The Lyric S-Curve filter is an easily-controlled implementation of the classic S-Curve levels adjustment. It is used on low-dynamic range material to restore contrast to the mid-ranges. It effectively maps a narrow midtone range of input levels to a broad range of output values, using a transfer curve that is S-shaped. This can result in substantially more midtone detail on otherwise flat scenes, as in the examples above.
The Lyric S-Curve is produced by a Perlin Gain Function and is easily controlled by the single gain parameter. High gain values produce a more pronounced S-Curve and negative values produce an inverted S-Curve which compresses the midtones and stretches the highs and lows.
The Lyric S-Curve filter includes a set of effect controls that are common across all Lyric effect filters. For a detailed description of these controls, please see the Common Effect Controls documentation.
Additionally, all Lyric Effect filters can be applied through mattes or masks to constrain the filter effect to particular areas of the image. For background information on mattes and masks, please refer to the Lyric Matte Primer.
The single control for this filter is the Gain slider which controls the shape of the S-Curve. The example graphs below show the curve for several gain values.
This curve is used to control an adjustment of the source video image levels. If you consider the horizontal axis to be input levels from black on the left to white on the right, and the vertical to be output values, the curve defines how input levels map to output levels. A straight line maps ins to the same outs. The gain = 50 S-Curve maps the a large range of shadows to a small range of shadow on ouput, same for highlights, but a narrow midrange input is mapped to a broad output range, which causes the contrast stretch in the midranges.
The Effect Controls section is a set of common controls that are documented on the Common Effect Controls page. They can be used to achieve masked and other specialized filter effects.
Gain = -75
Gain = -50
Gain = 0
Gain = 50
Gain = 75