Setting Min Max Smoothing Range With The Histogram

Initial HDR ArcSinH stretched 3nm H-alpha image of M42.

Step 1

Hybrid ArcSinH stretched 3nm H-alpha image with its 8 bit histogram showing the default position of the red, green, and blue traingles or zoom position, min, and max range values, respectively.

Step 2

The green min value and blue max value for smoothing is set on the histogram then transferred to the Smoothing and Noise Reduction tool using the Set Min Max Apply buton.

Step 3

The feather range is set to 1739 and a soft 3x3 Gaussian smoothing function is applied to the image in the range [3048, 32259].

Step 4

The 10 bit histogram near the green min range value is combed. The green min range value could be set to 0 to make both the 8 and 10 bit histograms continuous in the dark background values. A 10 bit monitor would show the most gray levels when its 10 bit histogram is continuous.

Step 5

The histogram green min and max blue triangle positions are updated when the Smoothing and Noise Reduction filter is applied. The 10 bit histogram is now smooth and continuous near 0.

Step 6

Final background smoothed image with 8 bit histogram. The midtones and highlights can be sharpened and small dark dots in the left side of the image removed using the feathered midtone and highlight sharpening and clone tool example.

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