Jim Frazier: Frazier Lens Swivil Tip and Image Rotator

From American Cinematographer, Seeing is Believing by Christopher Probst (February 1999)

Perhaps the most useful aspect of the Frazier lens is its dual swivel-tip design, which allows for unlimited 360-degree global orientation of the taking lenses. Simply put, the lens can be pointed in any direction, even back at the camera operator. The swivel tip incorporates heavy-duty bearings, which make the system extremely rugged and mechanically precise, and consists of two right-angle pivot points which can be turned independently and continuously in either direction. Internally, the image is relayed through the swivel via a mirror and an amici roof-edge prism.

"On any piece of optics with a roof-edge. The roof has to be made very accurately. Otherwise, you can end up with a double image on the film. The roof angle should be 90 degree plus or minus three seconds of arc, which is very small. Normally, these types of prisms are used in binoculars and other types of instruments that are used by eye. And the eye is actually quite forgiving. In the case of the Frazier lens, however, the amici's roof-edge images to film, so it has to be very accurate...

...There are obvious situations in tabletop work where it can be a difficult matter to even look through the viewfinder. But with the swivel tip, it's easy to leave the camera in a conventional setup and put the lens where you need it. Additionally, if you imagine the lens to be like your hand and arm, you can get the lens wherever you can put your hand. I've seen some extra-ordinary things done with the lens just for the comfort of the cameraman!

You also have added freedom in that the camera itself doesn't have to be level. For example, you can even get a level image if the camera is turned on its side under a car, simply by adjusting the image rotator. This system was designed to free up the difficult aspects of cinematography that are either too expensive or time-consuming. You don't want to have a jackhammer cutting holes in the floor to get a lens in a certain position. You can also save the costs of renting additional equipment like Panatates, dutch heads, low-angle prisms and hotheads. I have gotten reports back from other cinematographers that by using the Frazier lens, they've been able to literally chop days off their shooting schedules...

...Rotating an image with a prism is not a new thing. But by putting that function in this system with its large depth of field and a fully adjustable swivel tip, you create a new range of options. The image rotator is actually what is called a pechan prism. A pechan prism is common in other optical instruments, but in this case it had to be made to very tight tolerances. One reason for that, of course, is image quality, but another is that we have to keep the boresight constant. If you rotate the prism, you don't want the picture to spiral around too much...

...Every lens has to have some sort of filtering capability. However, if you put a filter in front of the Frazier's taking lens, you have to be careful about dust. I'm talking about things like tiny carpet filaments flying in the air that are attracted to the glass due to static charge. Therefore, with the Frazier lens, the best place to put a filter is inside the system, within the relay optics. The Frazier's filter slot is also a sealed unit — there are two glass windows inside to prevent dust from traveling up or down the tube — so you can have dust go into the filter compartment without producing spots on the film."

-Iain Neil (Then Panavision Executive VP of R&D/Optics)

Jim Frazier: Frazier Lens Advantages & Build

From American Cinematographer, Seeing is Believing by Christopher Probst (February 1999)

"This device does have a very large depth of field, but it is not infinite. The depth that is created does not break the laws of physics; it occurs because of the design of the optical relay system that is used. If you were to take a 10mm fixed-focal-length lens and put it on a camera, you'd get a certain field of view and depth of field at, say a T8 aperture. If you were to put the equivalent lens on the Frazier — which in this case would be the 14mm, which delivers about a 9.9mm field of view — you would actually have a similar depth of field. Now you may say, 'Wait a minute! If that's so, why do people talk so much about the depth of field with this lens? Why wouldn't they just rent a 10mm instead?' The reason is that with a 10mm lens, the diameter of the front element is about six inches. If you were to take a bumblebee and put it on that lens's front glass, it would only fill about five percent of your frame. Because of the Frazier system's optical configuration, when you put the bumblebee on the front of the 14mm taking lens — which is about an inch and a half in diameter — the bee will fill about half of your frame. Yes, you'd have a large depth of field, but more importantly, you're able to get objects really close to the front of the taking lens to get into macro magnifications. So in a practical sense, the Frazier system's depth of field is more available and useful.

Another problem with other lenses has to do with the entrance pupil of the lens. 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."

-Iain Neil (Then Panavision Executive VP of R&D/Optics)

"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."

- Jim Frazier, ACS

"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. 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 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."

-Iain Neil (Then Panavision Executive VP of R&D/Optics)