Scanners are broadly classified into Flat Bed and Sheet Fed. The former are mostly preferred taking comfort as the consideration but even the Sheet dess are largely available and mostly found in all in ones.

These mostly come with the USB port these thereby giving you easy plug and play operation. Optical Scanning Resolution is the most crucial thing when scanning , the more it is , better it is in terms of output but not in all cases. A high resolution should appropriate for an image but if you looking to print the documents, one with a lower optical scanning resolution should suffice. Also the resulting higher resolution images would actually result in higher file sizes which would not at all require.

Some come with the touch buttons for functions like scanning , emailing etc and others do not. If you are ok without it , its good but if you crave for them, then you should ensure they are held in the machine before you buy them.

Color depth is precisely the details that the machine would put into the resulting image. The Color depths are often noted as the 24 bit, 36 bit, 48 bit and so. This also play a role in the clariy of the resultant pictures. Higher color depth would certainly improve the quality but you might not want unless you are scanning images or so.