Don Kotlos

In the test that you posted, the differences that you see in perspective are because of the different distances of the camera to the face. The focal length just changes the FoV. So in order to keep the same DoF you have to move the camera at different distances, which gives rise to different perspective. If you changed the sensor size in order to match the FoV, you wouldn't have to move the camera and thus the perspective would not be different. 
For example were you to have a camera with a very high resolution so you can crop, you could use a wide angle lens from far away and it could give you the same compression as the 300mm. 

I don't find it that great.
First of all because especially cinematographers need to know and adjust the DoF, FoV and perspective. That means then need to know the equivalent focal length for all different cameras with different sensor sizes. If you had a m4/3 camera with the 25mm @f/1.4 and you wanted to match the image with a FF camera then you would have to use a 50mm @f/2.8. You then use ISO/NDs/Lights to control exposure. 
 Second is because he was ad nauseam saying you cannot get the same look from different sensor sizes no matter what, even when people provided him with proof. He then he made a youtube video twisting the argument and saying exposure is everything. 
Lets not go back to that bitterness. 
Hopefully this is the last thread about it but lets say it one more time: Perspective only depends on the distance from the lens. You can then adjust the focal length/aperture for a given sensor size to get a specific FoV and DoF. 

There are some machine vision C-mount lenses that do resolve 4K but they are fairly expensive and certainly not worth buying for the M50. 
That being said, even if a lens does not resolve the 4K resolution, it can still create a very nice filmic image since you won't notice any aliasing artifacts and there is going to be a gradual decrease in amplitude of the higher spatial frequencies.  
 

@blondini No, perspective distortion is only affected by distance from the camera to the subject. No matter what sensor/lens combination you use, if the camera and the subjects don't move, then the ratio of the size of two subjects will remain the same. I did a quick and dirty test to illustrate. It's a little imprecise (the camcorder would NOT focus on the guy in front...)
For all three images the camera is in the same place. I suspect the small discrepancies in ratio (2.2% error) are mainly due to moving parts inside the camcorder when it zooms, which changes its actual distance from the subject. But this is an easy thing to test yourself.
First image is a 4mm lens on a 1/4 type sensor

Second image is a 55mm lens on an APS-C sensor

As you can see, the ratio of the figures is the same. You could even use a wider lens and the ratio remains, because the distance has not changed:
Third image is a 2mm lens on the 1/4 type sensor.

 
Quote from Wikipedia:
 
 
 
Yes, it would. As long as the camera is in the same place, the relative size of the plane compared to the people will remain the same regardless of the lens or sensor. If you don't believe me or my Legos, go try it yourself!

That depends.     The lenses have to be considered with the camera used.
In any case, I think I much prefer the (cheaper) Sony Zeiss 55 1.8 to the Olympus 25 1.2. (yes it is not 50 but it is close enough).
I have had a LOT of normal lenses including a Canon FD 50 1.2 I loved and Pentax 50 1.2 that I loved to death (it eventually fell apart on me) but the Sony Zeiss has cured me of all of those others.
I also think the FE 85 1.8 is the biggest bargain going in photography for any brand and used on a FF camera I would also prefer it to the Fuji 56 1.2  and the FE 85 is also cheaper than the Fuji.      The FE 85 IS an absolute bargain but it is also an excellent lens and has similarly cured me of all the other 85s I have had (still have an FD 85 1.2 L).
Just my opinion.
EDIT and a couple of other reasons they are even bigger bargains.
Both those lenses (55 1.8 and 85 1.8) can be used as 2x virtually lossless zooms in video (as any other lens can and also for Jpeg stills) and also be used both FF and APSC on the FF Sony E mount cameras.

Cheers Don. Understanding equivalence was a super useful, practical insight for me. So if a thread keeps a constructive and inquisitive tone, I am glad to see people explaining and listening to each other

I don't find it that great.
First of all because especially cinematographers need to know and adjust the DoF, FoV and perspective. That means then need to know the equivalent focal length for all different cameras with different sensor sizes. If you had a m4/3 camera with the 25mm @f/1.4 and you wanted to match the image with a FF camera then you would have to use a 50mm @f/2.8. You then use ISO/NDs/Lights to control exposure. 
 Second is because he was ad nauseam saying you cannot get the same look from different sensor sizes no matter what, even when people provided him with proof. He then he made a youtube video twisting the argument and saying exposure is everything. 
Lets not go back to that bitterness. 
Hopefully this is the last thread about it but lets say it one more time: Perspective only depends on the distance from the lens. You can then adjust the focal length/aperture for a given sensor size to get a specific FoV and DoF. 

I don't disagree with the fact that smaller sensors require far better glass in order to get similar performance to larger sensors. 
But the differences that are visible in that test are mostly due to perspective and not distortion, which is really a problem when shooting architecture (both stills & video). 
In any case, I believe the m4/3 still has its place. Small cameras such as the E-M5ii or the PenF coupled with tiny lenses such as the 17/1.8 and 45/1.8 are a joy to carry around your neck and shoot all day long. Something that even the A7rIII & the 35/2.8 cannot really achieve. If on the other hand you are after image quality or shallow DoF, then instead of start buying expensive & large glass for m4/3, my opinion is that a FF camera will offer a much better solution for the same price/size/weight. 
Thats why I wish Olympus & Panasonic really put an effort to keep their systems small enough but pleasurable to shoot with. For example I would really love a PenF or a GX9 with a state of the art HUGE EVF that I would want to use instead of using subpar components like the GX9 did in order to save costs  ( I would also remove at least half the buttons from these cameras  ). 

Just saw it, and was thinking about you and your mic placements, @IronFilm.

I feel quite the opposite. While i like the manual dedicated dials for photography, for video it is a pain. The shutter dial especially is not that useful since you have to use two separate dials to get my most used speed 1/50. I shoot mostly in manual mode with autoISO and I frequently adjust the shutter speed between 1/25 and 1/100.  And for the ISO dial you rarely need to select one specific ISO value. It is mostly adjusting for exposure or setting it to auto. 
For video I much prefer the dumb assignable dials. Easier to quickly set a value with just one finger. I have set the back control wheel to change the ISO which also has an auto position. Moreover, I wish every company implements the smooth auto ISO of the Sonys. The exposure changes as smooth as the variable electronic ND of the FS5. 
 

Yep, perspective is only affected by the distance of the objects to the lens. The focal length & sensor size do not affect perspective in any way. A 25mm on a m4/3 sensor with an aperture of f/1.4 will have the same perspective and DoF as the 50mm on a FF sensor with an aperture of f/2.8. The other aspects of the image like distortion or busyness of the bokeh depend on the design of the lens and not the focal length/aperture/sensor size. 

Companies would love it if everyone believed this , but unfortunately (or fortunately for our wallet) it is not the case.
I have built and bought too many computers over the years.  Currently I am using a MacPro from 2010 with 12 cores, 64gb ram, an M.2 NVMe boot drive and a Titan X GPU and I can tell you this is no way obsolete:
 
That was of course when Apple made computers for professionals  . But with windows, which have even more choices, you can easily update any part of the system. Even with different generation CPUs you just need to upgrade the CPU+motherboard. RAM technology does not change that fast and easily lasts for ~10years. 
Future-proofing is very important when building a computer. Unless someone has either too much cash to waste or no idea how to build a computer that is. 

Companies would love it if everyone believed this , but unfortunately (or fortunately for our wallet) it is not the case.
I have built and bought too many computers over the years.  Currently I am using a MacPro from 2010 with 12 cores, 64gb ram, an M.2 NVMe boot drive and a Titan X GPU and I can tell you this is no way obsolete:
 
That was of course when Apple made computers for professionals  . But with windows, which have even more choices, you can easily update any part of the system. Even with different generation CPUs you just need to upgrade the CPU+motherboard. RAM technology does not change that fast and easily lasts for ~10years. 
Future-proofing is very important when building a computer. Unless someone has either too much cash to waste or no idea how to build a computer that is. 

Yep, perspective is only affected by the distance of the objects to the lens. The focal length & sensor size do not affect perspective in any way. A 25mm on a m4/3 sensor with an aperture of f/1.4 will have the same perspective and DoF as the 50mm on a FF sensor with an aperture of f/2.8. The other aspects of the image like distortion or busyness of the bokeh depend on the design of the lens and not the focal length/aperture/sensor size. 

I use the c500 for all my work 2k 60 12bit the C300 mkii does not have this. It is an amazing camera. I think you can get DPAF on this it’s not been done however it is the same sensor as the C300 mk1 and that has DPAF.
Re: Pro Res Raw, in the menus it does have 4k 60 raw and 4k 120fps half raw email Atomos and shout about it they should consider it. 
Here is some of the Work shot with the c500, a documentary I am working as a DP on 
 
 

Forced AF with an AF-ON button does not work well in video mode. Gives too much hunting. 
So my practice is to have a dedicated button that toggles between AF/MF. When I want to focus I engage the toggle and to set the focus point you can touch the point on the touchscreen. Then turn off if you don't want to change focus any more. Woks reliably for me. 

I used the 25m T/0.95 from slrmagic extensively and enjoyed it a lot. The GH5 still lags behind though compared to full frame. You need the GH5s in order to much the low light performance for the same DoF (two stops slower on the FF) at least in video. For photos there is still at least a 2 stop difference between m4/3 and FF and will always be the case for sensors with similar technology and a 4 times area difference. 
The advantage of the FF lenses is that you can get very good AF with very shallow DoF which can also work great with video. The eye-AF is just an amazing thing to have if you like shooting faces with very shallow DoF.  
Another important point is that while these lenses are OK for video, the quality is not great for stills. You have to go up to the newer Olympus f/1.2 PRO line to get really good results, and then you are actually paying a lot of money for a m4/3 lens and still lag behind in the sensor department. 

Yep, perspective is only affected by the distance of the objects to the lens. The focal length & sensor size do not affect perspective in any way. A 25mm on a m4/3 sensor with an aperture of f/1.4 will have the same perspective and DoF as the 50mm on a FF sensor with an aperture of f/2.8. The other aspects of the image like distortion or busyness of the bokeh depend on the design of the lens and not the focal length/aperture/sensor size. 

Forced AF with an AF-ON button does not work well in video mode. Gives too much hunting. 
So my practice is to have a dedicated button that toggles between AF/MF. When I want to focus I engage the toggle and to set the focus point you can touch the point on the touchscreen. Then turn off if you don't want to change focus any more. Woks reliably for me. 

I used the 25m T/0.95 from slrmagic extensively and enjoyed it a lot. The GH5 still lags behind though compared to full frame. You need the GH5s in order to much the low light performance for the same DoF (two stops slower on the FF) at least in video. For photos there is still at least a 2 stop difference between m4/3 and FF and will always be the case for sensors with similar technology and a 4 times area difference. 
The advantage of the FF lenses is that you can get very good AF with very shallow DoF which can also work great with video. The eye-AF is just an amazing thing to have if you like shooting faces with very shallow DoF.  
Another important point is that while these lenses are OK for video, the quality is not great for stills. You have to go up to the newer Olympus f/1.2 PRO line to get really good results, and then you are actually paying a lot of money for a m4/3 lens and still lag behind in the sensor department. 

Canon 1DC is better than the M50 
 

I have mentioned that before, but I will do again here: When playing with picture profile settings it is important to change the exposure from -3 to +3 stops in order to observe any potential color shits. Some combinations produce more color shifts than others, so adjusting the exposure for skin is a good tactic in general. 

I know it is not a solution for everyone, but I use Lightroom to copy all my footage (stills/clips) and with the "rename during import" function you can adjust the naming as you wish. I use the date + sequential numbering. 

Watch the LS-300 get a Raw export. It would be the camera that just keeps on giving.

I've taken full advantage of its very flexible mount and had all sorts of lenses on it!
Angenieux B4 ENG Lens with 2x doubler (which the onboard prime zoom can double again), RED PRO PL zoom and primes, Nikons, Canons, Contax Zeiss, M42 Zeiss and Meyer Optik, Leica R and the most recent one is the Mamiya 645 Medium Format 35mm.
Oh and native m43 as well obviously!
The only bugbear is having to dismantle the feet off the Canon and Nikon speed boosters as they won't mount as the ND wheel protrudes ahead of the mount.
I'll do you a few frames of JLOG tomorrow if I get a chance so you can have a look. There is a freely available LUT from JVC that you can download as a starting point. There is also a Leeming LUT for it but obviously thats a paid option. 
Pick a lens if you want to kill 2 birds with one stone.