Levels and Color Tool

The Levels and Color Tool is closely related to the Levels and Color transformation in that it lets you apply the same set of color and brightness adjustments to its input image. The big difference between the tool and the transformation versions is that the tool lets you paint the changes onto the output image using a brush while the transformation applies the changes to the entire image or, more precisely, to the masked parts of it. For this reason, the Levels and Color Tool has both brush and levels and color settings.

While you can get a similar effect using the transformation instead of the tool by using a mask and the Mask Brush Tool, the tool lets you see changes as you make them directly on the output image.

The Levels and Color Tool maintains an internal mask layer for the input image which is, in fact, what you are painting on. This mask layer records the location of all of your brush strokes so that adjustments you make to the brightness or color of the image can be made even after the strokes have been drawn.

Amount

The amount control lets you scale back the overall paint transparency or you can create a mask to restrict painting to specific parts of the image.

Mask Transparency

The Mask Transparency tool bar lets you select whether to display the output image or the mask that determines what part of the output image will be affected. In addition, you can control the transparency and color of the mask if you choose to display it.

Selecting the first button makes the mask fully transparent and displays the output image with no mask overlay. This setting lets you see the effects of each stroke as you make it and is automatically selected when you adjust any of the Levels and Color settings on the right side of the dialog box.

Selecting one of the other buttons displays the mask instead of the output image as an overlay on the input image. Different buttons display the mask with different levels of transparency while the rightmost button displays just the mask. High mask transparency makes it easier to see the image under the mask while low mask transparency makes it easier to see the details of the mask. Use one of these settings when you want to see where the brush is being applied to the image -- this helps you see any areas you might have accidentally overlooked and also helps you judge how strongly evenly the brush is being applied.

When you click OK or Cancel, if the mask transparency is set to display a color overlay on the input image or to display the mask only, it is reset to 100% transparent to show just the output image.

Mask Color

The Mask Color tool bar lets you set the color of the mask overlay, assuming the mask is not fully transparent.

Undo/Redo

The Undo tool bar lets you undo paint operations, one stroke at a time. A stroke is defined as everything between pressing the mouse button and releasing it. Undo and Redo affect only brush strokes and not the levels and color settings.

If the undo or redo button is grayed, it means there are no operations left to undo or redo. If you undo too many operations by accident, you can click the redo button until you get back to where you wanted to be. However, once you draw a new stroke, you can no longer redo past that point.

You can use the keyboard shortcuts Ctrl-Z for Undo and Ctrl-Y for Redo.

Brush Settings

The following settings determine the brush properties:

Radius

This slider controls the radius of the brush in pixels. Smaller brushes are good for creating fine detail. Larger brushes are good for filling big areas quickly. In addition to using the radius slider, you can also use the mouse scroll wheel to adjust the radius.

Transparency

This slider controls the transparency of the brush. The more transparent the brush, the more the background shows through.

Softness

This slider lets you control how soft the edges of the brush are. The softer the brush, the more smoothly its effects are blended with the original image.

Spacing

This slider lets you control the spacing interval at which the brush is applied as you drag. The smaller the spacing, the more the applications overlap. Too much overlap can lead to a heavier application of the brush than you intended, so you may need to increase the transparency. Too little overlap can leave gaps.

Fadeout

This slider lets you make the brush effect fade out as you draw each stroke, effectively increasing its transparency the further you drag from the starting point.

Shape

The brush shape tool bar has three options: round, square or diamond. Usually a round brush is fine, but occasionally a different brush shape helps you get into corners hard to reach with a round brush.

Mode

These settings control how the mask painting operation is performed.

Accumulate -- in this mode, the more you paint over an area, the more strongly the mask is applied. Overlapping strokes are added together. Since strokes are built up by applying circular brush masks offset by the Spacing setting, you will need to use a higher brush transparency in this mode to produce subtle effects.

Don't Accumulate -- in this mode, overlapping strokes stay as strong as the strongest one. Using this mode, you can use lower brush transparency settings to get subtle effects.

Erase -- in this mode, strokes you apply are subtracted from the current mask, reducing the effect on the output image.

Brush

If you select Single, then a single brush application is performed when you click on an image and is not repeated as you move the cursor with the mouse button depressed. The default setting is Continuous which keeps painting so long as you hold the mouse button down.

Stylus Pressure

If you are using a pressure-sensitive stylus, this control lets you determine the effect, if any, that stylus pressure has on the current brush stroke. If you are not using a tablet, this control is set to Ignore and the other options are grayed out.

Ignore -- stylus pressure has no effect.

Controls Opacity -- increasing stylus pressure reduces transparency, making the stroke more opaque.

Controls Radius -- increasing stylus pressure increases the brush radius, making it larger.

Controls Hardness -- increasing styles pressure reduces softness, making the edges of the brush harder.

Controls Flow -- increasing stylus pressure reduces spacing, causing the brush to be applied more often as you move the stylus.

Brush Display

As a visual aid, a representation of the current brush is displayed at the bottom of the dialog box. This display illustrates the radius, transparency, shape and softness of the brush. If you select a very large brush radius, part of the brush may not be visible.

Levels and Color Settings

Changes to the following settings apply to all the areas in the output image where you have painted on the mask layer. While you can apply multiple strokes, the same adjustments are made to all of them. If you want to make different adjustments to different areas of the image you need to use a separate transformation. When you alter any of these settings the colored mask overlay is automatically removed so you can see the effect of the changes.

Midtones

Adjusting this slider lightens or darkens the mid-tones of the image without affecting its shadows or highlights. You can control the brightness levels of the shadows and highlights using the Contrast and Dynamic Range controls (see below).

Contrast

Adjusting this slider increases or decreases the mid-tone contrast of the image at the expense of some loss of shadow or highlight detail. You should recheck your contrast setting after making a change to the Dynamic Range control since these two settings are closely related.

Dynamic Range

Adjusting this dynamic range slider alters the highlight brightness and shadow darkness of the input image. The original light and dark points in the input image are marked with small tic marks under the slider. You change the highlight brightness of the image by dragging the white slider and you change the shadow darkness by dragging the black slider. Moving the black and white sliders toward each other reduces image contrast; moving them apart increases it.

Setting the black (shadow) slider to 0% forces the darkest parts of the input image to be pure black while still preserving shadow detail. If you move the black slider beyond this point to the left into negative values, the result image will continue to become darker by making more and more of the shadow areas black as well. The effect is often more dramatic at the expense of shadow detail.

Setting the white (highlight) slider to 100% forces the lightest parts of the input image to be as bright as possible while still preserving highlight detail. The effect depends considerably on the color space you have selected (see above). If you move the white slider beyond this point to the right to values greater than 100%, the result image will continue to become lighter by setting more and more of the highlight areas to maximum brightness as well. This creates an effect of intense brightness at the expense of highlight detail.

As a shortcut, Shift-Clicking on the slider sets the range to 0% .. 100%. Ctrl-clicking on the slider resets the black and white points to line up with the tic marks.

Color Balance

This control alters the color balance of the image by applying a color filter to it. You can set the color balance in two ways: by clicking on the input image window or by selecting a color using the color picker.

Shift-clicking on the input image window samples the color of the input image at the point you click and sets the color balance to the complement of that color. This has the effect of neutralizing in the result image the color you select in the input image. Thus, if you can find a spot in the input image that should be a neutral gray, clicking on it will automatically compute the correct color filter to apply to the image to achieve this effect.

If you prefer, you can click on the small square that makes up the Color Balance color control bring up a color picker . You can use this control to specify a filter color directly from the color wheel or the filter bank.

If the input image is black and white, you can use the color balance control to tint it. For a more powerful way to tint black and white images, see the Tint transformation

Saturation

Adjusting this slider alters the saturation of the image. Moving the slider to the right increases the saturation; moving the slider to the left decreases the saturation. Moving the saturation slider all the way to the left yields a black and white image. Moving it all the way to the right produces an image with unnaturally intense colors. Placing the slider in the middle leaves the saturation of the input image unchanged. The Saturation slider is not displayed if the input image is black and white.

Color Space

If the input image is color then this control lets you select whether you want to work in the HSV or HSL color space. When you lighten an image using HSL, it becomes whiter and may appear washed out. When you lighten an image using HSV, it retains the relative proportions of its red, green and blue color components, but is limited in how bright it can get by the value of the largest RGB channel.

If the input image is black and white, then the Color Space control is not displayed.

Tips

To see the effects of the brush instead of the mask, click the leftmost Mask Transparency button or adjust one of the Levels and Color Settings. To see the mask instead of the effects of the tool, click one of the other Mask Transparency buttons.

Painting with a high brush transparency lets you build up the mask layer gradually and gives you more control over the mask. If you use Accumulate mode, you will need to use a higher transparency than if you use Don't Accumulate mode, and it will be harder to produce subtle effects or make masks cover larger areas evenly. However, if you use Don't Accumulate, painting over the same area repeatedly will not make the mask any stronger.