NAB 2009 - New PL Mount Lenses
It's all RED's fault: an explosion of PL mount lenses. Here's what I found at NAB.
By Adam Wilt | April 27, 2009
As soon as the RED ONE was announced, the market for PL mount lenses capable of covering a Super35mm-sized image started heating up. Aspiring R1 owner/operators hunted down almost every decent used lens available, and caused the lead times on new PL mount glass to skyrocket. At NAB '09 several vendors stepped forward to fill the demand, mostly at bargain prices (at least by traditional cine lens standards).
This new generation of lenses reflects several trends:
- New designs following the form and function of traditional cine lenses, but with lowered costs.
- Reworking or "rebarreling" of still-camera lenses to meet the needs of cinematography.
- Designs that optimize price/performance ratios at the expense of traditional cine lens virtues.
- Digital-specific lenses that extend rearward into the space normally occupied by optical viewfinder hardware like mirror shutters or beamsplitters.
"Traditional" cine primes and zooms aim for certain specific physical characteristics that set them apart from their still-camera and video counterparts.
Both primes and zooms aim for low gearing / long throws (amount of travel) on all their controls; they typically require as much as 270 degrees of rotation or more to traverse the focus scale, and their iris and zoom controls similarly require more turning to go from end to end than on still or video lenses. Long throws allow for smoother and more precise operation, very important when every hiccup is magnified on a big screen. Still and video lenses, by contrast, optimize speed of operation with short throws / high gearing.
Cine lenses require consistent feels and forces throughout their operating ranges, again to optimize the smoothness and consistency of manual zooms, focus pulls, and iris changes. Still and video lenses benefit from this sort of smoothness, too, but it's not as critical, especially on still zooms: if the last 20% of a zoom range is a bit stiffer and geared a bit differently than the first 80%, it's not that big a deal, because the still shooter isn't trying to run consistently through the zoom range while shooting.
Sets of cine primes are often matched in maximum T-stop, length, front diameter, weight, center of gravity, and placements of controls, and they often use internal focus designs. All of these factors allow lenses to be interchanged without affecting balance (important whether handheld, tripod-mounted, or on Steadicam), lighting (consistent T-stops), or the adjustment of lens accessories like matte boxes or follow-focus controls. Internal focus designs allow running through the focal range without varying the lens barrel's position, so that the front of the lens stays neatly ensconced in the matte box's "doughnut", keeping stray light out and maintaining a fixed spacing between the front of the lens and any filters.
f-stops are calculated aperture openings; the "f" refers to a fraction of the focal length: f/2 means the aperture diameter is 1/2 the focal length. F-stops are used on still and video lenses, and are the basis for depth-of-field calculations.
T-stops are f-stops adjusted for lens losses; they are measured settings giving the same exposure as a "perfect" lens would at the calculated f-stop. Prime lenses normally have f-stops and T-stops that are nearly identical, but complex, long zooms may have T-stops that are as much as a full stop slower than their f-stops, due to internal reflections and absorptions.
T-stops are normally used by cinematographers, who have traditionally not had through-the-lens metering to compensate for any lens-induced light losses. T-stops allow swapping between widely differing lenses while keeping the exposure constant, without having to calibrate one's light meter for each and every lens separately.
Cine zooms also need to hold their maximum aperture throughout the zoom range, without "ramping". Many popular still zooms ramp from f3.5 to f5.6 as they zoom; it's no big deal for the camera to vary shutter speed or gain as needed. Many video zooms hold a consistent aperture for much of their range but will lose half a stop to a full stop at full telephoto. Again, in typical ENG work, the camera compensates with a shutter or gain change, or the image just goes a bit darker at full tele and no one worries too much about it. In film-style work, consistency is key—but having a long zoom with a wide maximum aperture results in large front diameters, complex designs to cope with aberrations, and size and weight gains to match.
Lenses designed for film cameras also need to ensure sufficient space between their rearmost elements and the film plane to make room for an optical viewfinder's intrusion into the light path, whether a mirrored shutter or a beamsplitter mirror or prism. Keeping that space clear, especially on wider primes and zooms, complicates the design considerably.
All of these desirable characteristics add expense, of course, which is why a typical T2 prime lens costs about US$12,000-$20,000, and a T2 3x zoom often runs around $50,000.
New lenses at NAB 2009
To make cine lenses more affordable requires making compromises of one sort or another, and different vendors have taken different approaches. Note that I'm not going to say anything definitive about optical quality in what follows (other than what I find in Zeiss literature, comparing different Zeiss lenses with each other); NAB isn't the place to evaluate and compare lens performance. I'm simply going to look at mechanical properties of the lenses, and leave optical evaluations for future tests under controlled conditions.
Zeiss Compact Primes at BandPro's booth, one mounted on a Red One.
I've already mentioned the Zeiss Compact Primes. Again, it's a seven-lens set for around US$40,000:
- T3.6 18mm Distagon T*
- T2.9 21mm Distagon T*
- T2.9 25mm Distagon T*
- T2.1 28mm Distagon T*
- T2.1 35mm Distagon T*
- T1.5 50mm Planar T*
- T1.5 85mm Planar T*
These lenses are based on the Zeiss ZF line of still camera lenses, but these haven't simply been rebarreled with PL mounts; the mechanics are very much cine lens housing with the same long throws and silky-smooth, consistent mechanisms as Zeiss Ultra Primes and Master Primes.
Compared to the T1.9 series of Ultra Primes, Compact Primes are much the same size, weight, and "feel": they're very slightly lighter, a bit more tapered towards the rear, and somewhat shorter and fatter. Ultra Primes run around $13,000 each; these are less than half the price. How?
The most obvious difference is the variance of the maximum aperture. While T1.5 on the tele end is rather nice, T3.6 on the wide end can be a bit of a limitation. If you look at the FAQ on the Zeiss page, you'll see that the Compact Primes aren't as highly rated as Ultra Primes (or the even more expensive Master Primes) in terms of performance across the f-stop range and at close focus distances; evenness of illumination (vignetting); and precise color matching. Additionally, the iris scale is not linear; as the lens stops down, the stops get closer together on the iris ring.
For less than half the cost of an Ultra Prime, I could probably suffer through these limitations, grin. And if I were throwing a RED on my shoulder or on a Steadicam, the Compact Primes might be my first choice just based on weight alone: they run 0.9-1.0 kg, or about 2.2 pounds.
BandPro carries 'em in the USA.
RED Pro Primes.
The RED Pro Prime Set consists of five lenses for US$19,000:
- T1.8 25mm
- T1.8 35mm
- T1.8 50mm
- T1.8 85mm
- T1.8 100mm
(One can add the T2.9 300mm for $4000 if bought at the same time!)
These are big, solid cine lenses, with smooth zoom and iris rings (if the prototypes RED displayed are any indication). But you'll observe that the 25mm and 35mm are longer than the others; you'll have to move your matte box when you change between the normals and the teles, even though the focus and iris rings are consistently located so your focus and iris controls can stay put, and all the fronts are 110mm across.
The lenses are heavy, too; the short guys are about twice the weight of Compact Primes or Ultra Primes at around 4 pounds, while the long ones are three times the weight: 6 pounds. This doesn't matter much on a tripod (though the step change between the 35mm and the 50mm will require rebalancing) but for handheld and Steadicam every extra ounce is begrudged.
These lenses also depart from current practice in having designs favoring aggro sleekness over readability: iris and focus scales are only visible through cutouts in the barrels, and the focal length marking is embossed in the housing but not filled with a contrasting color. While these are minor quibbles, they make it a bit harder to see what lens you've got and how it's set, especially in low light. When you look at a Master Prime or RED's own 18-50mm or 50-150mm zooms, with their fluorescent scales and labeling, RED's choices are puzzling.
uniQoptics "Signature Series" PL mount lens set.
uniQoptics announced the "Signature Series" primes at NAB; a set of five will set you back US$24,000:
- T1.9 25mm
- T1.9 35mm
- T1.9 50mm
- T1.9 85mm
- T1.9 100mm
It's similar to the RED Prime Set in many ways: same focal lengths and nearly the same maximum aperture. Like the REDs, the 25mm and 35mm are longer and heavier than the others; they're 5.75 pounds while the shorter 50, 85, and 100mm lenses are 4 pounds. And they're big, too.
Once school of thought I heard bandied about at the show was that the lower-cost lenses from RED and uniQoptics eschewed costly low dispersion glass for thicker but cheaper elements, thus gaining weight and bulk as the tradeoff for lower price. uniQoptics says specifically they use extra-low and super-low dispersion glass, so I'd have to say that there must be something else at work.
Like the REDs, these lenses use recessed focus and iris scales, though the markings are perhaps a bit more visible. At least the focal lengths are visibly marked on the side of the lenses.
UniqOptics 85mm T1.9 PL mount prime. Note hand-marked prototype to the right.
These lenses are made in the USA (I didn't even know that was even allowed any more!) by a company that specializes in customized and high-G lenses for commercial and military clients.
The design is claimed to be optimized for digital sensors. It's unclear if either these or the RED lenses can be used on a camera with an optical finder, or if the rear elements would protrude into the space occupied by a mirror or beamsplitter.
Next: Rebel, IB/E, ISCO, Century, Focus Optics, Angenieux, and Fujinon...
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