The 400D uses the DIGIC II image processor, as is used in the 350D. The 400D file numbering system holds 9,999 pictures, as opposed to 100 photos in one folder with the 350D.
The 400D utilizes the DIGIC II image processor, identical to that used in the 350D. The 400D's file numbering system can store up to 9,999 images per folder, unlike the 350D which only allows for 100 photos within a single folder.