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)

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