CONTROLLING SCREEN AND SHUTTER
by J.C.M. van den Berg
This concerns the against-the-light camera, which can cope
with information of high contrast.
The reason for developing it was the until recently existing
limitation, that one could not take photographs into or against
full sunlight - thus with the full sun in the picture, - because
this led to practically complete overexposure of the intended
This was the challenge: to go against this well known
conception, in spite of all that, and to find a method which
would allow photographing against full sun light or against
other light sources or to fiercely lighter areas, so that
afterwards - depending on the findings - other properties and
other applications possibly could be discerned.
When you first look at other well-known practical applications
of camera systems, it appears that - with the most current
systems - projection of the picture on sensitive material is
done via two sorts of shutter systems, namely:
Firstly the in-between-the lenses-shutter.
Secondly the focal-plane-shutter.
Here is a short summary of the differences between the two
in-between-the lenses-shutter is found in the object-lens or
beneath in the near vicinity of it.
focal-plane-shutter is located just in front of the
photosensitive recording material.
Regarding the function:
in-between-the-lenses-shutter allows, for a split second, the
whole image projection to fall on the photosensitive material.
focal-plane-shutter in the same way lets a longer existing image
projection fall successively strip-wise on the photosensitive
Both systems have their advantages and disadvantages, in an
optical sense as well as from a technical construction point of
What is striking here, is the fact that objectives
"with an open eye" - as it were - "look at"
the space around the object.
When the sunlight falls in a slanting direction a sun-hood is
then quickly put to use.
It is therefore clear that the sun as a light source in the
object space, which is the space out of which the information
must be obtained - can have prolonged access to the
object-lenses. This makes coping with the information as a
result of overexposure and/or internal reflections in the
optical system rather problematic.
What then is the principle of the against-the-sun-camera?
Well, in this camera a new type of shutter system is applied,
with which the object- or image space is scanned. Thus, by this
means, the object space is successively, hence in portions,
allowed to reach the lens or lenses of the camera. Furthermore,
during this scanning the photosensitive material is protected as
far as possible against information disturbances by means of a
screen - situated just in front of the photosensitive recording
material - in which a slit-shaped opening is found.
The shutter system - so called integrated shutter - consists
therefore of two parts working together.
One part - the slitter screen system of a particular
construction - is placed in front of the object-glass, and
carries out the actual scanning of the object space, and the
second part is placed behind the object-glass, namely just in
front of the photosensitive material, and screens the recorded
information and the information yet to be recorded from
interference, which results from reflections in the whole
This letter part, although the second part as an element in the
constructions is more or less similar to the known
focal-plane-shutter, is in its function however, completely
The system in front of the lens(es) consists of a number of slit
lathes which are set up such, that 'parallel' beams
of light are formed, which are afterwards built up into a strip
image by the lens system. These slit lathes were chosen instead
of parallel partitions - so named high blinds - and this was
caused simply by the unacceptably large number of reflections
which would occur with the use of partitions, no matter how well
they were also fitted with low reflection or light absorbent
material. Because of the choosing of lathes, which then have to
be as thin as possible against the edges of the slit, these
reflecting surfaces were avoided. However, this is at the cost
of somewhat more than half of the effective lens surface area,
which is comparable to well over a diaphragm stop. This is not
such an objection with today's optical technique, as rather high
light intensity objectives are in vogue.
The scanning takes place by moving the lathes relatively to each
other or by moving the whole lathe system as one fixed whole.
The lens may or may not move with it. This last point is again a
possible application for panoramic photography.
The function of the against-the sun/light-camera is in general
1. To let in
information of low light intensity without interfering
influences from irrelevant sources in the object space. This is
achieved by means of a slitter screen system which forms a
number of parallel beams which are combined through the
object-lens to form a strip image of relatively high light
2. To let in
information of high light intensity without interfering with low
light intensity information already recorded or yet to be
recorded. This is achieved by means of a co-moving screen - and
the slit which is present in it - , which stops excessive stray
light from an overexposed object. Also internal reflections are
thus during the scanning minimized.
It is clear from the examples and technical drawings shown, that
for example a combination of two such cameras working at a
relative angle-preferable 90° can produce very much of all
the desired information. Certainly when the 'scanning' is of a
very narrow nature and besides, the possibilities to adapt the
photosensitive material, are used.
Furthermore, this new principle of admitting information to the
optical system and the synchronized screening of the
photosensitive material can mean substantial greater
possibilities for various optical systems.
This is so compared to the generally applied coating of lens
Besides that, this principle may be of application in
areas which concern areas of different wave-lengths, also
areas for other spectra!
With the use of TV-cameras with quick moving shutter systems of
this type, it should be possible to obtain information against a
background of full sun or more usually into spotlights without
problems. Low light intensity information can electronically be
raised at will, and possibly computer controlled, while the too
high light intensity information can be toned down, if not
automatically replaced by a neutral information spot.
Here we can see many areas of applications.
Regarding the notion of "aberration in colors in the
light-spectrum" I would like to make the following remark.
This is, in my opinion, for the most part to be blamed on
internal reflections in the lens system. With the use of the
integrated shutter this fault decreases remarkably and even, if
so disturbing, with the application of filters it can be much