Levels
Adjusts the tonal range with input/output levels and gamma, per-channel or master.
Levels is the basic tonal adjustment. A value at Input Black becomes Output Black, a value at Input White becomes Output White, and Gamma bends the midtones between them (below 1.0 darkens, above 1.0 brightens).
The Channel buttons pick what the rows adjust: Master moves Red, Green, and Blue together, and Red, Green, Blue, and Alpha each adjust one channel on top of Master. The histogram at the top shows every color channel and updates live as you drag. On a batch it draws the frame the Preview shows. A single-channel image shows Master only and stays single-channel. A dot on a channel button marks each channel with changes, so a value set on Red, Green, or Blue is never hidden behind Master.
Auto and Normalize
Section titled “Auto and Normalize”The Auto section, below the channel rows, sets the levels from the image for you.
- Contrast stretches the tone and keeps colors as they are. It sets Master’s Input Black and Input White.
- Contrast and Color also removes a color cast: it sets the Red, Green, and Blue rows separately, with a gamma for each, so the near-neutral midtones land on neutral gray. It needs a color input, so it is unavailable on a mask. In a narrow panel its button reads Color.
- Clip is how much of the darkest and lightest pixels the two Auto buttons ignore at each end, from 0 to 5% (0.1% to start with), so a few stray pixels, such as one hot highlight, cannot set the range. It is saved with the node and changes nothing until you press an Auto button.
- Normalize maps the darkest value in the image to black and the brightest to white, with nothing ignored. It is the button earlier versions called Auto Levels, and it works as before. On a 32-bit (Float) image it reads the true minimum and maximum, so a depth pass or an HDR photo with values past 1.0 normalizes to 0 to 1 instead of clipping. It suits data where every value counts; for a photo, Auto is usually the better start.
Every Input, Gamma, and Output row on Master, Red, Green, and Blue resets before Auto writes, so a new result never stacks on an old one; the Alpha rows and Clamp Output stay as they are. The result is one undo step. When there is nothing to stretch, or Contrast and Color finds a color channel with almost no range (such as a picture with no blue in it), the panel says so and Auto changes nothing, or sets the contrast only.
For a correction that follows the image as it changes, use Auto Adjust, which runs the same methods live and gives the same values. To correct a cast by the color of the light, use White Balance.
32-bit values
Section titled “32-bit values”In a 32-bit document, turn off Clamp Output to carry brighter-than-white values through. Dragging Output White above 1.0 turns it off for you.
A 32-bit input keeps its full range even in an 8-bit project: Input Black, Input White, and Output White accept values above 1, Auto and Normalize read the true range, and Clamp Output appears, just as in a 32-bit project.
Picking a Black or White Point
Section titled “Picking a Black or White Point”Every channel has an eyedropper beside Input Black and Input White. Click one, then click the image in the Preview: the point is set to the exact value under the cursor, read from the image Levels receives before any display transform, so a scene-linear value or a depth distance of 7.2 comes back exactly. The cursor shows the value before you click, one pick is one undo step, and Esc or a right-click cancels.
- Master takes the darkest of the pixel’s red, green, and blue for a black point and the brightest for a white point, the rule Normalize uses, so the pixel’s color is kept.
- Alt-click on Master neutralizes: it sets the Red, Green, and Blue rows separately so the picked pixel lands exactly on black or white in every channel. On a white point, pick a surface that should be pure white; on a black point, one that should be pure black. Picking a gray would push it to white or black, not remove a cast; for that, use Contrast and Color.
- Red, Green, Blue, or Alpha takes that channel, allowing for whatever Master already does. A mask input takes its one value.
While the pick is armed, the Preview shows the output wired into Levels, even a second pin such as 3D Render’s Depth, with the upstream node’s own handles hidden. On a 32-bit picture it also turns on the Preview’s Normalize view until the pick ends, so the whole range is visible; the pick still reads the real value.
When a pick sets nothing (a transparent pixel, a value that is not a finite number, a value outside the row’s range, or a Preview showing a picture of a different size), the cursor says why and the pick stays armed.
An Inverted Input Range
Section titled “An Inverted Input Range”Input Black may sit above Input White. The mapping then runs backward, brightest input darkest, spread smoothly between the two points. Only when they are practically equal (less than 0.001 apart) does Levels switch to a hard cut.
Recipe: a height map from a depth pass.
- Wire 3D Render’s Depth output into Levels.
- Pick Input Black on the farthest part of the model (not the background) and Input White on the nearest.
Input White now holds the smaller value (a distance in a 32-bit document, an 8-bit code in an 8-bit one), which inverts the range so near is white and far is black; with Clamp Output on, the background beyond Input Black stays black. Auto and Normalize are the wrong tools here, because they map the background too and squeezes the model into a narrow band.
Texture sets
Section titled “Texture sets”On a texture set or a library, a Map row at the top of the panel picks the one map Levels edits, such as the Roughness, and every other map passes through untouched. The histogram, Auto, and Normalize read the chosen map, and on a one-channel map such as the Roughness the Channel row reads Master. The Input Black and Input White eyedroppers pick from that map too, in the set the Preview shows, never another map. On a Base Color map, Auto also sets the Output rows so the result stays between 30 and 240 (of 255), the range of real surface colors. See Changing one map.
Parameters
Section titled “Parameters”Pins
Color
Which map of the texture set this node edits. Every other map passes through unchanged. Shown while a texture set or a library is wired
Which channel to adjust
Master input shadow clipping point. Pixels at or below this become Output Black. The eyedropper picks it from the image
Master input highlight clipping point. Pixels at or above this become Output White. The eyedropper picks it from the image
Master midtone gamma
Master output shadow level. The darkest value after adjustment
Master output highlight level. The brightest value after adjustment
Red input shadow clipping point. Pixels at or below this become Output Black. The eyedropper picks it from the image
Red input highlight clipping point. Pixels at or above this become Output White. The eyedropper picks it from the image
Red midtone gamma
Red output shadow level. The darkest value after adjustment
Red output highlight level. The brightest value after adjustment
Green input shadow clipping point. Pixels at or below this become Output Black. The eyedropper picks it from the image
Green input highlight clipping point. Pixels at or above this become Output White. The eyedropper picks it from the image
Green midtone gamma
Green output shadow level. The darkest value after adjustment
Green output highlight level. The brightest value after adjustment
Blue input shadow clipping point. Pixels at or below this become Output Black. The eyedropper picks it from the image
Blue input highlight clipping point. Pixels at or above this become Output White. The eyedropper picks it from the image
Blue midtone gamma
Blue output shadow level. The darkest value after adjustment
Blue output highlight level. The brightest value after adjustment
Alpha black-point input. The eyedropper picks it from the image
Alpha white-point input. The eyedropper picks it from the image
Alpha midtone gamma
Alpha output black
Alpha output white
Limit the result to the Output Black to Output White range.
Turn it off to let values continue past the endpoints, preserving brighter-than-white detail through the adjustment.
Dragging Output White above 1.0 turns this off automatically.
Auto
How much of the darkest and lightest pixels Auto ignores, so a few stray pixels cannot set the range
Display
Render the histogram overlay above the sliders
Mask
How the connected color image is read as a mask
How the mask is sized when it doesn't match the image
Usage Tips
Section titled “Usage Tips”- Drag Input Black right to clip dark noise; drag Input White left to boost dim highlights. Or pick both points from the image with the eyedroppers.
- Raise Output Black above 0 to lift the shadows for a faded, matte look.
- Adjust single channels to correct a cast: lowering Input White on Red warms an image, and on Blue cools it.
- Connect a mask input to apply the tonal adjustment to only part of the image.