Maximum Entropy


The Maximum Entropy Deconvolution method sharpens an image while reducing noise. Maximum entropy processing works best on images having high contrast and high signal to noise ratio. See this Example. The High Pass Filter runs faster but creates more noise for a given amount of sharpening.

Properties of Maximum Entropy Deconvolution

Initial FWHM

The Full Width at Half Maximum (FWHM) of the point spread function for the image, measured in pixels. This measures the amount of smearing in the image. It is important not to overestimate this value or this could lead to rings around point sources and edge ripples. The value should not be less than about 2.0.

Camera Noise

For a CCD camera, this is the Readout Noise. This quantity is measured in electrons (e). For example, if the readout noise is 9.2e-, enter 9.2.

Camera Gain

The ratio of output signal number to input electrons. This is a value like "2.8", meaning 2.8 electrons per Digital Number ("DN", also called "Count" or "ADU"). Electronically, this is actually the "inverse gain" but is referred to as the gain for a CCD camera.

Max Iterations

Specifies the maximum number of iterations of the deconvolution. Mira will stop early if no change is detected.

Use Cursor ROI

If checked, only the region inside the cursor is deconvolved. Otherwise, the entire image is processed.

Using Maximum Entropy Deconvolution

Maximum Entropy only works with intensity images. It does not work with RGB images. If you want to process an RGB image, you will need to extract the channels and process them separately. However, the dynamic range will be lower since each channel of the RGB image will have been reduced to 256 levels. For RGB images, it is best to perform Maximum Entropy processing on the intensity images before merging then into RGB form.

Tip

When MaxEnt processing is active, you can break out of the loop at any time using the [Esc] key.

Choosing Properties

For best results, the Properties must be chosen carefully. Mira's implementation of Maximum Entropy processing uses 3 Properties: FWHM, Camera Noise, and Camera Gain. The dialog shows two sets of Properties:

Values in the right column are shown simply as a guide in choosing the Properties that are used from the left column.

Related Topics

Spatial Filter Commands, Example of Maximum Entropy Processing, High Pass Filter