Compress Captured Images will cause all FITS format images taken with the Camera Control window to be saved using the proprietary compression mode. This is very helpful when using large format cameras, but the resulting FITS images cannot be loaded by other applications unless they are first uncompressed using MaxIm DL. (Batch Conversion is useful for this purpose.) The compression format is lossless, and a 3:1 compression ratio is common for typical astronomical images.

Save Data in Unsigned Format will cause 16-bit integers to be written to FITS files as unsigned numbers. Normally BZERO and BSCALE are written to the file to offset the data values.

When opening 16-bit images with negative numbers can be selected to Treat data as unsigned or Add offset to make positive. It is common for astronomical software packages to save 16-bit numbers as unsigned even though this violates the FITS standard; the first option automatically detects this situation and adjusts the image when it is loaded. The second option is used when images really do have negative pixel values. MaxIm DL cannot process such images directly; this option adds a pedestal to force the image to be positive. The value of the pedestal is added to the FITS header.

The Default File Extensions list is used to specify the file extension used by preference for each type of image file that MaxIm DL can read and write, and the format it proposes by default when saving an image captured by the camera. Scroll to the file Type you want to change, click on the entry in the Ext... column, and type the new default. When you select the Save or Save As commands, this extension will be "suggested" automatically by being appended to the filename. It will also appear in the list of extensions used to filter the files displayed by Open and other commands that read image files. Note that setting a non-standard file extension for a particular type does not preclude explicitly specifying either the usual or an arbitrary one. To reset an extension to MaxIm DL's original default, click on it, press Delete and then Enter.

File types with a checkbox in the column labelled with an asterisk can be selected as MaxIm DL's default save format. Check the format you prefer. For astronomical images, FITS is recommended.

Location of Temporary Files can be used to set the temporary file location used by MaxIm DL. Temporary files are used during median combine operations, maximum entropy deconvolution and when swapping out image buffers to reduce memory consumption.