"Another problem with other lenses has to do with the entrance pupil of the lens," Neil expands. "With a lens that has a six-inch diameter, the entrance pupil is actually some distance inside the lens. So as you bring your face in close to the lens, your nose will start to bulge and your ears do something weird with perspective distortion. With a smaller-diameter lens, the entrance pupil is still inside the lens, but at a much smaller distance [from the front]. If you look at the mathematics, it turns out that you could then bring someone's face all the way up to the lens and not see any perspective distortion. This relationship has a lot to do with how the taking lenses, the field lenses and the system have been optimized, which in this case is in the area between six inches and three feet. When you can't see the perspective, you can't tell the size of an object or the distance it's at, so a sort of optical illusion is created."
Adds Frazier, "With the Frazier lens, macro work has never been easier. A cinematographer now has an unparalleled freedom of movement in the macro range. In fact, unlike conventional macro lenses, there is no pull-focus necessary. The camera can simply float in and out on the subjects without any loss of focus and without any distortion or curvature of field — even when the subject is almost touching the lens. This is particularly invaluable for scale model and tabletop work, where both depth and distortion are major issues. I knew from my commercial work that when you put a product close to the lens, you don't want to see this great curved field. I love playing with perspectives [and the perception of perspectives,] so I concentrated on building these units without any distortion. In my earlier prototype units, the illusion — which I knew was there — was ruined because of distortion. In commercials, clients usually don't like to see their products distorted. If the product has straight lines in it, they want to see it [photographed] with straight lines."
The Frazier Lens
After several years of design efforts and optical fine-tuning, the Frazier lens was made available to the cinematographic community. The system, based on Frazier's optical design, utilizes further optical refinements by Neil — who worked in conjunction with Frazier — and mechanics crafted by Rick Gelbard. It was designed to be extremely versatile and rugged, provide extreme levels of depth of field, and to mount on the front of a camera like any other lens.
In its finished form, the Frazier lens system features a dual swivel tip, an internal image rotator/de-rotator, and an in-line, drop-in, multiple-filter slot with an external thumb wheel for polarizer filters. Imaging is provided by a set of optimally-chosen, modified still photography lenses which attach to the front of the Frazier's main tube. While there were initially seven taking lenses included with the system, Panavision has added four new focal lengths to this array (see table p. 90). All of the lenses are calibrated to deliver the system's currently widest T7 aperture.
Frazier, Neil and Gelbard were recognized for their efforts in 1998 by the Academy of Motion Picture Arts and Sciences with a Technical Achievement Award.
Taking Lenses
"One significant aspect of the Frazier lens which may not be obvious is that the taking lenses — which also house some field lenses — are designed as sealed units," Neil submits. "With the Frazier taking lenses, you're actually getting a taking lens plus part of what really goes in the tube of the main system. In other systems, if you stop down to a T8 or T11, or all the way down to T32, you can have a major problem with dust. If there's one little particle near an intermediate image, you could end up seeing that speck on the film. But with a sealed taking unit, you can pretty much avoid dust. Of course, you still have to keep the optical instrument clean, but at least we have avoided the most likely cause of dust showing up on the final image."
The 11 taking lenses now offered with the Frazier system were selected for their excellent image quality and consistency following a survey of all available optics. It should be noted that the Frazier's internal relay optics reduce the focal length of the taking lenses, so the overall system delivers a wider field of view than marked by the respective lenses' manufacturers. Additionally, no focus or aperture adjustments are made on the taking lens itself; those functions are locked off. These adjustments are instead made at the rear of the main unit via controls located just behind the image rotator, and are standardized to accept all Panavision accessories.
Of the four new focal lengths recently added to the selection, one (a 14mm) is a shorter than the original set — delivering an even greater depth of field — while three others are longer (85mm, 105mm and 135mm). Notes Neil, "The longer focal lengths illustrate why increased depth of field, in itself, is not the only selling point of the Frazier lens system — it's a combination of features. For situations where you may not want the object right up to the lens, but you still want the flexibility of the swivel tip, the image rotator and the larger depth of field, we've added the 85mm, a 105mm and a 135mm, which respectively deliver 60mm, 75mm and 95mm cine fields of view. These longer lenses still offer a large depth of field, but it will start at perhaps 2 to 4 feet and then go to infinity."
[ continued on page 4 ]
© 1999 ASC