FAX files supports two standard resolutions:
High quality images look fine for displaying without resizing or zooming. This is the mode used when the "High quality mode" is used on the fax machines.
Standard quality images will look squished when displaying without resizing or zooming. In order to view the image properly, resize the image to expand the image's height twice. This is the mode used "High quality mode", is not selected. When a fax machine receives such images, they automatically double the height of the faxed image.
Fax machines support the standard quality mode to reduce the time required to fax something in half. When the image's height is reduced to half, the required transmission time is reduced to half as well.