Sunday, December 6, 2009

Canon 7D Video Analysis

I recently bought a Canon 7D.
For photographing it seems to be a wonderful camera. The auto focus works fine, and there is a ton of features that I'm sure will be very useful.

What is the purpose of this analysis?
- To find out strength and weaknesses of the 7D for filming. I'm focusing mostly on the negative sides since there is very little information about this on the net but tons of talk about how amazing videos it can create.
- make sure that people who consider using a 7D for video knows about the limitations.
- Illustrate problems so that Canon can find technical solutions to these problems.
- Find alternative cameras for filming.

Please do remember I love Canon cameras, but I do wish that the filming would be a bit more solid.

One of my main reasons for buying the 7D was to use it for filming nature films. Filming with an SLR compared to a camcorders have many benefits:
- short depth of field if you wish
- plenty of lenses to pick from. Zoom lenses, 50mm 1.4 etc.
- very high bitrate, almost 50Mbit.
- filters can be easily reused
- you can use it for both photos and filming.
- 1080p, 720 60fps slow motion.
- high quality images. Or is it? That is what we will look at.

Full Resolution
There are many videos on the net which shows videos filmed with 5D and 7D in very high quality. However almost all of these are shown in medium resolution like 800x600. What do these movies really look like in 100% resolution 1920x1080, 1280x720.

While filming with 500D I found many problems with the quality. Some of the problems are:
- extreme chromatic abberation. This means that there are very strong color shifts around contrast areas such as trees.
- alias. Jaggy corners and details.
- blurriness. The details are simply lacking.
- the camera is not so great as you would think in low light but feature strong noise.

High ISO
The image below shows ISO 3200 in a out of focus area. As you can see the noise is very strong, making it nearly useless.

ISO 100, 100mm 2.8 Macro at at f/6.
This lens is extremely sharp so the image should be as perfect as it can be.
The image illustrates that the details are blurry, there is chromatic abberation and in areas like the ceilings there simply isn't much detail.

1280x720. 60fps. Pretty high ISO (1000-2000 I think).
This images looks good. No problems here. Sometimes the films look fine and sometimes they look very weak. Not sure why, but it seems to have to do with contrast, light and patterns.
Market Details
1280x720 60fps can be nearly useless at times.
This market image has extreme aliasing, sometimes the pixels are double making a very chunky feel. Lines can also have a strong stair pattern. The details on the ground were also very weak and tiny stones kept popping in and out of the image.

Market Full Image
This is the full image of the market. 17-85IS. ISO is auto so it's pretty high. The lens may not be L quality but surely it should be good enough for shooting a scene in daylight without extreme alias artifacts.

As a summary the 720p 60fps creates often very weak material.
1080p is better but also has problems with detail.

What is the source of these problems?
The sensor of 7D has 18Mpixels, while the movie has only about 2Mpixels. The way the cpu deals with this is that it simply skips a lot of the lines or pixels in the sensor. So many pixels are not used, this will cause the jaggy lines and general lack of detail.

This was the first days testing of the Canon 7D. I hope to do more tests in the following week.