CYLINDRICAL DIOPTER

[dusariez <dusariez.pano.optic@xxxxxxxxx>]

Request from Michel DUSARIEZ

A IAPP Memnber from Paris, Mr. Jacques MONTEIL visit me in Brussels and ask
me the following question, is anybody having some experience in that field
to help us.

The project is to put an HORIZON 202 in a cylindrical underwater housing in
order to take of course underwater panoramic pictures.

The HORIZON is model 202 with 28mm lens.
The cylinder is in plexiglass with a interior diametre of 147mm and 163
exterior.

As you know I have personnally made an 360 degrees and more in underwater
some years ago, but with a flat diopter water/air.

Hereunder at the end of this message is the part of the report with the
focal lenght problem I have encounter.

I have no experience with cylindrical diopter WATER/AIR.

If anybody in the list have some experience with a similar problem, please
will them contact me.

I have a 155K jepg image of the cylindrical underwater housing ready to be
send on request.

Thanks in advance for any comments.

Michel DUSARIEZ


>>>>>>>>>>>>>>>>>I have since 1987 built several types of rotating
panoptical cameras to cover 360° and more horizontically in one single
continuous take, which are simpler and  perform better than systems
commercially available.

First an interchangeable back which transforms a normal SLR camera into a
panoptical 360° CAMERA. Then - according to the principle invented by the
Dane Lars R. Larsen, a panoptical camera covering 360° horizontically and
104° vertically on 120 film, two panoptical 360° pocket cameras, and
finally two 360° panoptical, stereo 3D cameras, one for 35 mm film, the
other for 120 film. All these cameras have been described in a book of 138
pages, thoroughly illustrated, written in English and still available.

In 1992, I managed a 'World's First' by taking a 360° aerial photograph
sending the camera aloft by kite.

Towards the end of 1994, I got the idea of taking panoptical 360°
under-water photographs,which to the best of my knowledge would be another
'first'.

After some weeks with systems design and construction of the underwater
body which is of the diving bell type, and after a few dry runs, the first
test was made on the 12th of January 1995 in my old diving club.

The camera is a small format panoptical which on dry land covers 360° on
78,5 mm 35 mm film.The underwater body which turns with the camera during
the take is in plexi and ballasted to give zero gravity when submerged. It
is provided with a porthole of mineral glass in front of the lens. The
underwater body is about twice the height of the camera which sits in the
uppermost part. The lower part is totally open to allow for the use of a
tripod.

As the underwater body descends vertically, water will enter from beneath
through theopen lower part. This is not important during my experiments in
the swimming-pool, at limited depths since the underwater body is so tall
that the camera stays dry in its upper part of the body. According to the
law of pressure, however, at 10 meters depth there is a pressure of two
atmospheres. which will compress the air and make the water rise to fill
the body exactly by half. This is still within the limits of the acceptable
as the body has been designed to take this into account. In any case,
external and internal pressure are equal, so there are no problems for the
underwater body. It is easy to compensate for the rise of water and lower
the level by injecting air at the pressure of the working depth. Injection
takes place at the bottom of the body through a small tube. No working
depth limit with this system.

On the way up towards re-surfacing, the air injected in the body expands
and leaves the body under the lower rim.

A system for automatic compensation for increased pressure and rise of
water in the body has left the drawing board and is being built.

As we are dealing with an 'open body' system, it is of course necessary to
keep the body in a vertical position at all times during submersion.

The first test carried out on the 12th January 1995 proved that the system
works perfectly apart from image sharpness.

Since, of course, I have had similar problems during other experiments,
this did not discourage me, and I started looking for the reasons for these
problems.

After an in depth examination of the problem it turned out that whereas on
dry land, sharpness is the same whether you shoot with the naked camera or
through the porthole of the underwater body, the submersion of the camera
system alters the relative focal length of the lens by a factor of 4/3,
something which seriously upset the very functioning of the process.

I had simply forgotten to take this rather evident peculiarity into
consideration.

The panoptical camera works according to a process where the film travels
simultaneously with the rotation of the camera at a rate of 2 times focal
length multiplied by 3.1416. Since the submersion in water transforms the
relative focal length of the camera by the factor 4/3, the length of film
per revolution no longer corresponds to the focal length.

It would have been possible to correct this problem in several ways - build
a new camera, specifically designed for underwater use, - construct a
supplementary cylindric lens to compensate for the different refraction
index of the water, or attach an external mechanical system which makes the
camera turn once every time an amount of film corresponding to 4/3 of a
normal take travels through the camera. The size ratio of the picture
originaly1/5.40 becomes 1/7.60.

It was this latter solution which was adopted for our successful test
carried out on the 16of February 1995. A black and white film and a colour
film were exposed for 10 complete rotation each per 4 and 12 feet deep.

The results of these first experiments were not of a very great
photographic quality, but that was not our objective, we simply wanted, at
this stage, to demonstrate the process.The size of the negative is only
113mm x 15 mm.  Easy improvements will be made in order to increase the
quality. Changing to 120 format would be a big improvement.

A future extension of our sub-marine experiment will be 360° panoptic
photography in 3-D stereo.<<<<<<<<<<<<<<<<<END OF THE REPORT


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  DUSARIEZ Michel
  14, avenue Capitaine Piret, B-1150 BRUSSELS - BELGIUM
  Tel : 32 2 513 21 46 - Fax 32 2 512 68 29
  <dusariez.pano.optic@xxxxxxxxx>
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