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Using the Histogram and RGB Curves
The RGB curves are a visual representation of the image conversion LUT. The histogram shows the distribution of pixels in the image.
The RGB curves represent the mapping of the input data to the output data (in other words, the LUT content). For example, if you are converting a Cineon logarithmic image to a linear image, the input data is the logarithmic data and the output data is the linear data.
Adjusting Reference White and Reference Black
The point at which the curve reaches a value of 0 on the vertical axis is called the Reference Black. Any values in the image below the Reference Black value are mapped to black.
The point at which the curve reaches the maximum value on the vertical axis (for example, 255 for 8-bit or 4095 for 12-bit) is called the Reference White. Any values in the image above the Reference White value are mapped to white.
Adjusting the RGB SoftClip values
Once you set the Reference White value, you can soften the shoulder of the conversion curve by adjusting the RGB SoftClip value for any or all the RGB channels. When you soften the shoulder of the conversion curve, you soften the transition of colors toward Reference White.
To adjust the RGB SoftClip values:
- To modify all channels at the same time, enable the Lock button.
- Change the RGB SoftClip value you want to modify.
The shoulder of the selected R, G, or B curve changes dynamically.
Adjusting the Film Gamma
The Gamma of a typical film negative is 0.6. You may want to adjust the Film Gamma. For example, if you know that the negative was developed to a Gamma other than 0.6 or if you want the film to look like it was push processed when it was not, you may want to set the Film Gamma to a value other than 0.6.
If you want to use a different Film Gamma, enter the new value in the Film Gamma field. (usually rgb are locked for this?)
If you find that you must increase the Film Gamma to between 1.1 and 1.3 to be satisfied with your result, you may be compensating for the gamma of your monitor during the conversion. To avoid such compensation during the conversion, you need to calibrate the monitor and set the normal gamma corrections.
Adjusting Highlights, Gamma Correction, and Shadows
Adjust the brightness (luma) of selected areas of the image by modifying the Shadow, Gamma Correction, and Highlight parameters.
To adjust Highlights, Gamma Correction, and Shadows:
- To modify all channels at the same time, enable the Lock button.
- Change the Highlight, Gamma Correction, or Shadow value you want to modify.
You can adjust most of the LUT parameters directly on the curve using the gadgets. See Using the LUT Graph.
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