Workflow and image/video formats for rendering high quality photos as animations? I want to preserve as best I can the quality of digital photos taken in RAW format and then rendered as animation sequences in Blender. My workflow is as follows:


Process RAW (.cr2) images with Darktable
Export as OpenEXR
Track and composite animation sequence in Blender
Save animation as OpenEXR image sequence
Open multiple image sequences in VSE and render final video file


The OpenEXR format is very large (over 200MB per image). Do I need to use it in both steps 2 and 4? Also, what settings should I use for the final video render?
It is more common to save the output of blender rendering as a set of PNGs.  You can turn up the compression in the Render > Output section, but I can not predict if it will save space compared to the OpenEXR.

Making a VSE output to compressed video (as you do) is very common, and almost required if there is any sound involved.  The settings you use for the final video render will vary depending on


how much bandwidth you are willing to allocate for streaming
resolution of video (3.75Mbit/s MPEG-2 is CableLabs VoD standard for SD.  You will want 4-9Mbit/s for H.264 1080p video)
what formats are supported by the client software (motorola DCT-2000 -vs- iPhone)
does the container support the codecs you want (MPEG-2 program stream doesn't support AAC and blender does not seem to support transport streams)


Some more reading is at http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Output/Video