Re: video camera best choices

I think you're looking at a lot of cameras that are very different. If having shallow focus is a priority, a camera like the Sony F-800 has a smaller sensor and therefore isn't as good for that. It would be a better camera for instances where shallow focus is a problem, not a good thing.

The RED popular because it has a 35mm sized sensor so you get shallow focus, and gives you enough resolution for TV and film prints. And it's cheaper than competing cameras, so lots of projects have started using it.

The Alexa is expensive because it also has a 35mm sized sensor, and it gives you enough resolution for TV and film prints. But compared to the RED, it does higher-quality image processing in the camera, is more light-sensitive, has other good professional features.

Digital SLRs have the 35mm sized sensor, but are usually thought to have too much compression and visual artifacts for TV and film work, and not much exposure range. A lot of the data that the sensor is capable of is compressed because the camera doesn't process and write the data quickly enough. That said, people have succeeded in using them in feature films and high-budget TV shows.

You just have to balance price vs. quality, and really know what the issues are with each camera to shoot them best.