[toni-a]

Folks those look like large format lenses.
Equivalent focal length for 200mm 8X10  is 28mm full frame , so this lens has a field of view of a 28mm on 6D, BC who loves equivalences will calculate for us the equivalent aperture on
A guy even manged to capture video with such lenses
https://fiddleoak.wordpress.com/2017/12/...mat-video/
https://petapixel.com/2017/12/30/guy-mad...eo-camera/

They are not lenses made for large format plate cameras, but for machines. 

If you consider that for photocopy duty they should cover at least A4 format, it is not equivalent to 28mm, but rather 24mm.
Quick math:
A4 -> 21 x 29.7cm. Lets take 30cm width.
135 format -> 36mm width.
Focal length 200mm.
300 / 36 = 8.33333333
200 / 8.3333333 = 24mm 135 format equivalent.
Aperture = 200 / 5.6 = 35.7mm
24 / 35.7 = f0.67 135 format equivalent.

My 400mm f4 lens would be a 50mm f0.5 FF equivalent lens when used on the same A4 format.

Thanks for the video. The guy videos the projection with a "normal" camera, rather than shooting large format video. Neat solution, though.

If they can make a pancake 20-40f4 full frame why they wouldn't do a pancake 18-45f3.5-5.6 APS-C??
Although I hate it but I had to buy again Sony 16-50 collapsible , a 18-45 pancake would be more than welcome otherwise 20-40f4 is a way better choice

A 20-40 f4 FF has nothing in common with a 18-45 f3.5-5.6 APS-C (Canon).
In Canon APS-C land, the equivalent to a 20-40 f4 FF would be a: 12.5-25 f2.5

yes but when you use the 20-40 and the 18-45 both on APS-C they should have close coverage and speed