A lot of people ask why use a DSLR for high definition (HD) video not an HD Camcorder. There are various reasons and advantages of both but the use of Canon HD DSLR cameras by many professional filmmakers is a sign of how good they are and their benefits.
The first thing to remember in any comparison between DSLR and camcorder is that even if both are shooting at full HD 1080p (1980x1020) resolution then the sensors inside are still very different sizes.
In the same way that a mobile phone with 12Mp camera has nowhere near the quality of a 12Mp Canon 5D with the same number of pixels as the sensor inside is so much smaller, the camcorder also has a tiny sensor in comparison to the DSLR. The result is that the quality of the output from a DSLR video is so much better for low light work and for controlling the depth of field for video. The sensor in a camcorder has a surface area of approximately 4mm square but a full frame DSLR has a sensor size of 860 mm square.
1) Low light video shooting
If you imagine that light is a volume of water that is being captured and the sensor is a bucket then the camcorder would require at least 200 buckets to capture the same amount of light as the one bucket of the Canon 5D camera.
2) Depth of field
Due to the larger sensor size it means that the depth of field is much shallower and can be controlled unlike a camcorder where everything is in focus.
