Canon 6D vs T3I

1. What is the difference between a Full Frame Camera and a Crop Sensor?

  The camera's sensor size is known as the "crop factor" or  "crop sensor", compared with a "full frame" that is a sensor of 24mm x 36mm. A full frame sensor has a better image quality, but they have a disadvantage in ISO performance than with a crop sensor.

2. What are five advantages of the 6D compared to a T3i?

• the 6D camera has a full-frame 
•  about 30% better image quality
• it can distinguish 1.7 more bits of color
• it's more comfortable to hold
• battery endurance 

3. What makes the autofocus of the Canon 5D Mark III better than that of the 6D? 

The Canon 5D Mark III has a 61 point AF and in comparison with a 6D that has an 11point AF with one across-type Af sensor in the center.

  Canon 5D

6D