PixInsight

Screen Transfer Function

updated: 2024-03-23


Purpose

´╗┐Defines a set of histogram transformations applied to the screen rendition of an image, without modifying its pixel data.

     

screen transfer function (STF) in PixInsight is used to improve the visibility of an image as it is represented on the screen, but without altering its pixel data in any way. This is useful to work with processes applied to linear, unstretched data. Such processes may include color calibration, deconvolution, wavelet transforms, and some noise reduction procedures, among many others. Unstretched raw images are often poorly represented on the screen. This is because most of their data are concentrated in small portions of the available dynamic range. This can be easily identified as a narrow peak near the left side of the histogram.

A STF is a histogram transformation that PixInsight applies to the bitmap generated to render an image on the screen. STF parameters include per-channel midtones balance, shadows and highlights clipping values, just as any histogram transformation does. STF includes also dynamic range expansion parameters, but these are only available through the command-line and scripting interfaces of the ScreenTransferFunction process, not on its graphical interface.

In PixInsight, each view can have its own STF, which can be adjusted independently for the red/gray, green and blue nominal channels, plus an additional luminance STF that applies only when the CIE L* and CIE Y* components are being rendered on the screen, in the corresponding display modes. This allows for very precise and fine-tuned adaptations of screen renditions to raw data. ScreenTransferFunction allows you to work with linear images, just as if they were nonlinear, in an easy and completely transparent way.

Activation

Menu: Process ­čí║ All Processes ­čí║ ScreenTransferFunction

Process Explorer: IntensityTransformations ­čí║ ScreenTransferFunction

Input

all images

Output

n.a.

Previous Step

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Next Step

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Tutorial

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