Although the rubber surround is slightly smaller than that found on the EOS 10D the actual eyepiece itself is only very slightly smaller. Just like other EOS SLR's the EOS 300D's rubber surround can be removed to allow the eyepiece to be covered using the supplied cover (to block stray light entering the camera in long exposures) or for the use of add-on finders. The viewfinder has dioptre adjustment via a small wheel at its top right corner.
One of the important differences between the EOS 300D and the EOS 10D is that the 300D now uses a 'pentamirror' viewfinder compared to the 10D's 'pentaprism'. The difference is that instead of a glass prism block in the viewfinder chamber a lightweight (and cheaper) set of mirrors achieves the same reflection of light from the shutter mirror to the viewfinder eyepiece. The primary disadvantage of a pentamirror is that there is slightly more light loss and so the viewfinder image will be slightly darker. That said we couldn't see a huge difference between the EOS 300D and the EOS 10D in this respect (the biggest difference will be from the maximum aperture of the lens used on the camera).
Note that the EOS 300D has no center metering circle indicated on the viewfinder focusing screen (primarily because you can no longer select the metering mode manually). Also note that unlike the EOS 10D the AF areas are indicated by a small LED dot in the center of the AF point rectangle rather than the entire rectangle glowing red. With a depression of the shutter release button (half or full) this dot will briefly light to indicated the selected AF point (either automatic or manual).
It's worth noting that the EOS 300D's mirror isn't as fast or as well damped as the EOS 10D, there is noticeably more 'mirror slap' (vibration through the camera body as the mirror flicks up) as well as a slightly longer viewfinder blackout time.
The EOS 300D's battery compartment is in the base of the hand grip behind a plastic door (with a metal hinge). The door can be removed to make way for the optional battery grip. The EOS 300D takes Canon's almost standard BP-511 or BP-512 Lithium-Ion battery pack (7.4V 1100mAh, 8.1 Wh). Note that there is also a small rubber cover on the inside edge of the hand grip where the cable from the optional A/C adapter dummy battery exits the battery compartment.
The EOS 300D has the exact same CB-5L single battery charger as supplied with the EOS 10D. The indicator light at the top of the charger blinks a number of times to indicate the current charge level. A full charge takes 90 minutes.
Battery Grip (optional)
The optional BG-E1 battery grip (the BG-ED3 is not compatible) attaches to the EOS 300D in the same way as the BG-ED3 did on the EOS 10D/D60/D30, that is you remove the battery compartment door, insert the grip into the battery compartment and tighten the tripod screw into the base of the camera. The BG-E1 provides two battery slots (for up two BP-511 batteries) as well as a vertical grip, shutter release, main dial, AE/FE lock button, AF point selector and exposure compensation button.
Compact Flash Compartment
The Compact Flash compartment on the EOS 300D is at the rear corner of the hand grip, the red CF activity light is at the bottom right corner of the four way controller. The door itself is plastic with a metal hinge, opened by pulling back and flipping open to the right. The EOS 300D is compatible with either Type I or Type II CompactFlash cards and supports the IBM Microdrive, it also supports the FAT32 filesystem which means you can use cards over 2 GB in capacity.
I'm stunned that Canon still haven't addressed the same serious flaw in the operation of the CF door which we first noticed on the EOS-D30 and has afflicted the EOS-D60, EOS 10D and now the EOS 300D. This is: as soon as you open the CF door the camera powers down. This means that if there are images still buffered to be written (such as a burst of images in drive mode) they will be lost as the write operation is immediately interrupted. A simple fix to this would to allow writing to continue but to have an alarm as implemented on the PowerShot G3, the camera completes its write operation but a loud continuous tone sounds if the door is opened. It's remarkable that Canon still haven't fixed this.
On the left side of the camera are all of the cameras connections, these are protected by a rubber cover, note that this is fits flush when closed (an improvement). In summary from top to bottom: USB (1.1), Video Out, Remote terminal (right; E3 type). Note that unlike the EOS 10D the EOS 300D does not have a PC Sync terminal (although you can still use studio lights with a cheap hot-shoe->PC Sync adapter). The EOS 300D now supports PictBridge direct camera to printer (via USB) printing.