One might assume that a lens is a lens and you can simply adapt any lens to suit ones needs. This is usually a matter of changing or adapting the mount just so the square peg fits in the square hole. The fact is that still lenses and cine lenses are very different and can’t always be interchangeable. Still lenses are defined (in my opinion) as lenses that were designed and built for use with an SLR still camera whereas a cine lens would be one designed and built for use on a motion picture (movie) camera. I’ll go over why the two aren’t interchangeable and what can be done to reduce the differences between the two. Modern still lenses are designed for two things… Speed and ease of use.
Manufacturers are always looking for a way to make the auto focus faster and simpler and over the past several decades this has been accomplished by making the focus components lighter and looser in order to make actuations easier for the tiny motors found in the lens or camera. The often plastic mechanics move in very loose, dry, and all together sloppy methods. The same can go for the zoom mechanics in a still zoom lens. This isn’t an attempt to make it easy for a motor, but just a fact of mass production at low cost. This isn’t a bad thing for a photographer taking still photos since the camera focuses nice and quick and then stops all adjustments when the photo is snapped at a fraction of a second. Another issue is that many new still lenses are abandoning manual aperture control rings for several reasons. The camera can control the aperture with no problem and it makes manufacturing cheaper. Lastly, still lenses continue to use focus distance marks, for the most part. But still lenses aren’t calibrated very well and the marks are often just a general guess rather than a reliable reference. Again, not a big deal if you are just depressing the shutter half-way to activate autofocus that doesn’t care what the distance is. All of these “issues” are only issues if you attempt to use still lenses to record motion. With the loose, easy mechanics, the image rendered by the lens on the film plane will jump around and jiggle if you try to adjust focus or zoom while recording. Nothing takes you out of a piece of art more than a jolt of motion similar to that of my moms video tapes of my school parade from 1990. Then there is the zoom. If you try to zoom or out while recording, forget it. Because still lenses aren’t calibrated and don’t hold focus, your picture will go from tac sharp to mush in a few millimeters. The lack of an aperture ring can be neglected since it’s still adjustable in the camera, but not always adjustable while recording. And even when a nice camera allows aperture adjustment while recording, you’re looking at adjustments in half or third stop increments that will simulate the exposure compensation that my phone exhibits.. Not pretty. There are a few other snags with still lenses that can be circumvented. The difference in standards is small, but detrimental. Still lenses don’t utilize external gears for use with a follow focus. Many people have turned to aftermarket add-on gears that simulate a focus or zoom gear. These can be garbage… Some of them use a block or clamp that interrupts the rotation and limits the user to a certain range.
That just about sums up a majority of the modern still lenses for motion use but alas, there are a few remaining still lenses that are fairly well suited for motion. The first that comes to mind is the Zeiss ZF series lenses. They are completely manual lenses that feature a nice, solid metal construction that eliminates the common image shift and focus loss. And then there are older manual lenses from back when auto-focus was just a myth. But those are hard to find in good condition. That’s about as close you can get to a cine lens with a still lens.
The major aspects that make cine lenses more expensive and higher quality are things like build faulty and materials. The tolerances used for designing and making a cine lens are much tighter than a still lens. The components in a cine lens are almost always metals and alloys. The mechanical designs have become extremely complex to avoid the dreaded image shift and to maintain proper calibration even with the severe abuse of modern Hollywood users. For example, a cine zoom will be a para-focal lens (maintains focus throughout zoom range) whereas still lenses can be vari-focal since you just refocus and snap the photo. This is important with a cine lens because the distances referenced on the focus scale are critical to the cinematographer and/or focus puller. These marks must be dead on every time or someone is going to have a heck of a time doing their job.
Cine lenses also take “breathing” into consideration. Breathing is a characteristic exhibited by a lens while focusing. The image will appear to zoom in and out very slightly, but enough to distract a viewer. Again, still lenses will do this a lot because you don’t focus the lens while the mirror is up and the shutter is open. A lot of the unwanted characteristics that come with still lenses can be overcome for use with motion picture. However, not always economical and usually mickey-moused… Obviously the more expensive, higher quality still lenses will have these flaws reduced and could very well be used with minor restrictions. But if you want to shoot motion pictures, you need motion picture lenses. So go ahead shoot your 5D MkII with the kit lens but don’t expect to produce anything on par with that of material shot with proper gear.