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.
The glass cover plate is scratch resistant and
anti-reflective coated on both sides. This gives maximum light transmission
and back light reflection suppression. This choice is ideal for studio and
location work, greatly reduces the eyestrain on complex set ups and long
working hours. The above description fits what we call Type 1 cameras, i.e
those cameras that originally had a ground glass screen only, or a ground
glass screen plus a separate fresnel between the glass and the eye.
The Type 2 cameras (for 10cm x 12.5cm cameras only) are those having a
fresnel lens between the taking lens and the ground glass originally. We
provide a part called Acrylic Set Back for these type cameras. This clear
acrylic part substitutes for the original fresnel and provides the necessary
mechanical thickness and optical set back to focus the image to correspond
with the film plane in the film holder. The focussing screen and cover plate
are then used as described (see copy of the "Installation Guide", which
describes this in more detail).
The Intenscreen can be ordered either plain (no markings), or with
grid lines (1cm grid with open centre) and crop markings (heavy lines, for
cropping, 6 x 7, 6 x 9, 6 x 12 format markings). The main grid lines are
.006" to 0.010" wide. Lines appear black when viewing.
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
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).
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.
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.
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.
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