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  #1  
Old September 5th, 2011, 08:18 AM
Carsten Wolff Carsten Wolff is offline
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Default 5x7" underwater

First pics of and with my "Scheimpflug enabled" 5x7" (2 exp) or 6x17cm (4exp) underwater p&s LF camera.









The first two are a bit dark and mysterious, but it was late in the day and the only flash I had with me ended up on that camera :) I'm writing an article on these exploits which I was going to submit to a well known LF magazine shortly, so more details some other time.

Last edited by Asher Kelman; January 14th, 2012 at 02:08 PM.
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  #2  
Old September 5th, 2011, 08:27 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Carsten Wolff View Post
First pics of and with my "Scheimpflug enabled" 5x7" (2 exp) or 6x17cm (4exp) underwater p&s LF camera.






The first two are a bit dark and mysterious, but it was late in the day and the only flash I had with me ended up on that camera :)
Hi Carsten,

Cool project, it allows to still get some DOF even when using wide apertures. Since light is limited, that can be very helpful. Do you also have focus capability, or is it set for a fixed distance?

Cheers,
Bart
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Last edited by Asher Kelman; January 14th, 2012 at 02:10 PM.
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  #3  
Old September 5th, 2011, 08:34 AM
Carsten Wolff Carsten Wolff is offline
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Originally Posted by Bart_van_der_Wolf View Post
Hi Carsten,

Cool project, it allows to still get some DOF even when using wide apertures. Since light is limited, that can be very helpful. Do you also have focus capability, or is it set for a fixed distance?

Cheers,
Bart
It starts off at the fixed hyperfocal distance of 3ft, i.e. 1.5ft. to infinity stopped down, then the Scheimpflug tilt can kick in and I can get focus from the front of the camera plane along the entire seafloor. Conversely I can limit/highlight objects in focus.
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Old September 5th, 2011, 09:10 AM
Asher Kelman Asher Kelman is offline
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Originally Posted by Carsten Wolff View Post
It starts off at the fixed hyperfocal distance of 3ft, i.e. 1.5ft. to infinity stopped down, then the Scheimpflug tilt can kick in and I can get focus from the front of the camera plane along the entire seafloor. Conversely I can limit/highlight objects in focus.
Carsten,

You had an idea and already skills in diving and knowledge using a LF camera. Few actually carry them through like this. Kudos! Could you add to the thread the story behind this fascinating project! Lots of folk have great ideas?

Asher
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  #5  
Old September 5th, 2011, 10:31 AM
Doug Kerr Doug Kerr is online now
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Hi Asher,
Quote:
Originally Posted by Bart_van_der_Wolf View Post
Do you also have focus capability, or is it set for a fixed distance?
Note that to fulfill both Scheimpflug criteria, we must have two degrees of freedom of the lens. We often (imprecisely) characterize the "second" degree of freedom as "focus", but of course it is not to a specific distance (fixed or otherwise), since (as a result of our exercise of the first Scheimpflug degree of freedom) the plane of object focus is in general not perpendicular to the line of sight.

Of course, the two degrees of freedom together (in a complicated way) establish the location and orientation of the "plane" of proper object focus. So both movements (often one exercised by tilting the lensboard and the second by moving the front standard along the bed*) can be thought of, equally aptly, as "focusing" the camera.
*And of course travel along the bed may not be parallel to the aiming axis, as when we have a drop-bed camera.
This is all explained in detail in my technical article, "The Scheimpflug Principles", available here:

http://dougkerr.net/Pumpkin#Scheimpflug


Best regards,

Doug
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  #6  
Old September 5th, 2011, 05:18 PM
Carsten Wolff Carsten Wolff is offline
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Carsten,

You had an idea and already skills in diving and knowledge using a LF camera. Few actually carry them through like this. Kudos! Could you add to the thread the story behind this fascinating project! Lots of folk have great ideas?

Asher
Thanks so much, Asher,
Ok I'll just give you a run-down as to how and why it all came about without going into too much detail for now:

Premise:
I had been using large format cameras for over 10 years and done UW photography for almost three decades. In my previous job, a request for mural-sized, very high resolution, unstitched uw images for a public display came up. This coincided with me contemplating why uw-photography basically stops at medium format. Creative advantages, albeit offset by the many disadvantages the large format brings drove my interest. Wanting to get reasonably close to one's subject whilst maintaining critical focus and a decent depth-of-field is usually not a trivial matter in LF, least underwater. I could elaborate, but to cut a long story short: Lens tilt/back tilt and known height of the camera above the substrate were some of the parameters needed to maximise large format DOF across the sea-life on the seafloor, if subjects in the water-column could be neglected.

Built:
I had most of the parts lying about (old aluminium pressure tanks, 5x7 holders, Canham 617 back, 30-odd LF lenses to choose from, domeports, etc.) and access to some engineering workshops, so cost-wise it wasn't going to be an exorbitant excercise, but it still took a fair bit of thinking about it before it all came together. As tilting a lens behind a fixed domeport would have added complication, I decided on basically just tilting the port with the lens. The camera ended up working rather well off the block (minus one relatively minor initial leak, which led to an o-ring position redesign), but I am still making the camera a bit better.

Operation:
To keep things simple underwater, this camera is basically a 3-trick pony:
a) For maximum depth of field across the seafloor, the camera needs to be positioned at a fixed distance off the ground and the body, film back and lens tilted to a specific degree.
b) in standard position (e.g. parallel lens and film-plane), DOF is limited and can be used as a creative tool; backward tilt is also possible.
c) changing the lens (before the dive) turns it into an excellent LF macro camera. The reproduction ratio is fixed at about 1:2.5 for now.

Issues:
Triggering the press-shutter is done electrically at the moment just through a geared micro-motor and a remote-cable and 12V battery pack; I couldn't find a small, but strong enough solenoid. An R/C servo would have worked better, but I was in a hurry.
I have to open the camera in total darkness due to the lack of darkslides, but a modified changing bag does the job when needed.
The aperture is fixed at the moment. I only control the shutter speed via lens gears, but since I want to maximise DOF and I don't have a ground glass, f22 is fine by me anyway. Adding a geared aperture control is rather trivial, I just don't need it at the moment and I wanted to have a simplified "proof of concept" camera working before I added further functionality.
I haven't tried handheld wreck photography, or such yet, as the camera wasn't designed for that; it is more or less an uw "landscape" - tripod based - camera.

Interesting possibilities:
E.g. by using an ND filter, or working in twilight, or at night, everything that is moving (seaweeds, fish, etc) gets blurred out of the picture altogether or becomes a haze due to the extended exposure time. I, or an assistant can just swim along and, using strong (noosed) underwater strobes on poles can then flash individual subjects back into the picture. Multi-exposures in-camera are of course also an option.
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  #7  
Old January 9th, 2012, 03:10 AM
Dawid Loubser Dawid Loubser is offline
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Carsten, you are mad in the best possible way. Immensely interesting, you can be proud!
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Old January 13th, 2012, 02:21 AM
Carsten Wolff Carsten Wolff is offline
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Quote:
Originally Posted by Dawid Loubser View Post
Carsten, you are mad in the best possible way. Immensely interesting, you can be proud!
Thanks, Dawid; and may I say: What a compliment :)
- Building something like this and then being able to use its capabilities in the way I intended are of course two separate issues...but I already have some nice results, it is a work-in-progress and the whole - admittedly somewhat escapist - project has been tremendous fun so far.
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Old March 21st, 2012, 05:09 AM
Carsten Wolff Carsten Wolff is offline
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Originally Posted by Doug Kerr View Post
Hi Asher,

Note that to fulfill both Scheimpflug criteria, we must have two degrees of freedom of the lens. We often (imprecisely) characterize the "second" degree of freedom as "focus", but of course it is not to a specific distance (fixed or otherwise), since (as a result of our exercise of the first Scheimpflug degree of freedom) the plane of object focus is in general not perpendicular to the line of sight.

Of course, the two degrees of freedom together (in a complicated way) establish the location and orientation of the "plane" of proper object focus. So both movements (often one exercised by tilting the lensboard and the second by moving the front standard along the bed*) can be thought of, equally aptly, as "focusing" the camera.
*And of course travel along the bed may not be parallel to the aiming axis, as when we have a drop-bed camera.
This is all explained in detail in my technical article, "The Scheimpflug Principles", available here:

http://dougkerr.net/Pumpkin#Scheimpflug


Best regards,

Doug
Thank you, Doug,
A late reply by me but you did make an important point about the two degrees of freedom. To achieve this, the camera is set at a certain height and angle, leading to an established degree of lens tilt and thus I have a limit of a single plane of object focus and camera height for a given lens. My approximation and premise is that my object plane, e.g. the seafloor, is level and even, to the degree necessary.

Note:
Practical and diving limitations are such that I try to avoid front standard movements beyond tilt.
In that respect it is a "Two Show Pony" and perhaps a bit crude and limited - and that was the intention. Restricting myself thus makes this a viable and in the end rather successful set-up nevertheless.
The other option is that I can alter tilt to zero to a fixed distance, ordinary DOF camera, or make deliberate OOF shots using e.g. backwards tilts.
Using a 5x7 DD holder I can get two pictures/dive (e.g. one colour, one b/w), or use the 6x17 back for panoramas.
After this winter's hiatus, I have been planning a few excursions for the next few months. I'm looking forward to making some more - hopefully interesting - images.
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  #10  
Old March 21st, 2012, 09:01 AM
Asher Kelman Asher Kelman is offline
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Carsten,

Can you fix the links on the first 2 pictures. These are treasures not to be missed.

Thanks,

Asher
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