There are four reasons why I strongly feel the MK series of lenses opens a door to a new era. The first one is that they bear optical performance and mechanical structure that satisfies the demanding cinema standard. The second one is that they have superior image quality to many prime lenses. The third one is how compact and lightweight they are. The forth is their unbelievable price.
Firstly I would like to mention "optical performance and mechanical structure that satisfies the demanding cinema standard".
FUJINON Cine Lens "MK50-135mm" new lineup for MK series
Features of FUJINON MK series - New MK50-135mm
One of the biggest differences between cinema and still lenses is the seamless iris. Most still lenses can only have their aperture value changed in 1/3 or 1/2 steps. The iris in cinema lenses can be changed linearly, giving maximum control to get the proper exposure. The MK series of lenses achieve T2.9 through the entire zoom range and their performance is superb - even at the widest aperture.
Decades of "FUJINON" technology is condensed into the MK series. Zoom lenses are much more difficult to design than primes - their performance has to be guaranteed at all zoom positions.
When using zoom lenses for still photography, the point of focus will shift while zooming, making it necessary to adjust the focus every time you change the zoom position. When it comes to shooting a movie, not only is it a requirement to focus check every single time the angle of view is changed, but scenes with any kind of zooming are unusable. This makes it a big burden, especially for documentary shooters.
The MK lenses are designed to suppress focus shift while zooming. Once a focus position is set, it will not shift even when the zoom position is changed. If you adjust the focus at the telephoto end, which is easier to see, you can then change the angle of view as you want and know that your focus point will not change at all.
Optical axis shift is literary the “shift” of the center position while zooming from wide to telephoto. The MK lenses are designed to suppress this completely, ensuring that no re-framing is required after the angle of view is changed, and movies with zoom scenes do not show any imperfections in framing.
Lens breathing, changes of the angle of view while focusing, occurs with almost all still lenses. While shooting a movie, the focus is often changed during a scene so breathing must be suppressed in order not to ruin it. Despite being zooms, the MK lenses suppress lens breathing incredibly well. This is due to the accurate lens design.
Despite weighing less than 1kg each and being very compact, the mechanical design of the MK series is completely to cinema specification, inherited from FUJINON’s PL mount HK, ZK and XK top cine lenses. By supporting the E mount, the MK lenses combine portability with high image quality, yet the operability is totally different from still lenses.
It is very easy to focus on subjects thanks to a 200° focus rotation angle. In most still lenses, the focus position angle is quite narrow making it is hard to focus on fine details. That's why some people rely on auto focus. The MK lenses are not only very accurate, but also have a great torque feeling.
The gear pitch for the iris, zoom, and focus rings are all 0.8M, allowing use of third-party cinema accessories. For still lenses, you often need to prepare other gear rings to attach follow-focus systems. Adding an additional gear ring causes focus operation to not be perfect since there is some clearance between the follow-focus and the ring. With the MK lenses, you're able to use cinema standard systems without any stress.
Despite the appearance of cinema lens and still lens being similar, their design concepts are completely different. There are so many additional performance functions needed in real movie shooting location. In such an environment, the MK lens series will open up a new digital cinema world.