Two cameras on top of each other?

[Ajit Raj Prathi]

I recently came across a well known DP's story on Instagram in which it was seen two cameras were stacked on top of each other. It was noticable that both the cameras had different magnifications (different lenses). I can't help but wonder why he might have done this given that these cams shoot 4k/6k or so, he might as well have just cropped in as required. Would be great if someone with experience could explain why this is done. I have attached a screenshot for reference. 

[Phil Connolly]

Hmm an attempt to get more coverage?  Cropping reduces quality. Or they could have been running at different framerates, shutter speed, stills, VFX look around etc...

who could forget the 35mm/HD hybrid from:

 

[Malcolm Ian Vu]

Perhaps it's a stylized action shot.  The movie 300 used multiple cameras at different focal lengths on certain shots.  I believe they cropped the first, then blended to the second, cropped that, then blended to the third.  A highfalutin form of the "digital zoom" on cheap camcorders.

[Stuart Brereton]

I don’t know that they’re on top of each other for any reason other than just to get them very close together. This happens all the time when you have multiple cameras for coverage and you need to get them close to the actor’s eyelines.

[Christopher Santucci]

I was once asked by a motion graphics guy to place 2 cameras on same axis with different focal length lenses. 

I'm not sure if he ever made use of the both perspectives, however. It may have been just a safety measure.

[David Mullen ASC]

If you're doing a very symmetrical shot where you want the camera to be dead-center to a room but want a tighter b-camera angle too, sometimes you stack the cameras.  I did it for a scene where the main camera was low-angle over the shoulder of someone in a bathtub in the FG looking up at someone in the doorway, and the b-camera was tighter along the same eyeline but didn't have to be as low-angle, so the two cameras were almost over each other. Not quite because I didn't want to have to undersling the b-camera on a Lambda head, those are pain.

[Marque DeWinter]

We did this years ESPY awards promos this way and it was really about logistics.  Since his accident its very tough for Tracy to stand for very long and do lots of take etc.  We had a few dolly shots and needed a tight shot and a wider shot for the different cuts that were done for the different promos.  PLUS we were using a teleprompter (which had to be twice as wide).  So the setup allowed us to get both the wide and tight while having identical pushes (one dolly) and keeping a similar eyeliner and allowing talent to use the prompter.

 

Another consideration is I've had a few jobs with a similar setup where there is a wide more or less lock off type of shot that is on a wide with a large DOF so that the VFX people have plates that exceed the normal frame and then the main camera (which was the bottom one) change lenses to get whatever shot was needed for the project.