ARRI Ultra Prime T2.8/8R - Manual (Page 2)

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• has the focus and iris rings in the same position as the other Ultra Primes for fast and easy lens changes and
• shares the same robust and reliable construction that is appreciated by rental houses since it minimizes downtime.
Because the Ultra Prime 8R has an extremely wide angle of view, it does not work with most regular matte boxes, necessitating a
new front shade for the ARRI Lightweight Matte Box LMB-4. With this new shade, the LMB-4 becomes the LMB-4A.
When mounted on the Ultra Prime 8R, the LMB-4A can accept two 6.6 x 6.6 filters. A new set of masks allows the LMB-4A to
still provide ample flare protection for the longer Ultra Primes.
The Ultra Prime T2.8/8R extends the range of Ultra Prime lenses at the extreme wide end. Together with the 10, 12,14 and
16 mm Ultra Primes, these lenses provide the most complete wide-angle selection in any modern prime lens set. Thus the
Ultra Primes now offer 16 different focal lengths for every cinematic need, from the only telephoto lens designed specifically for
motion pictures, the Ultra Prime 180 mm, to the new Ultra Prime 8R, giving you the flexibility to get the coverage you
want.
What is 'Rectilinear'? What is a 'Fisheye'7
When a lens projects a three dimensional scene onto a two dimensional piece of film, not all geometric properties of the
original scene can be maintained. This is essentially the same problem as mapping the shape of the continents of our three
dimensional globe onto a two dimensional map. The choices of lens design, focal length and distance to the subject determine the
character of this mapping, which is commonly referred to as perspective, one of the cinematographer's most important
tools. For wide angle lenses, the lens designer must make a choice between a rectilinear or a flsheye lens design, with
different consequences for perspective. The most obvious differences can be seen by how straight lines and objects at the
edge of the frame will appear.
Since the human eye judges distance by the way elements within a scene diminish in size and the angle at which lines
converge, most lenses are designed to duplicate those „natural“ geometric relationships on film. This is called a rectilinear
perspective, and to achieve it the lens will stretch the image so that vertical, horizontal and diagonal lines that we perceive
as being straight are reproduced as straight lines on film.
There is, however, a limit as to how wide a lens with a rectilinear perspective can be, based on the limited amount of space
available in front of the camera, and on various optical problems that get increasingly unwieldy as the angle of view
increases. The 122° diagonal angle of view of the Ultra Prime 8R is already at the limit, making it a unique and unusual lens
for the cine as well as the still photography field.
For this reason many extreme wide angle lenses are designed as fisheye lenses. A fisheye lens can have a wider angle of
view than a rectilinear lens. But it maps the scene to film differently than we perceive the world around us, because the
focal length is actually changing within the image. The farther a straight line is from the center of the frame, the more it
will be rendered as curved, and objects at the edges of the frame will be heavily distorted with the typical fisheye look.
A rectilinear wide angle lens on the other hand renders all straight lines in the subject as straight lines in the image, though
there is linear stretching applied to the image that Increases as an object gets closer to the frame edge. This effect tends to
exaggerate perspective, i.e. it will make rooms appear larger than they are, enhancing the illusion of depth. However, a
circular object, like a ball or a person's head, located near the edge of the frame will appear to be somewhat enlarged and
will have an oval shape.
Neither fisheye nor rectilinear extreme wide angle lenses represent reality in quite the same way as we see it, but they
provide two different ways to manipulate perspective, to change the illusion of space and distance.
To the right arc some sample images taken with a rectilinear and a fisheye still photography lens to illustrate the two
different looks.