As someone prone to discussing video gear with just about anyone willing to engage in related conversation, one topic that is frequently brought up to me is the price and purpose of professional video gear and the seeming price disparity, in contrast to consumer or prosumer gear. In this installment of pro gear discussions, I will delve into what separates professional cinema lenses from their prosumer and consumer ilk.
Questions that I used to get while I worked in equipment rentals would commonly include, “Why do these cinema lenses cost so much more than photography lenses? Are they so optically superior?” and, “Will I see an appreciable difference using cinema lens “x” as opposed to a similar photography lens?” The combination of the seeming democratization of resources that can realize cinematic results and the appearance of “budget” cinema-lens offerings on the market has only intensified this discussion. Further muddling the field, inexpensive optics once relegated to DLSR and mirrorless cameras have found their way into cinema-grade housings; starting with the Zeiss Compact Primes (based on Zeiss Classic optics for DSLRs), introduced circa 2009, followed by Canon, with its CN-E primes, in 2011, all the way to Rokinon’s XEEN range and Tokina’s Cinema ATX zoom offerings, which came to market in 2015.
To those who are unfamiliar with what constitutes a cinema lens, differentiation beyond the superficial appearance is not enough to warrant paying a significant premium. Although, if the price were truly unreasonable, no one would pay it, right? So, what would you be getting for your dough?
This is an easy one. Just by looking at a cinema lens, it’s easy to see the difference in contrast to a photography lens. On the outside, lenses designed for motion pictures are much more “industrial” and utilitarian in appearance (though some might suggest that there is a beauty in that utilitarianism). They have gearing on their adjustment rings, usually conforming to the cinema standard 0.8 MOD spacing for interfacing with follow focuses, and will occasionally have mounting points for additional accessories like lens supports or focus/zoom/iris motors. Within a set of lenses, the spacing of the drive gearing is generally consistent. This saves time when attaching and detaching the lens from the camera, because motors and other accessories don’t have to be repositioned. The mount on cinema lenses, most commonly an ARRI PL (Positive-Lock) mount, is usually manufactured from stainless steel or a similar hard metal for consistent flange-focal distance. Softer metals and plastics seen on photography lens mounts can introduce inconsistencies in flange-focal distance, possibly causing focus consistency issues.
The beauty of cinema lenses is not skin deep, though. The inner workings of these lenses might even be more intriguing than what’s on the outside (it is for me, at least). This area is where standard photography and true cinema lenses differ the most. Lens design is a compromise of physics, and different compromises are made for cinema lenses, as opposed to photography lenses. Photography lenses generally require autofocus, and employ focusing element groups that are lighter and smaller to facilitate quick autofocus operations. Cinema lenses, with very few exceptions, are built exclusively with mechanical focus, which is operated externally; either with your hand, a follow focus, or with lens-drive motors. Since no compromises must be made to enable autofocusing, the manual focus mechanisms inside cinema lenses can be manufactured with greater complexity and robustness, featuring more moving elements and greater precision, in general. These advantages ensure that image adjustments can be made as smoothly as possible.
One mechanism that many cinema-lens manufacturers employ in their focusing groups is the cam. Cam-actuated focus, in which one or more element groups is secured to the focusing ring via their own cam, can affect individual element groups during the focus rotation. In contrast, helicoid-based mechanisms, which use screw threads on the inside of the focusing ring, are easier to manufacture, require fewer moving parts, and provide a reliable lens at a lower cost, though they can’t affect multiple-element groups in different ways simultaneously—it’s an all-or-nothing operation. Another major advantage to cam-based focus mechanics is that the element actuation doesn’t have to be completely linear. Practically speaking, one part of the focus ring rotation can move the focus elements more, while other parts might move it less. This can give more rotation real-estate for distance markings in critical areas of the focus ring, for example, the areas closer to infinity focus.
Despite their complexity, cinema lenses are designed to be serviceable on multiple levels. If you have the requisite equipment and experience, many aspects of the lenses are user serviceable. Lens mounts on many new lenses are interchangeable, and with Angenieux’s EZ line, rear optical blocks are also swappable. The Zeiss CP.2 line was the first to introduce user-swappable mounts, a feature passed down to the CP.3 primes, and now XEEN, Tokina, Schneider, Angenieux, and even Cooke are following suit. More advanced operations, like optical re-centering, collimation, and element swapping can be taken care of by your local lens technician. The mechanical nature of these lenses means that trained professionals will likely be able to service most issues that might arise from daily use without shipping them back to the manufacturer.
Advanced Optical Design
Computer-aided design has led to much of the recent innovation that’s been happening in the world of optics. And while computers are still involved with the initial designs of cinema lenses, many of them are assembled by the hands of experienced technicians. The human element ensures that quality is maintained down the assembly line. Some lens manufacturers even have one person assemble each lens from start to finish, rather than pass it down an assembly line. This extra step is not something seen on standard photography lenses. But what about the optics themselves? Do they perform differently? In short, yes—though a cinema lens costing 15 times more than your DSLR lens is not going to be 15 times sharper. That extra expense, in the case of the optics, is not just going toward sheer optical performance, but toward a higher level of consistency. Like their external structural build, cinema lenses feature optical designs that are far more consistent than their photography counterparts.
Starting with prime lenses, a quality set of cinema primes will match physically and optically. Lens coatings are similar across the set, so all the lenses will provide similar color rendition. Additionally, the most commonly used focal lengths will have the same aperture, measured in T-stops, as opposed to the f-stops on photography lenses. T-stops provide an absolute measure of the light passing through the lens, as opposed to an idealized mathematical ratio that measures f-stops. This consistency allows you to switch focal lengths during a shoot and not have to worry about imaging inconsistencies down the line, like in the coloring suite, where every minute counts. An additional measure of consistency is in the focus mechanism. Many photography lenses that employ “unit” focusing (where the entire optical assembly moves as a unit while focusing) display a phenomenon known as “breathing,” in which the frame will change slightly. In motion pictures and video, this can prove distracting while an otherwise seamless focus pull is taking place. Cinema lenses based on photography lenses will still exhibit the same breathing characteristics as their original design, and older cinema lenses (even ones without “unit” focusing) can also have a tendency to breathe.
Zoom lenses are even more advanced, both optically and mechanically. In addition to the provisions that prime lenses already make in the name of consistency, having to cover a variety of focal lengths and maintain optical consistency is even more difficult when you introduce the zooming capability. While focusing with cams is already a complex maneuver, zooming uses a similar cam-based process, but to move much larger element groups. While this alone would be enough to mechanically justify the expense, cinema zooms take it another step further. Cinema zoom lenses are true zoom lenses, as opposed to photography lenses, which are technically “varifocal.” What’s the difference? Zoom lenses maintain their focus position throughout the zoom range when properly collimated. Varifocal lenses do not, regardless of how well they are collimated. This concession is made in photography lenses because autofocus compensates for that aspect, and building varifocal lenses is significantly less expensive.
Photography Lenses for Cinema
Cinema lenses are special products that are priced to be bought only by those who need them. But, for the rest of us with DSLRs and mirrorless cameras that cost slight fractions of the price of a professional cinema camera, what do we do? Well, you go to the next best thing, cinemizing your current lenses. This topic itself is going to be covered more extensively in an upcoming article, though here are some quick tidbits. Some photography lenses can be modified to be more acclimated to the cinema world. Outfitting gears and de-clicking iris rings (when possible) might be enough to use these lenses on a video production. However, because of the tolerances harped on above, they will not be mechanically or optically as reliable or consistent enough for the most serious work. Breathing, color rendering, focus shift, and other issues will rear their heads more often because of this. However, if you develop a shooting style that can work around these factors, there is no reason to suspect unsatisfactory results. However, many filmmakers prefer older lenses, since they often have manual irises and mechanics superior to newer lenses with provisions for autofocus, though some newer lenses are beginning to adopt heavier all-mechanical designs as a throwback to older lenses, and those, I find, work very well for video. It may take some trial and error to find some good lenses that work nicely for your productions, but once you graduate to real cinema-grade lenses, it can be hard to go back.