Levels Tool
-
Menu -> Image -> Levels
-
Levels tool
-
The Level tool provides features similar to the Histogram tool but
can also change the intensity range of the active layer or the image
background.
-
-
Modify Levels for Channel
-
You can select the specific channel which will be modified by the
tool: Value makes changes to the luminosity of all pixels in the
image. Color channels allow to change saturation.
-
Reset channel button cancels changes to the selected channel.
-
-
Linear and Logarithmic buttons
-
These buttons allow to choose the Linear or Logarithmic type of the
histogram.
-
-
Input Levels
-
The main area is a graphic representation of image dark, mid and
light tones content (the Histogram). 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.
-
A well balanced image is an image with levels (tones) distributed
all over the whole range. An image with a blue predominant color,
for example, will produce a histogram shifted to the left in Green
and Red channels, signified by green and red lacking on highlights.
-
-
Level ranges can be modified in two ways:
Three triangles as sliders: one black for dark tones, one grey for
midtones (often called Gamma value), one white for light tones.-
Three input boxes to enter values directly.
-
Output Levels
-
Output Levels allows manual selection of a constrained output level
range. There are also arrow-heads located here that can be used to
interactively change the Output Levels.
-
-
Reset All
-
This button deletes all changes made to the all channels.
-
-
Auto
-
Performs an automatic setting of the levels for all channels.
-
-
Three eyedroppers
-
These three controls determine three points on the grayscale. Any
level below the "Black Point" is black; any point above
the "White Point" is white. The "Gray Point",
which must be between the other two, determines the middle level of
Gray. All shades of gray are calculated from these three levels.
Only the image background is changed.
-
-
-
Preview
-
The Preview check box makes all changes to the levels dynamically so
that the new level settings can be viewed straight away.
-
-
Open
-
This button allows you to select a file holding level settings.
-
-
Save
-
Allows you to save any levels settings you have set to a file that
can be loaded later.
-
-