I'm pretty excited by the new Red Scarlet, but one point seems very limiting about its (high-)framerate capacity:
It's actually cropping the image on the frame when shooting at framerates higher than 30fps (see its tech specs
This of course will reduce the resolution, but that's acceptable. Even the Vision Research Phantoms do so - yes, starting with extremly higher resolution/framerate ratios of course!
The problem is that cropping means that if you have to match another scene angle of view you'll have to move your camera and/or change lens.
The "usefull" motion modes on the Scarlet are 4K and 3K. 5K at 12fps max is for timelapse and stills. 4K uses less of the sensor, making your lenses, "longer." The ratio goes from 1.3 to 1.6. A 30mm lens goes from, effectively a 39mm to a 48mm.
But a lot of us want to use 3K to get raw capture without huge files. 3K captures a 4.97MP frame using 36% of the 5K sensor area. The file size will be 56% the size of 4K.
However, the increasing crop factor makes a 35mm lens into a 70mm. So we are looking at options.
We need to know if S-16 glass is an option here. Some say it is. Some say some of it is, but not all.
I'd like to underline that 4K is the highest available resolution for video. It might be also important to point out that the there is also a limitation in the extremely useful HDR-X as well explained on this phil bloom post. It's okay, I think I can live without it if I get a good camera for a decent price.
What I'd like somebody to shed a light about is to: clarify what lenses would reasonably work for high framerate modes, and what should be done to ensure normal speed vs. high speed shots for the same scene will edit nicely together..
Also would be nice to have a real hands-on in the answer not only theoretical, about quality of the cropped videos and practical issues with the cropping factor, but it's not mandatory!