The File Type Options dialog is entered when you press Options in the Image Conversion dialog or the Send Image dialog. The dialog allows you to specify convert options for the currently selected image file format.
The available options depend on the file format. Here are shown the options for the JP2 file format.
Color Mode
Reversible
JPEG 2000 is based on wavelet compression. Images can be compressed in reversible mode which is a lossless compression. When the image is decompressed you get an exact copy of the original image. You can expect to achieve compression rates between 1:5 and 1:2 in this mode.
Otherwise, the original image cannot be reconstructed exactly during decompression, but the compression method strives to avoid visible artifacts. When you disable Reversible you can specify a target compression rate between 1:1 and 1:100 (se below).
Target Rate
Select a number or use the slider to specify a target compression rate between 1:1 and 1:100.
1:1 gives almost the same result as Reversible compression. When the slider is dragged to the right the compression is improved, but some details are lost. If you choose 1:100 you can save an RGB image of, say 1600x1200 pixels, in only 56 K bytes (the uncompressed image takes 5.6 MB), and the visible quality loss will be unimportant for many purposes.