Crop mark at this resolution no data is lost and all of resolution is utilised from sensor to the max, we end up with 3.2k CINEMASCOPE at popular 2.39 ratio ready for the cinema , surely
it could be also crop mark add for 1816.78 x 1366 for 2.66 ratio as well.
Another benefit of having just a "
framing fake crop mark" is that we will still retain full horizontal resolution with 2X anamorphic lens which will end up like almost 5K allowing to horizontally
"pan" or create "dolly shots" like or reframe shots while still retaining true 3.2K resolution.
Creating custom crop marks for Magic Lantern is simple as creating them in photoshop and dropping files in software folder, as many as you like, even
there is tutorial so user can do this :
http://magiclantern.wikia.com/wiki/File:Cropmarks_TutorialSomething like this would be awesome , not to mention that with this workflow 3.2K would upscale to 4K with ease and here we go 13 stop DR RAW almost true 4K Cinemascope ready for IMAX from BMCC