When the Beattie
Intenscreen™ is used in 35mm SLR's, Medium Format, or
View Cameras, the user can expect an increase of viewing
brightness of 1½ to 4 f-stops depending on the camera
used. With the increased brightness it will become
easier to focus in low light or poor contrast
conditions, indoors or outdoors.
Beattie Intenscreen™ helps the user achieve fast and
accurate focusing while preserving detail and a brighter
image. Beattie Intenscreen™ bright focusing screens is a
combination of a specifically designed image surface and
a fresnel lens. This reduces the amount of light
required for image-forming and transmits the bulk of the
light to your eye. Not only does this improve your depth
of field, but it increases the sharpness of your own
vision. The Beattie Intenscreen™ is custom-tailored for
each type of camera to work best with it's features and
optics.
Standard Screen
Intenscreen
INSTALLATION IS SIMPLE
In camera models with interchangeable screens installation of
the Beattie Intenscreen™ is as simple as removing the present
viewing screen and replacing it with the Beattie Intenscreen™.
For some models of camera Beattie Intenscreen™ comes in
component form, in which case installation instructions are
included with the screen. The Pentax 6 x 7 and the Hasselblad
500C are the only cameras that require a technician to install.
Brightness Gains & In-Camera Light Metering
Depending on the camera, optics and accessories gains range from
1½ f-stops to 4 f-stops. Small format camera gain approximately
1½ f-stops; Medium format cameras 2 - 3 f-stops; and 6 x 7, 6 x
9 , 10cm x 12.5cm (4" x 5") and Panoramic Cameras 3 - 4 f-stops.
Metering systems that read off the screen (see your user's
manual) are affected by the Beattie Intenscreen™. The following
methods can be used to compensate:
Changing the ASA film speed - Using your existing screen, set
the camera lens at infinity and looking at an even light, such
as a grey card or blue sky, note the meter reading. Install the
Beattie Intenscreen™ and turn the ASA index dial until the meter
needle returns to the old screen reading. Record this offset and
tape to the back of your camera.
Changing the Exposure Value (EV) 1 EV = 1 f-stop - In modern
cameras there is a button that can manually change the amount of
exposure. Using your existing screen set the camera at infinity
and looking at an even light, such as a grey card or blue sky,
note the exposure reading. Install the Beattie Intenscreen™ and
push the exposure button until the exposure needle returns to
the old screen reading. Record this offset and tape to the back
of your camera. An essential part of the design of the Beattie
Intenscreen™ Plus bright focusing screen is that a very small
proportion of the light is used through scattering to form the
image and provide focus contrast. The remainder is transmitted
through the screen and collected in a narrow cone by the special
fresnel lenses used. The meter sensor cannot be in your line of
sight and so is slightly off axis. This means that it may be in
the "boundary layer" at the edge of the light cone and will
therefore not record a significant change even though your eye
may see major brightness changes.
Looking into the Future
Special screens have been made for medical, scientific and
industrial purposes ranging from 3mm to 52.5cm in diameter. A
few applications are, enlargers, custom printers, microscopes,
endoscopes, telescopes, back projections of all types. In these
cases Beattie Intenscreen™ will provide a better than twofold
gain in light transmission over conventional ground glass.
FOCUSING & CAMERA FOCUS
Critical lens focus on the film depends on installing the
correct components in the correct order. This should be
determined at the time of ordering. The installation should be
tested on a fine line target with high resolution film. If there
is any doubt of the very short depth of focus lenses are being
used, it would pay to have the camera checked on a collimator
(Camerascreens will not be responsible for any focus errors).
LIGHT METERING
External meter and the modern slide in meter sticks that meter
the image in front of the screen will not be altered. However,
the Beattie Intenscreen™ is BRIGHTER. If you use a meter with a
fibre optic probe (like Gossen) or an optical Type I spot meter
(like Litemate\Spotmate by Photo Research), then the absolute EV
readings will be different from any other screen, when you take
readings off the eye side of the cover plate. If you wish to
compare relative bright\dark areas, this works as before, but
for absolute exposure, the direct meter at the lens should be
used.
FRESNEL LENSES
The fresnel lenses on the back of the focusing screen are a 6"
effective focal length plano convex lens for 6 x 9 and 4 x 5
view cameras and a 10.45" effective focal length plano convex
lens for 5 x 7 and 8 x 10 view cameras, with convex portion
towards the eye. For optical calculations the fresnel side
conjugates are 6" and 10.45", both plano side conjugates are
infinity for the fresnel lens with 6" EFL and 10.45" EFL,
respectively. These choices suit most of the normal view camera
lenses.
Some points to consider: 1. If using a viewing attachment with a
mirror inverter, everything is OK. If there is a magnifier lens
included, it may cause vignetting and should be removed. 2. When
using short wide angle lenses (Super Angulon etc.) see use of
extra fresnel lens in the first part of this article. This is an
identical fresnel to the fresnel on the focusing screen except
it is installed with the plano convex side towards the other
fresnel. This makes a Ramsden pair, for least distortion, which
makes a combined focal length of about 3" which will cope with
lenses down to Super Angulon 47mm.
MISCELLANEOUS INFORMATION
The acrylic set back, glass cover plate, and extra fresnel lens
are all .060" thick. The focusing screen are 0.075" and 0.085"
thick respectively. A few cameras, especially older wooden
framed ones may require slightly longer screws. Do not over
tighten clip screws when installing, especially when using glass
cover plates. This also allows for expansion and contraction.
