200, FP4 Plus, HP5 Plus, PanF Plus, XP2 Super. 0096 - **Kodak**: Tmax 100, Tmax 400, TriX. 0097 0098 With **Lens Filters** setting, a color filter can be simulated as placed on front of lens: 0099 0100 - **No Lens Filter**: simulate black & white neutral film exposure. 0101 - **Green Filter**: simulates black & white film exposure with green lens filter. This comes good with all scenic images, especially suited for portraits taken against the sky (similar to 004 Cokin(tm) Green filter). 0102 - **Orange Filter**: simulates black & white film exposure with an orange lens filter. This will enhance landscapes, marine scenes and aerial photography (similar to 002 Cokin(tm) Orange filter). 0103 - **Red Filter**: simulates black & white film exposure with red lens filter. Creates dramatic sky effects and can simulate moonlight scenes in daytime (similar to 003 Cokin(tm) Red filter). 0104 - **Yellow Filter**: simulates black & white film exposure with yellow lens filter. Most natural tonal correction, improves contrast. Ideal for landscapes (similar to 001 Cokin(tm) Yellow filter). 0105 0106 With **Tone** setting, a color tint can be applied to the image: 0107 0108 - **Sepia Filter**: gives a warm highlight and mid-tone while adding a bit of coolness to the shadows - very similar to the process of bleaching a print and re-developing in a sepia toner (typical for your grandmothers photographs). Similar to 005 Cokin(tm) Sepia filter. 0109 - **Brown Filter**: similar to Sepia Tone filter, but less pronounced. 0110 - **Cold Filter**: start subtle and replicate printing on a cold tone black & white paper such as a bromide enlarging paper. 0111 - **Selenium Filter**: effect that replicates traditional selenium chemical toning done in the darkroom. 0112 - **Platinum Filter**: effect that replicates traditional platinum chemical toning done in the darkroom. 0113 0114 .. _color_infrared: 0115 0116 Simulate Infrared Film 0117 ~~~~~~~~~~~~~~~~~~~~~~ 0118 0119 Simulating classical infrared film material (the effect is rendered in black and white) is an interesting alienation effect that is even stronger and more dramatic than pure black and white conversion. Contrast and an abstract touch are improved, which can underpin the expression of the photographer as an artist. It is like taking an image in black and white with a red filter on the camera lense. Areas which reflect little red light, e.g. the sky, will show as low density, dark areas. Areas which are excellent reflectors of red light, e.g. most green foliage, will be high density areas. And snow landscapes are really dramatic. 0120 0121 .. figure:: images/editor_infrared.webp 0122 :alt: 0123 :align: center 0124 0125 The Image Editor to Emulate Infrared Films 0126 0127 The filter tries to reproduce the famous Ilford(tm) SFX and Kodak Tmax infrared film series. These films has a sensitivity range of 200-800 ISO: 0128 0129 - **Ilford**: SPX 200, SPX 400, SPX 800. 0130 - **Kodak**: HIE. 0131 0132 .. note:: 0133 0134 Because the filter mixes color channels to reproduce infrared film (with emphasis on green channel), one can not simulate infrared effect from Black and White original photograph, since the color information is missing. 0135 0136 .. _color_invert: 0137 0138 Inverting Colors 0139 ---------------- 0140 0141 In case of digitalize analog film with a scanner, color can appear inverted compared to the reality. This tool allows to reverse the colors into their respective `complementary colors <https://en.wikipedia.org/wiki/Complementary_colors>`_. 0142 0143 Invert color to a complementary color (or opposite color of color on the color wheel), consist to have cyan as the opposite color of red, yellow as opposite color for blue, and magenta as the opposite color of green. With :menuselection:`Color --> Invert` option, we can invert all the pixel colors and brightness values in the image, as if the image was converted into a negative. Dark areas become bright and bright areas become dark. Hues are replaced by their complementary colors. 0144 0145 .. _color_negative: 0146 0147 Simulate Negative Film 0148 ---------------------- 0149 0150 While digiKam is first and foremost an application for processing and organizing digital photos, it also features tools for working with `film negatives <https://en.wikipedia.org/wiki/Negative_(photography)>`_. 0151 0152 Before you can process negatives in digiKam, you need to digitize them. If you don’t have access to a film scanner or a lab that offers film scanning services, you can digitize film using a DSLR camera (there are plenty of tutorials on how to do that on the Web, as `this one <https://petapixel.com/2013/03/25/digitizing-your-film-using-your-dslr/>`_). The rest of the process assumes that you are using the latter way to digitize film negatives. 0153 0154 Open a RAW file containing a film negative in the editor. Crop the original file and apply lens correction if necessary. Choose then :menuselection:`Color --> Invert` to transform the negative into a positive image. In case you work with the color negative, the converted image most likely requires some additional tweaking. First of all, the converted image is likely to have a strong blue tint. The easiest way to remove it is to use digiKam’s **Auto-Correction** tool. Choose :menuselection:`Color --> Auto-Correction` and select one of the presets. In many cases, the **Auto Levels** or **Equalize** presets do a decent job of correcting the colors. If the colors still look slightly off, you can adjust them further using the :menuselection:`Colors --> Color Balance` tool. 0155 0156 .. figure:: images/editor_negative.webp 0157 :alt: 0158 :align: center 0159 0160 The Image Editor Tool to Simulate Negative Film 0161 0162 The **Invert** feature in combination with an **Auto-Correction** preset provides a quick-and-dirty way of converting negatives, but digiKam has another tool designed specifically for processing color negatives. To access it, choose the :menuselection:`Color --> Color Negative` menu entry. The Color **Negative** Film interface contains several handy features that can help you to convert the negative and tweak the resulting image. While the **Invert** tool uses a generic profile for converting negatives, the Color Negative Film interface offers profiles for many popular film types. So the first step is to select the appropriate profile. For better results, try to enable the **Color Balance** option, too. If the used film is not in the list, you can use the **Neutral** profile as a fall back. 0163 0164 Although choosing the matching film profile may yield a better result, the converted image may still require some work. In most cases, you may need to adjust the white point to remove the remaining blue tint. You can do this either manually or automatically using the appropriate tools. Usually, the automatic white point adjustment does the job, but the resulting image needs to be brightened up by adjusting the **Exposure** and the **Gamma** sliders. 0165 0166 .. _color_balance: 0167 0168 Colors Balance 0169 -------------- 0170 0171 Digital cameras often have problems with lighting conditions and it is not unusual to want to correct the color contrast and brightness of a photograph. You can experiment with altering the levels of different aspects of your photographs using the tools under the **Color** menu. You can see any adjustments you make reflected in the preview. When you are happy with the results, press **Ok** and they will take effect. 0172 0173 .. figure:: images/editor_colors_balance.webp 0174 :alt: 0175 :align: center 0176 0177 The Image Editor Colors Balance Tool 0178 0179 If your image is washed out (which can easily happen when you take images in bright light) try the **Hue/Saturation/Lightness** tool, which gives you four sliders to manipulate, for **Hue**, **Saturation**, **Vibrance**, and **Lightness**. Raising the saturation will probably make the image look better. In some cases, it is useful to adjust the lightness at the same time. *Lightness* here is similar to *Brightness* in the **Brightness/Contrast/Gamma** tool, except that they are formed from different combinations of the red, green, and blue channels. 0180 0181 When you take images in low light conditions, you could get the opposite problem: too much saturation. In this case the **Hue/Saturation/Lightness** tool is again a good one to use, only by reducing the saturation instead of increasing it. You can see any adjustments you make reflected in the preview image. When you are happy with the results, press Ok and they will take effect. 0182 0183 .. _color_curves: 0184 0185 Adjust Curves 0186 ------------- 0187 0188 The digiKam Adjust Curves is a tool to non-linearly adjust luminosity graduation and color channels. 0189 0190 The Adjust Curves tool is the most sophisticated tool available to adjust the images' tonality. Start it from the :menuselection:`Color --> Curves Adjust...` Image Editor menu. It allows you to click and drag control points on a curve to create a free function mapping input brightness levels to output brightness levels. The Adjust Curves tool can replicate any effect you can achieve with **Brightness/Contrast/Gamma** or the **Adjust Levels** tool, though it is more powerful than either one of them. But this tool can do more for you, it helps you to improve the tonal quality of your photographs to very finely stepped gray scales. And do not forget that the better the photographs are (good exposure, lossless format, 24 or 32 bit deep) the more you can improve them. Navigate to the "Achieving ultimate tonal quality" section of this instructive page: `Tonal quality and dynamic range in digital cameras by Norman Koren <http://www.normankoren.com/digital_tonality.html>`_. Use Adjust Curves tool to do just the same. 0191 0192 This tool provides visual curves to modify the intensity values of the active layer displayed as a histogram non-linearily. In **Curve smooth mode**, you change the curves shape by adding new points to the curve or by moving end point positions. Another way, is to draw all the curve manually in **Curve free mode**. In both cases the effect is immediately displayed in the image preview area to the left, where the preview can be configured by clicking on the top left icons. 0193 0194 .. figure:: images/editor_curves_adjust.webp 0195 :alt: 0196 :align: center 0197 0198 The Image Editor Adjust Curves Tool 0199 0200 To the left, half of the original and the target preview image is shown. The target preview is updated dynamically according to the widget settings. On the right side the following options are available: 0201 0202 - Modify **Channel**: with this combo box you can select the specific channel to be modified by the tool: 0203 0204 - **Luminosity**: changes the intensity of all pixels. 0205 0206 - **Red**: changes the Red saturation of all pixels. 0207 0208 - **Green**: changes the Green saturation of all pixels . 0209 0210 - **Blue**: changes the Blue saturation of all pixels. 0211 0212 - **Alpha**: changes the transparency of all pixels. 0213 0214 - Next to this box are two icons to select **Linear** or **Logarithmic** **Histogram** display. For images taken with a digital camera the linear mode is usually the most useful. However, for images containing substantial areas of constant color, a linear histogram will often be dominated by a single bar. In this case a logarithmic histogram will be more appropriate. 0215 0216 - **Main Curves Editing Area**: the horizontal bar (x-axis) represents input values (they are value levels from 0 to 255). The vertical bar (y-axis) is only a scale for output colors of the selected channel. The control curve is drawn on a grid and crosses the histogram diagonally. The pointer x/y position is permanently displayed above the grid. If you click on the curve, a control point is created. You can move it to bend the curve. If you click outside the curve, a control point is also created, and the curve includes it automatically. So each point of the curve represents an 'x' translated into a 'y' output level. 0217 0218 - Curve **Type** for channel: below the editing area are several icons that determine whether the curve can be edited using **Curve smooth mode** or **Curve free mode**. Smooth mode constrains the curve type to a smooth line with tension and provides a realistic rendering. Free mode lets you draw your curve free-hand with the mouse. With curve segments scattered all over the grid, result will be surprising but hardly repeatable. A **Reset to defaults** button is also available. If, for example, you move a curve segment to the right, i.e. to highlights, you can see that these highlights are corresponding to darker output tones and that image pixels corresponding to this curve segment will go darker. With color channels, moving right will decrease saturation up to reaching complementary color. To delete all control points (apart from both end points), click on the **Reset** button. To delete only one point, move it onto another point. Just ply with the curves and watch the results. You even can solarize the image on part of its tonal range. This happens when the curve is inverted in some part. The original photo preview has a red marker on it. If you place this marker to a zone you want to modify, a corresponding line will be drawn on the curve grid indicating the original value. Create a point on that line and move it up or down to adjust it to your pleasing. 0219 0220 - **Save As** and **Load**: these buttons are used to do just that. Any curves that you have set can be saved to the filesystem and loaded later. The used file format is The Gimp Curves format. 0221 0222 - **Reset**: this button resets all curve values for all channels. 0223 0224 The curves tool has several features that facilitate the positioning of points on the control curves. Clicking the mouse button in the original image preview area produces a vertical doted bar in the graph area of the curves tool. The bar position corresponds to the pixel value the mouse cursor is over in the image window. Clicking and dragging the mouse button interactively updates the position of the vertical bar. In this way, it is possible to see where different pixel values in the image are located on the control curve and helps to discover the locations of shadow, midtone, and highlight pixels. 0225 0226 Using this way and the three **Tone Color Picker** buttons will automatically create control points on the curve in all channels for shadow, middle, and highlight tones. Enable the color picker button that you want to use, and click on the original image preview area to produce control points on each of the Red, Green, Blue, and Luminosity control curves. 0227 0228 .. _color_levels: 0229 0230 Adjust Levels 0231 ------------- 0232 0233 The digiKam Adjust Levels is a tool to manually adjust the histogram channels of an image. 0234 0235 Situated between the more sophisticated Adjust Curves tool and the simpler **Brightness/Contrast/Gamma** Image Editor tool is this Adjust Levels tool for improving exposure. Although the dialog for this tool looks very complicated, for the basic usage we have in mind here, the only part you need to deal with is the **Input Levels** area, concretely the three sliders that appear below the histogram. 0236 0237 This widget contains a visual graph of the intensity values of the active layer or selection (histogram). Below the graph are five sliders that can be clicked into and dragged to constrain and change the intensity level for the image. The left sliders position represents the dark areas and similarly, the right position represents the light areas. 0238 0239 .. figure:: images/editor_levels_adjust.webp 0240 :alt: 0241 :align: center 0242 0243 The Image Editor Adjust Level Tool 0244 0245 Actually the easiest way to learn how to use it is to experiment by moving the three sliders around, and watching how the image is affected. 0246 0247 On the right, both an original and a target preview image is available. The target preview is updated dynamically according to the slider positions. On the left, the following options are available: 0248 0249 - Modify levels for **Channel**: this combo box allows the selection of the specific channel that will be modified by the tool: 0250 0251 - **Luminosity**: this option makes intensity changes against all pixels in the image. 0252 0253 - **Red**: this option makes Red saturation changes against all pixels in the image. 0254 0255 - **Green**: this option makes Green saturation changes against all pixels in the image. 0256 0257 - **Blue**: this option makes Blue saturation changes against all pixels in the image. 0258 0259 - **Alpha**: this option makes transparency changes against all pixels in the image. 0260 0261 - Set **Scale** for channel: this combo controls whether the histogram will be displayed using a linear or logarithmic amplitude. For images taken with a digital camera, the linear mode is usually the most useful. However, for images that contain substantial areas of constant color a linear histogram will often be dominated by a single bar. In this case a logarithmic histogram will often be more useful. 0262 0263 - **Input Levels**: the input levels allow manual adjustments to be selected for each of the ranges. The main area is a graphic representation of image dark, mid and light tones content. They are on abscissa from level 0 (black) to level 255 (white). Pixel number for a level is on ordinate axis. The curve surface represents all the pixels of the image for the selected channel (histogram). A well balanced image is an image with levels (tones) distributed all over the whole range. An image with a predominant blue color, for example, will produce a histogram shifted to the left in Green and Red channels, manifested by green and red color lacking on highlights. The level ranges can be modified in three ways: 0264 0265 - Three sliders: the first on the top for **Dark Tones*, the second one for **Light Tones*, and the last one on the bottom for **Midtones** (often called **Gamma** value). 0266 0267 - Three input boxes to enter values directly. 0268 0269 - Three **Color Picker** buttons using the original photo preview to automatically adjust inputs levels settings for shadow, midtone and highlights. There is also a fully automated adjustment button available next to the reset button. 0270 0271 - **Output Levels**: the output levels allow manual selection of a narrowed-down output level range. There are also two sliders located here that can be used to interactively change the output levels like Input Levels. This output level compression may, for example, be used to create a bleached image as a background for some other subject to put into the foreground. 0272 0273 - **Auto**: this button performs an automatic setting of the levels based on the pixel intensities of the image. 0274 0275 - **Save As** and **Load**: these buttons are used to do just that. Any Levels that you have set can be saved to the filesystem and loaded later. The used file format is compatible with **The Gimp** Levels format. 0276 0277 - **Reset All**: this button reset all Input Levels and Output Levels values for all channels. 0278 0279 The Adjust Levels tool has several features to facilitate the positioning input levels sliders. Clicking the mouse button in the original image preview area produces a vertical doted bar in the graph area of the histogram. The bar position corresponds to the pixel value under the mouse cursor in the image window. Clicking and dragging the mouse button interactively updates the position of the vertical bar. In this way it is possible to see where different pixel values in the image are located on the input levels sliders and helps to discover the locations of shadow, midtone, and highlight pixels. 0280 0281 Using in this mode and the three **Color Picker** buttons will automatically adjust input levels settings in all channels for shadow, middle, and highlight tones. Enable the color picker button that you want use, and click on the original image preview area to set input levels on each of the Red, Green, Blue, and Luminosity histogram channels. 0282 0283 **Over Exposure Indicator** option checks all color channel to see if more than one channel in a pixel is over-exposed, and you will see the combined color resulting of channel level settings. This feature is available as an indicator in the target preview area and has no effect on final rendering. 0284 0285 .. _color_bcg: 0286 0287 Correcting Exposure 0288 ------------------- 0289 0290 The simplest tool to use is the **Brightness/Contrast/Gamma** tool. It is also the least powerful, but in many cases it does everything you need. This tool is often useful for images that are overexposed or underexposed; it is not useful for correcting color casts. The tool gives you three sliders to adjust, for **Brightness**, **Contrast** and **Gamma**. You can see any adjustments you make reflected in the preview image. When you are happy with the results, press **Ok** and they will take effect. 0291 0292 .. figure:: images/editor_bcg_adjust.webp 0293 :alt: 0294 :align: center 0295 0296 The Image Editor Tool Correcting Exposure 0297 0298 .. note:: 0299 0300 Another important tool called **Levels Adjust** provides also an integrated way of seeing the results of adjusting multiple levels and also enables you to save level settings for application to multiple photographs. This can be useful if your camera or scanner often makes the same mistakes and you want to apply the same corrections. See the dedicated :ref:`Adjust Levels manual <color_levels>` for more information. See also a way of correcting exposure problems using the **Adjust Curves** tool. 0301 0302 .. _color_hsl: 0303 0304 Correcting Colors 0305 ----------------- 0306 0307 This tool is used to adjust hue, saturation, and lightness levels on a range of color weights for the current image. You can access the tool by the menu entry :menuselection:`Color --> Hue/Saturation/Lightness` 0308 0309 The tool settings are listed below: 0310 0311 - A Hue / Saturation color map to select visually the respective primary color to adjust. Just move and click with the mouse to set **Hue** and **Saturation** values in sliders below the map. 0312 0313 - **Hue**: The slider allow you to select a hue in the color circle (-180, 180). 0314 0315 - **Saturation**: The slider allow you to select a saturation (-100, 100). 0316 0317 - **Vibrance**: The slider allow you to adjust the vibrance of the image. Vibrance performs selective saturation on less saturated colors and avoiding skin tones. 0318 0319 - **Lightness**: The slider allows you to select a luminosity value (-100, 100). Lightness changes here concern a color range, while they concern a color tone with **Curves Adjust** and **Levels Adjust** tools, which work on color channels. If you change the Red lightness with this tool, all red pixels will be changed. With **Curves Adjust** and **Levels Adjust** tools, only dark, bright, or medium pixels luminosity will be changed. 0320 0321 You can see any adjustments you make reflected in the preview image. When you are happy with the results, press **Ok** and they will take effect. 0322 0323 .. figure:: images/editor_hsl_adjust.webp 0324 :alt: 0325 :align: center 0326 0327 The Image Editor Tool Correcting Colors 0328 0329 .. _color_mixer: 0330 0331 Channel Mixer 0332 ------------- 0333 0334 The digiKam image Channel Mixer is a tool to remix the color channels to improve or modify the photograph color shades. 0335 0336 The Channel Mixer is an another sophisticated tool to refine the images' tonality. Start it from the :menuselection:`Color --> Channel Mixer` Image Editor menu. 0337 0338 .. figure:: images/editor_channel_mixer.webp 0339 :alt: 0340 :align: center 0341 0342 The Image Editor Channel Mixer Tool 0343 0344 With the channel combo box you select and display the histogram per color. It gives a first hint of how to correct the channels by their relative distribution and amplitude. The left half of the dialog window always shows a preview of what you are doing. The original for comparison can be seen when selecting its own window tab. 0345 0346 The target photo preview has a red marker available. If you place this marker somewhere in the image, a corresponding vertical bar will be drawn in the histogram indicating the color level value in the current channel selected. 0347 0348 Now the controls are to the lower right: **Red**, **Green** and **Blue** slider controls enable you to mix the channels. If you check **Preserve Luminosity** the image will retain its overall luminosity despite you changing its color components. This feature is particularly useful when you also ticked the **Monochrome** box. Because the channel mixer is the tool to make great Black and White conversions of your photographs. Try to reduce the green channel for Black and White portraits. 0349 0350 .. note:: 0351 0352 Sometimes, especially when doing **Monochrome** mixing, reducing one color channel may increase visible noise, which actually originates in the chroma noise. Chroma noise means that the little noise specs do not appear at the same location in all the color channels, but the noise patterns looks different in every channel. If that is the case you can improve the monochrome conversion by reducing the chroma noise first. 0353 0354 **Save As** and **Load** buttons are used to do just that. Any mixer settings that you have set can be saved to the filesystem and loaded later. The used file format is The Gimp channel mixer format. 0355 0356 **Over Exposure Indicator** option adds up the colors if more than one channel in a pixel is over-exposed, and you will see the combined color resulting of channel gain settings. This rule is applying to target preview area and haven't effect to final rendering. 0357 0358 **Reset All** button resets all channel mixer settings to default values. 0359 0360 .. _color_wb: 0361 0362 White Balance 0363 ------------- 0364 0365 The digiKam White Balance is a semi-automatic tool to adjust the white-balance of a photograph. 0366 0367 White Balance setting is a common hurdle for digital still cameras. In the 'good old time' of film rolls, the white balance was done by the photolab. Nowadays the poor little camera has to guess what is white and what is black. Most of the time, what the camera chooses as the white point, is not of the correct shade or hue. Using this tool it is easy to correct this problem. It provides a variety of parameters that can be trimmed to obtain a better result. 0368 0369 .. figure:: images/editor_white_balance.webp 0370 :alt: 0371 :align: center 0372 0373 The Image Editor White Balance Tool 0374 0375 .. note:: 0376 0377 Even if the White Balance correction is not limited to 8 bit per channel, if you depart too much from the original, over exposure zones may appear. If you can adjust the White Balance in RAW conversion mode, the margin for correction will be greater as it processes correction while demosaicing. 0378 0379 The preview window can be resized. To the left, both an original and a target preview tab is shown. The target preview is updated dynamically according to the tool's settings. If you want to see the original White Balance, just click on that tab. 0380 0381 The target photo preview has a red marker available. The luminosity value of the pixel under the marker is shown as a vertical line in the histogram . 0382 0383 To the top right, the widget displays a histogram that is dynamically updated when changing the parameters. This histogram is very instructive as it shows that even in well exposed photos, most of the pixels have very small luminosity. With a button you can select to show either one of the 3 colors (or the sum of it which is called luminosity). 0384 0385 With **Exposure** you can digitally change the original photo exposure. Increasing the exposure is has the risk of making the pixel noise more visible and to blow out the highlights. Check the **Over exposure indicator** at the lower right to see if you run into saturation problems. The **Black Point** adjustment can be used to cut the histogram from the left. If your photograph looks foggy (histogram has empty space on the left, black side), you probably need to use this option. The **Exposure** and **Black Point** adjustments can be automatically estimated by pressing the **Auto Exposure Adjustments** button. This sets the black point quite accurately. 0386 0387 The contrast of your output depends on **Shadows**, **Saturation**, and **Gamma** parameters. The **Shadows** adjustment lets you enhance or diminish the shadow details in your photo. 0388 0389 Increasing the contrast of your photograph can have the side effect of reducing the apparent **Saturation** of the photo. Use a value larger than 1 to increase the saturation and a value of less than 1 to desaturate the photo. A value of 0 will give you a black and white photo. Don't be shy to bump up the saturation of your photos a little. The general rule is that for higher Contrast (lower **Gamma**) you need to apply more **Saturation**. 0390 0391 The next set of options is the mainstay of White Balance settings, which controls the ratio between the three color channels. Here you can set the color **Temperature**, making your image warmer or colder. Higher temperature will result in a warmer tint. Setting the ratio between the three color channels requires two adjustments. Since the temperature adjustment mostly controls the ratio between the red and the blue channels, it is natural that the second adjustment will control the intensity of the **Green** channel. 0392 0393 Instead of fiddling around with the above controls, you can simply use the **Temperature Tone Color Picker** button. Press on this button and click anywhere on the original preview image to get the output color of that area to calculate the white color balance temperature settings. This way, **Temperature** and **Green** values are automatically computed. 0394 0395 In addition you can set the White Balance using the preset list. These are the white color balance temperature presets available: 0396 0397 =================== =========================================================== ======= 0398 Color Temperature Description Kelvin 0399 =================== =========================================================== ======= 0400 **40W** 40 Watt incandescent lamp. 2680 0401 **200W** 200 Watt incandescent lamp, studio lights, photo floods. 3000 0402 **Sunrise** Sunrise or sunset light. 3200 0403 **Tungsten** Tungsten lamp or light at 1 hour from dusk or dawn. 3400 0404 **Neutral** Neutral color temperature. 4750 0405 **Xenon** Xenon lamp or light arc. 5000 0406 **Sun** Sunny daylight around noon. 5500 0407 **Flash** Electronic photo flash. 5600 0408 **Sky** Overcast sky light. 6500 0409 =================== =========================================================== ======= 0410 0411 **Color Temperature** is a simplified way to characterize the spectral properties of a light source. While in reality the color of light is determined by how much each point on the spectral curve contributes to its output, the result can still be summarized on a linear scale. This value is useful e.g. for determining the correct white balance in digital photography, and for specifying the right light source types in architectural lighting design. Note, however, that light sources of the same color (metamers) can vary widely in the quality of light emitted. 0412 0413 Low Color Temperature implies more yellow-red light while high color temperature implies more blue light. Daylight has a rather low color temperature near dawn, and a higher one during the day. Therefore it can be useful to install an electrical lighting system that can supply cooler light to supplement daylight when needed, and fill in with warmer light at night. This also correlates with human feelings towards the warm colors of light coming from candles or an open fireplace at night. Standard unit for color temperature is Kelvin (K). 0414 0415 **Over Exposure Indicator** option adds up the colors if more than one channel in a pixel is over-exposed, and you will see the combined color resulting of White Color Balance controls settings. This rule is applied to target preview area as an indication only and has no effect on the final rendering. 0416 0417 **Save As** and **Load** buttons are used to do just that. Any White Color Balance settings that you have set can be saved to the filesystem in a text file and loaded later. 0418 0419 **Reset All** button resets all filter settings to default values corresponding to Neutral White Balance color. Attention, even the neutral setting might be different from your original photograph. If you save it, the white balance will be changed.