Bit depth
Mark Galer, Philip Andrews · 2004
Scanning and editing at bit depths exceeding 8 bits per channel Most scanners now in use scan with a bit depth of 32 bits or more. Although they are capable of discerning between more than 16.7 million colors (therefore increasing the color fi delity of the fi le) most only pass on 24 bits of the data collected to the editing software. Higher quality scanners are able to scan and export fi les at 16 bits per channel (48-bit). Some digital cameras are also able to export fi les in ‘RAW’ format in bit depths higher than 8 bits per channel. In Photoshop it is possible to edit an image using 16 bits per channel or 8 bits per channel. The fi le size of the 16-bit per channel image is double that of an 8-bit per channel fi le of the same pixel dimensions. Image editing in this mode is used by professionals for high quality retouching. When extensive tonal or color corrections are required it is recommended to work in 16 bits per channel whenever possible. It is, however, important to note that not all fi le formats support 16 bits per channel.