Convert RAW data with LightZone

Important Tools

LightZone first displays only two tools when you switch to the editor: RAW Adjustment and ZoneMapper. Although you can change both the order and the activity of all other tools, this is not allowed with RAW Adjustment: It always remain available, always comes first, and directly affects the entire image – regions are not possible. The tool includes five settings. You can control the basic exposure via Exposure; adjust the slider so that there are no "blown-out" highlights. You can reduce the color noise via Color Noise. In doing so, observe the image at a 1:1 fit, especially in the dark areas and monochrome bright areas.

You can influence the noise in the brightness using Grain_Noise; higher values blur the image. You can control the color temperature and thus the white balance using Temperature and Tint by using both sliders or by selecting a gray point in the image as a white balance reference with the pipette. Reset the adjustments by clicking the As Shot button.

Twelve standard tools lie in the tool tray under the preview window. Each tool opens its own window, in which you can make adjustments. The title bar provides information about the state of the tool: A triangle facing downward shows that the dialog for the settings is open. If this is followed by the regions symbol, the tool will not act on the whole image, but just on the enabled region.

The question mark leads to a small online help wizard for the current tool. Removing the check mark temporarily disables the tool without losing the current settings. You can remove the tool and all settings from the edit chain by clicking the X icon in the far right corner. To change the order of steps in the tray, grab them by the title bar and move them.

ZoneMapper

ZoneMapper acts as a central tool for LightZone. "Zone" refers to the Adams zones [2] for black and white photography created by the American nature photographer Ansel Adams to ensure optimal exposure, even in high-contrast scenes. This tool is enabled automatically when you switch to the editor but is locked by default. Left-click on the lock symbol and choose Unlock to change to the ZoneMapper's work mode. A reference grayscale of 16 tonal values is on the left, and to the right are modifiable "steps," which you can move arbitrarily.

For example, to optimize the reference white – the maximum image brightness – create a zone lock by selecting the highest step on the grayscale that still shows yellow in the preview. The yellow areas indicate where the image expresses that zone value. Next, move the edge of the zone to the upper edge of the grayscale, making the lightest areas of the image appear pure white. Do exactly the opposite for the black point: Here, the darkest areas of the image appear pure black as soon as you have moved the corresponding step to the lower edge (Figure 7).

Figure 7: The ZoneMapper always acts in combination with the ZoneFinder from the preview. This preview shows the zones in the images where the mouse pointer is located.

You can move each step arbitrarily in this way and thus change the brightness and the contrast of the whole image. Pushing together two steps reduces the contrast between them; spreading them increases it. You can delete any zone locks that are no longer needed by clicking the small x in the yellow box. It makes sense to start with as few steps as possible using ZoneMapper to keep a clear overview. You can then add additional steps, as required.

The Luminosity and RGB buttons under the grayscale change the color space in which you apply the zones system. If the image contains very rich (almost completely saturated) colors, you should use RGB; otherwise, Luminosity is the better option. You can also use multiple ZoneMappers at the same time in one image. This often works better than trying to make all adjustments in one ZoneMapper. A video tutorial [3] explains the procedure.

Relight Tool

The program's second important tool is Relight (Figure 8), which changes an image's exposure post hoc. Unlike ZoneMapper, which initially displays the brightness zones in the image unchanged, the Relight tool causes an immediate change of brightness when invoked. Although the ZoneMapper changes the brightness globally, Relight acts specifically on lights, shadows, and middle tones.

Figure 8: The Relight tool affects lights, shadows, and middle tones.

Five sliders control the tool's most important functions. You should test the tool in advance on several images – bright, dark, flat, high-contrast – to get a feel for the effect. Relight allows intuitive application with a little experience [4].

You will find two important groups of functions in the bottom part of the dialog: Tool Settings contains both the Invert Masks function described earlier and Blending Mods. They correspond to the layers modes in Gimp. You can adjust the opacity analogously via Tool Opacity. The Color Selection tab (Figure 9) controls the color range; the adjustments made here normally affect the entire image. However, LightZone provides the selection in both the RGB and Luminosity channels.

Figure 9: You have direct access to areas with particular characteristics via the Color Selection tab.

The selection is made by clicking on an item in the main window that corresponds to the colors and brightness you want. To do this, enable the pipette with a click; you can reset the adjustments with the button next to it. Using two checkboxes, you can control whether the selection should be made based on the shade (upper) or on the brightness (lower). Instead of All, you can set individual shades that you want to consider for the selection, as required. In the next step, you can change how softly a selection is made via Range and the three sliders under it.

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