52 David Busch's Canon EOS Rebel T3i/600D Guide to Digital SLR Photography Going Topside The top surface of the Canon EOS Rebel T3i has a few frequently accessed controls of its own. The key controls, shown in Figure 3.11, are as follows: Mode Dial. Rotate this dial to switch among Basic Zone and Creative Zone modes. You'll find these modes and options described in more detail in Chapter 4. Sensor focal plane. Precision macro and scientific photography sometimes requires knowing exactly where the focal plane of the sensor is. The symbol on the top side of the camera, to the left of the viewfinder, marks that plane. Flash hot shoe. Slide an electronic flash into this mount when you need a more powerful speedlight. A dedicated flash unit, like those from Canon, can use the multiple contact points shown to communicate exposure, zoom setting, white bal- ance information, and other data between the flash and the camera. There's more on using electronic flash in Chapter 11. Figure 3.11 Shutter release DISP. button Main Dial Sensor plane Hot shoe Mode Dial On/Off switch ISO button