Large Image Circle, Universal Usability: The Compact Prime CP.3 and Cinema Zoom CZ.2 Lens Families
With the emergence and proliferation of digital cinema cameras with large sensors, the demand for corresponding interchangeable lenses has also seen a sharp increase. Yet not all of them fit and satisfy the requirements of the large sensors that require lenses with the ability to project a larger field of view. With its CP.3 and CZ.2 families of lenses, ZEISS offers a universal solution in this regard.
Building on the success of the CP.2 lenses, the new CP.3 version will soon be part of the standard assortment of lenses offered by equipment rental companies across the globe – There are a total of ten CP.3 Compact Prime lenses available with fixed focal ranges from 15mm to 135mm, as well as three Cinema Zoom CZ.2 zoom lenses with zoom ranges of 15-30mm, 28-80mm, and 70-200mm. All of the lenses are available with the five most common mounts for motion picture cameras (PL, EF, E, F & MFT) and offer full-frame (36 x 24 mm) coverage of the image circle.
Up into the early 1980s, there were two main formats available for professional film work outside of the television studios – 16 mm and 35 mm film, with 16 mm having a smaller field of view and 35 mm offering a field of view about four times as large.
The development of video technology then brought along cameras – aside from smaller formats and those used by studios – with a usable sensor size about equal to that of a 16 mm frame. In the beginning, television tubes converted the optical information into video signals, later CCD sensors were used as the image information could be processed digitally. Soon, CCD technology was used not only for standard definition, but HD as well (with 1280 or 1920 horizontal pixels). But the beam-splitting prism that was required as a result of the three-chip technology, and the associated large flange focal distance largely prevented the use of interchangeable lens or even just switching between 16 mm and 35 mm film lenses.
Two technological developments changed the landscape decisively beginning in the mid-2000s, however – electronic single-chip cameras with a sensor about the size of 35mm film (CMOS technology), and about five years later, the discovery that you could shoot video with digital single-lens reflex still photography cameras.
A Larger Sensor – Why?
It was a desire for a higher resolution on the carrier medium that drove development toward a large sensor. The amateur and the first standard video formats the television and film industry used beginning in the 1980s for lower-quality productions, were too far off from the fine resolving power and dynamic range of chemical film. These formats did not come anywhere close to 16 mm film. But little by little, the industry succeeded in manufacturing light-sensitive chips with reliable quality at acceptable prices that were larger than the previous 2/3″, 1/2″, and 1/3″ sensors. In principle, this made the long-held desire to have a 35mm frame size digital movie camera with an electronic storage device instead of a reel of film, a reality. Sony came up with the F-35, and a small Californian company RED Digital Cinema pressed ahead with its RED One, while other camera manufacturers like ARRI went down similar paths.
In addition to a higher resolution thanks to increased space for light-sensitive pixels (photosites) and increased space for more pixels, the large frame (which a light-sensitive chip can now also have) offers the following two further benefits: Depth-of-field characteristics and blur reproduction.
A well-known law of optics states that a lens’ focal length and angle of view are directly proportional to the frame they are reproducing. This means that a larger frame with the same angle of view requires a longer focal length. While the 35mm is considered a kind of normal lens for 35 mm film (in Super 35), for example, for the same angle of 39° that is popular in medium-shot scenes in Super 16, you need a focal length of 18mm, and in 2/3″ about 15mm.
If you want to achieve this angle of view with a full-frame camera like a Sony A7S or RED Weapon 8K VV, whose sensor is a little bit wider than full-frame, you need a lens with an even longer focal length like a 50mm. A side effect of longer focal lengths invokes another law of optics: the longer the focal length at the same aperture, the more shallow the depth of field. Image planes can be better separated, details in one plane emphasized, image elements in the background and foreground appear more blurred and distract the viewer less.
Reflexes, objects, and shapes in out-of-focus areas grow larger and more blurry the larger the field of view and the longer the focal length. In addition, the distortion is dependent on the design of the iris diaphragm. The more individual aperture blades in the iris and the more the rounder the edges, the rounder and softer this blurring is, the more pronounced a lens’ bokeh. ‘Bokeh’ comes from the Japanese word boke, which means ‘blur’ or ‘haze’ considered aesthetically pleasing and harmonious. Lenses with larger diameters and larger fields of view enhance the bokeh, similar to larger apertures. In addition, bokeh is usually considered more aesthetically pleasing when the blurring artifacts appear uniformly in different areas of the image. A lens’ bokeh is an important artistic design element.
Large Fields of View, Large Image Circles
Cameras with large sensors require lenses that can completely fill that larger field of view. The explosion of digital cameras with large chips resulted in a spike in demand for the lenses made for 35mm film available on the market, such as those that can fully fill large sensors or at least sensors as wide as Normal 35 (22mm x 16mm) and Super 35 (24.9mm x 18.7mm).
And in this case as well, a simple law of optics applies: to fully display an image, a lens’ image circle must have a diameter at least as large as the field of view’s diagonal. Otherwise, the corners of the image will become dark or, cut off entirely. Lenses designed for the 16mm format cannot be used with large-sensor cameras. Older 35mm film lenses, with an image circle of up to 30mm, usually only cover 22mm x 16mm.
The digital cameras that were suddenly used for filming (for example the Canon 5D III, Nikon D810, Sony α7S, etc.), with their chips the size of a 35mm still camera’s field of view (36mm x 24mm), could initially only be used with the lenses designed specifically for them. The drawback, however, is that still lenses have short focusing paths, no suitable sprockets for external follow focus systems or motorized focus and aperture controls, and sometimes lack mechanical aperture controls, which makes them difficult to use in a professional film setting.
ZEISS Compact Prime CP.3 and Cinema Zoom CZ.2
In light of this new demand, The CP.2 prime lenses released in 2010 offered full format coverage (36mm x 24mm) with a new cinema housing featuring standardized dimensions. ZEISS equipped them with an iris diaphragm of 14 aperture blades, optimized the order of the lenses, improved the coating, built in light traps, and added special finishes to the lens edges to reduce stray light and uncontrolled flares. In doing so ZEISS guarantees constant image quality across the entire aperture speed range. Calibrated scales, 300° of focus rotation, standardized module 0.8 sprockets, a standardized front diameter (114mm to 100mm), a standardized housing length (80mm to 85mm), and a standardized weight are all beneficial for day-to-day film production operations.
Now the CP.2 lenses have again been updated with the new CP.3 version. Compared to the CP.2 lenses the new CP.3 lenses have a front diameter of 95mm. In addition, the CP.3 have an extraordinarily smooth focus rotation even in extreme temperature conditions. Also, lens coatings have been improved to offer a higher contrast with reduced reflexes.
The three Cinema Zoom CZ.2 lenses are newly developed and feature a modern lens design. Out of all the compact zoom lenses on the market, the three CZ.2 lens models with focal lengths from 15mm to 200mm cover one of the most extensive focal length ranges. Thanks to separate components for zoom and focus, ZEISS eliminated bouncing and focus changes while zooming. With each model weighing about 2.6 kg (5 to 6lbs) and having a front diameter of 95mm (CZ.2 28–80 and 70–200) and 114mm (CZ.2 15–30), they are relatively easy-to-handle, have standardized gear and scales, and are equally well-suited for more demanding production jobs as the CP.3 prime lenses. ZEISS also guarantees that colors match with its Compact Prime lenses. Also, at this point in time, the ZEISS Cinema Zooms are the fastest zoom lenses available for full frame sensor coverage, with a wide-open T-stop of T2.9.
All of the mentioned Cinema Primes and the Zooms have two key features in common: They are available with the five choices of lens mounts – PL, Canon-EF, Nikon-F, Micro Four Thirds, and Sony-E -, and they completely cover the full-frame format of 36mm x 24mm. This means they can be used with almost every digital camera with a large chip as well as a number of traditional movie cameras.
If using the lens with a RED Weapon 8K VV camera, there is a small limitation when filming in 8K full frame mode. At extremely short focal lengths, a slight vignetting effect may occur, particular at maximum open aperture with the CZ.2 15–30/T2.9 at the shortest focal length and the CP.3 15/T2.9. With the CP.3 15/T2.9, it helps to stop down slightly to reduce the vignetting effect to an acceptable level. With the CZ.2 15–30/T2.9 zoom lens, using the widest focal length results in slight vignetting, while from a focal length of 16 mm onwards, the dark corners disappear and vignetting is barely visible at even longer focal lengths. With the ZEISS CP.3 XD version (eXtended Data) correcting this will not be a challenge. Using the eXtended Data technology implemented on CP.3, it is extremely easy to eliminate the shading in post-production thanks to the lens profiles provided. If you want to learn more about ZEISS XD please continue reading here.
When operating the RED Weapon VV in 8K WS, 8KHD, or 6K FF mode (with sensor size cropped to 30.7mm x 15.8mm), vignetting does not occur, since the image lies far within the full-frame format. In addition, the 8K Weapon VV is often used with the goal of capturing a larger field of view than required for final output.
When using the CP.3 or CZ.2 lenses in the Weapon’s 8K mode, there’s a tolerance zone in the image circle, however. Achieving sufficient imaging performance at the edges is still possible in many cases, even if the larger image circle no longer lies within the specification of ZEISS lenses.
As a result, overall the CP.3 and CZ.2 lens families from ZEISS, with complete coverage of the full-frame image circle and interchangeable mounts, are an extremely comprehensive range of lenses for almost every motion picture camera available on the market today. This all-round usability means that the lenses are a safe, future-proof investment in case you should want to upgrade later to a new generation of camera sensors.