Many cameras have physical flaws which prevent individual pixels, columns or rows of pixels from responding properly to incoming light. The result is that portions of the image are at either the saturation level or the bias level, regardless of the amount of light that they've received. This command ameliorates the effects of these bad pixels, whether individual, or arranged in groups, columns or rows.
Availability of this feature depends on Product Level.
Twenty Bad Pixel Maps are available to accomodate different cameras, binning settings, etc. Select the one you want to use in the Bad Pixel Map drop-down. You can rename a map simply by typing the new name in the Bad Pixel Map field.
The table lists the bad pixels, rows, and columns. The Mode shows whether it is a column, row, or point defect. The X and Y coordinates give the location of the defect. Begin and End indicate the starting and ending positions for a partial row or column.
Bad pixel maps can be generated automatically, manually using the mouse, or manually using the keyboard (see below).
Two Correction Mode options are available. In Interpolate mode, bad pixels within the image are replaced by interpolating from surrounding good pixels. A small amount of Gaussian noise can be added to the interpolated values to improve the cosmetic appearance (only bad pixels are affected). The standard deviation of the noise can be entered using the Noise field. The image is trimmed if a bad column or row is at the edge of the image.
In Zero Pixels mode the pixel is simply replaced with a zero value. This is used in conjunction with dithering (moving the camera slightly between each exposure) and the Stack command Combine Tab Ignore Black Pixels option. By doing this bad pixels are simply ignored in the stacking process, resulting in a much cleaner final result.
Clicking the Save Map button will save the current map and close the dialog without processing the image. Process will save the current map, process the current image, and close the dialog. The Cancel button will close the dialog without saving.
Automatic Map Generation
Clicking the Auto Generate button will bring up the Auto Generate sub-dialog.
All pixels which have a value below the Dead Pixel Threshold will be marked as bad. All pixels which have values above the Hot Pixel Threshold will also be labeled as bad.
One method for generating the map is to take a flat-field exposure (evenly illuminated source) and knock out all pixels which are much above or below the average. To eliminate hot pixels, it is often better to take a dark frame and eliminate all pixels above a threshold.
Mouse Map Generation
Turn on the Use Mouse check box, and select the Mode as follows:
Point – click on a single pixel to mark as bad
Row – click anywhere on a row to set
Column – click anywhere on a column to set
Partial Row – click and drag to select a portion of a row
Partial Column – click and drag to select a portion of a column
The selected region will be added to the table automatically.
Keyboard Map Generation
This works the same as Mouse Map Generation except that the coordinates are entered manually using the X, Y, Begin, and End edit boxes. When the correct values are entered, click the Add button to add it to the table.
Entries can also be deleted or modified. First select the desired entry in the table by clicking on the item in the leftmost column of the row (Mode column). If you wish to modify the entry, change the appropriate edit field and click Modify. If you wish to delete the entry, click the Delete button.