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MillimeterLenses for the Digital Era
Jul 1, 2003 12:00 PM, By D. W. Leitner
Classic Zeiss Superspeeds beget latest DigiPrimes.
If Zeiss' new DigiPrimes seem to be in a class by themselves, there's a history. That history goes back to the early days of lenses for film cameras and now shapes the primes that Zeiss builds for digital cameras.
Outside of Panavision, which designs lenses solely for its own cameras, only three major names in motion picture lenses survive into the digital era: Cooke, Angenieux, and Zeiss.
The British firm Cooke, on its own again after decades of management by the Rank Organization, was known in the late 19th century for its breakthrough triplet designs.
 Zeiss DigiPrime digital lenses—modern descendents of the Superspeed lenses—provide detail and clarity to images destined for the largest screens. |
But the oldest roots belong to the German firm Zeiss, whose founder Carl Zeiss set up shop in Jena in 1846 to make microscopes and other optical instruments. By the time motion pictures arrived in the late 19th century, the Zeiss firm had already invented the first distortion-free lenses. By 1936 it had patented the technique for anti-reflection coating — to this day marked T* on Zeiss lenses — that defines the superior contrast reproduction of modern lenses.
The hugely successful Zeiss enterprise remains at the forefront of the world's breakthroughs in telescopy, microscopy, ophthalmoscopy, and medical imaging in general, as well as photography.
Although motion picture imaging has never occupied more than a small corner of Zeiss' overall activities, Zeiss nevertheless enjoys a history of elevating performance parameters of primes in particular.
In the late 1970s and early 1980s, the introduction of the Zeiss Superspeed primes for 35mm and 16mm demonstrated that high speed and high performance were not mutually exclusive. There was simply nothing else like them at the time, especially in 16mm: perfect color and contrast matching, total freedom from aberrations, and corner resolution the equal of center resolution at all apertures.
They were called Superspeeds because they were designed to be used at their maximum aperture of T 1.3 or 1.4. This was a striking departure from prior lens designs, which required a stop down to T 4 or 5.6 for best results.
 Zeiss' Sharp Max uses the collimated image of an illuminated Siemens Star to indicate when backfocus is optimally adjusted. The tube-like device fits over the front of the lens. |
Film speeds at the time were climbing upward from 100 E.I. (exposure index, akin to ASA) to 250 and 320 E.I. The combination of Zeiss' Superspeeds and these faster films encouraged new styles of low-light cinematography to emerge, particularly in 16mm. The fact that 16mm Superspeeds by design also covered Super 16mm laid the groundwork for superior 35mm blowups, which in turn stimulated the American independent feature film movement in the early 1980s.
Many don't realize that the market for moving picture lenses is tiny compared to consumer and professional still photography — think of all those Hasselblads, Contaxes, and Rolleiflexes sold over the years — or that the design challenges are significantly greater. While the dimensions of 35mm and 16mm film are miniature compared to those of still photography, their images are magnified onto large screens to a scale far beyond anything typical of still photography. Lenses designed for cinema cameras must therefore deliver extraordinary detail and clarity.
Challenges to lens design are even more formidable in the digital era as we come to expect digital moving images that rival those of motion picture film. The output of HD cameras like Sony's F900 is increasingly compared (fairly or not) to 35mm, yet the active area of a 16:9 2/3in. CCD, for which the DigiPrimes are designed is smaller than a 16mm frame. Considering that HD cameras, like all 2/3in. CCD video cameras, interpose a thick, convoluted prism system between the lens and CCDs, the accomplishment of Zeiss in creating what are simply the best B4 mount primes in digital video — optimized, like classic Superspeeds, for use at their largest aperture — grows clear.
The current series of DigiPrime Distagons (a designation for the Zeiss wide-angle retrofocus design shared also by Superspeeds and still lenses) includes 5mm, 7mm, 10mm, 14mm, 20mm, the new 28mm (introduced at NAB in April), 40mm, and the new 70mm, which brings a macro-like capability of focusing inches from its front element (available by year's end).
All are T 1.6 (except the 5mm, which is T 1.9) and feature a uniform barrel diameter with identical focus and iris gear positions — important for rapidly swapping lenses in and out of follow-focus devices. The lenses also feature a common 95mm front diameter and 164mm length (the 70mm will be 194mm), enabling use of the same matte box position and donuts.
The DigiPrime's sealed internal focus design, which first appeared in cine zooms in the 1980s and which Zeiss, in close collaboration with Arri, adapted to its state-of-the-art UltraPrimes for Super 35mm in the late 1990s, results in a front barrel that neither rotates or expands. This simplifies the use of DigiPrimes with rod-mounted matte boxes and permits alternate use of lightweight clip-on matte boxes. Zeiss' internal focus/floating element design also eliminates image breathing during focusing.
Other welcome features include the large, phosphorescent green focusing and iris scales thoughtfully engraved on both sides of the lenses. The fat barrel and 300-degree focus ring rotation result in wide, evenly spaced focus marks appreciated by any camera assistant who marks and pulls focus on a DigiPrime. The use of a windowed focus scale like the best 35mm Zeiss and Cooke primes is a nice touch too.
Excellence, however, comes at a price. The small market for top shelf digital lenses — and primes in particular — and the exacting challenges of superior small-format optical design only exacerbate the problem of high cost for lenses such as these.
So it took guts and commitment for Band Pro Digital, a prominent Los Angeles rental house, to step forward and advocate the viability of these lenses in the face of present marketplace conditions. Band Pro convinced Zeiss that these matchless lenses could succeed despite all uncertainties and play an important acquisition role in high-quality digital cinema and television.
OK, so you accept the fact that DigiPrimes upgrade the look of any B4 mount camera, from an interlaced standard-definition Sony DSR-500 to a progressive-scan, high-definition Sony HDW-F900. And that corner-to-corner sharpness, shadow detail, and color saturation visibly improve as a result. Maybe you agree that shooting wide-open at T 1.6 not only produces great-looking images with 35mm-like shallow depth-of-field (T 1.6 in 2/3in. HD approximates T 2.8 in 35mm), but also lowers the lighting bill. How do you afford to get your hands on them?
Rental is the answer for most, and DigiPrime sets are beginning to show up in rental houses. They're in demand, however, and won't come cheaply at first, but it may be worth asking if the project is right.
One more thing about DigiPrimes. Because Zeiss makes them, and because Zeiss also designs and markets a wide range of optical test equipment (including laboratory and bench units for testing Modulation Transfer Function and a unique T-Stop Tester), Zeiss decided to introduce alongside the DigiPrimes a new type of backfocus tool. This tool uses the simple collimated image of an illuminated Siemens Star to indicate when backfocus is optimally adjusted, a significant source of worry for many HD camera operators. The tube-like device, called Sharp Max, fits over the front of the lens on the camera. By means of the DigiPrime backfocus adjustment, the Siemens Star pattern is adjusted to maximum sharpness on the HD monitor. It's that simple.
Not only are Zeiss DigiPrimes in a class by themselves, but so is Zeiss. For more information on the history of Zeiss and DigiPrime and Superspeed lenses, visit www.zeiss.com.
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