This is a format that is used for RAW images on Nikon cameras. It contains metadata about the lenses that were used to take the photo, capture settings, and other conditions. It provides a record of the data array obtained by the camera sensors through the lens. It allows you to edit the sharpness, colors, and tones with no loss to the content or quality of the image, which is something that cannot be done with compressed images. It supports 12- and 14-bit images.
PBM is a Portable image in black and white. Can be opened with programs: Adobe Photoshop CS, ACD Systems Canvas 15, ACD Systems ACDSee 17, Newera Graphics Converter Pro, Corel PaintShop Pro X6. File contains 1 bit per pixel. PBM is a kind of file format PPM. And can be readable or binary.