Re: cylindrical diopter.

["Mitchell P. Warner" <indepth@xxxxxxxxxxxxxxxx>]

Michel,

I've fwd'd your request to Ike of Ikelite underwater housings.  He may be
able to help.

mitch warner



At 11:02 AM 6/30/99 +0200, you wrote:
>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
>
>--------------------------------------------------------------------
>  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>
>  http://users.skynet.be/dusariez/
>--------------------------------------------------------------------
>
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>
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