Whew! This took some digging but I found it on another forum and thought it would be worth posting here:
8300 Picture Format Summary:
Fixed - Displays all content at whatever resolution you selected, based on what you selected in the wizard. You force the output to a single output and the box scales to that input. Easily changed in the settings menu of the box.
Pass Through - Passes the input signal through to the output with no change, unless you disable certain resolutions. For example 480i in to 480i out, 480P in to 480P out, 1080i in to 1080i out, 720P in to 720P out. If you disable 720P, 720P in will go to 1080i out.
Auto HDMI/DVI - If you are using the HDMI port, you will see this option instead of the Pass Through option. Resolution is automatically formatted to the scan rate supported by the TV.
UpConvert 1 - All 480i and 480P signals get upconverted to 480P. All 720P and 1080i signals get upconverted to 1080i.
UpConvert 2 - All 480i and 480P signals get upconverted to 480P. All 720P and 1080i signals get converted to 720P