Inventors and innovators come forwardgreenspun.com : LUSENET : Large format photography : One Thread
Dear all, when writing on the Gilde camera I thought of asking all inventors and innovators to come forward with their products so that more genius(I guess the correct plural is Genii) or geniuses will come forward. please do and show us what your mind and hands have produced!
-- Andrea Milano (firstname.lastname@example.org), February 12, 2001
Over the past two years, I've been intermittently working on a design for a pressurized bellows that should 1) help prevent vignetting with extreme movements by forcing the bellows outward at all times, and 2) force the film flat against its pressure plate. So far, so good, but since I perceive very little market demand for such a thing, it's not a high priority hence the slow progress to date (here in Arizona, the number of rainy days we get each year is fairly small...).
-- Jeffrey Goggin (email@example.com), February 12, 2001.
Perhaps a genius or innovator or experienced designer could use this idea. I've been wondering whether some of the techniques used in building ultralight canoes (and kayaks, I assume) could be used to make a hybrid wood-composite camera that was lighter than traditional wood cameras, and stronger as well.
I am referring to the use of fiberglass, Kevlar and other materials, either by themselves or laminated with some other material, and bonded with a resin in a vacuum.
Wood is a nice material to work with, and looks good, but it is hygroscopic and changes dimensionally as the humidity changes (if only slightly). What is more, the joints tend to be weaker than the material itself.
My father-in-law, a retired engineer and whitewater canoe racer informs me that canoes used in Olympic whitewater slalom racing use this technology, and so do the most advanced (and expensive) flatwater boats used in racing and touring. However, the technology is apparently not taken as far as it could be.
I'd like to build my own view camera, but I wonder about the availability of such parts as a rack & pinion for focusing (and frankly, the project seems intimidating. Tho I just bought a lathe I'm no machinist, and am only a fair to middlin' weekend wood warrior.)
-- Erec Grim (firstname.lastname@example.org), February 12, 2001.
Although I didn't mention it in my previous post, I have been playing around with composites, too. The tough part is making tubes but I've found a cheap solution for that: Buy a center post for one of Gitzo's CF tripods! I had previously bought a piece of CF tube that was used to make an accessory car part but picked up one of the Gitzo posts as soon as I saw my friend's new 1228 tripod. Food for thought...
-- Jeffrey Goggin (email@example.com), February 12, 2001.
I'm working on an autofocus/autoexposure 4x5 sheet film camera. The trick is to make the autofocus system work with tilts of the lens board. I have three linear motors driving the lens board which is enough to move the board back and forth along the rail and to tilt and swing. I have a high resolution CCD array at the film plane. I segment the image area and perform 2-D fast Fourier transforms (FFT) on each segment and use the results to identify the nature of the blurring and what needs to be done to correct. I then use a generalized MINIMAX algorithm to find an optimum solution. Unfortunately, the MINIMAX routine finds a local minimum, and I'm wrestling with how to find the global solution. (For example, my Maxxum 9 has three autofocus sensors. Say an object 5 feet away is centered on the left sensor, and an object 20 feet away is centered on the right - which one does is focus on? [Of course, my autoLF camera can bring them both in focus, but I'm giving a simplified example of the problem. In the camera-with-movements case, the problem is determining which plane to focus.]) I may leave it to the photographer to get kind of close to what he wants and let the system "fine tune" the focus. But I imagine every autofocus designer wrestles with this problem. I don't know how my Minolta decides which sensor to use or which object to focus on. Well, that's the big problem. I'm also performing trades on how many and what size segments I should take to divide up the screen.
The camera does do pretty good now of bringing the ground right into focus from near to far.
At the moment, the whole thing is driven by my Sun workstation, but I don't see anything that would prevent the algorithms from being implemented in a microcontroller should the camera go into production.
The CCD array also finds the darkest and lightest areas in the image and performs the exposure analysis to ensure good exposure every time. The computer also returns the required gamma (CI, or whatever you want to call it) so I know how to develop the image. I guess eventually I could add an electronic shutter, but haven't bothered with that yet.
I'm also thinking about an "autowind" (autoload-unload?) for sheet film, but haven't gotten too far with that, yet. I like to take photos of rocket launches down here, and would like to get more than one a launch, but those things just don't wait around for me to inser slide, remove holder, flip holder, reinsert holder, remove slide, recock, etc., etc., so I want to automate it. I like the big, sharp negatives on my 4x5, but miss the 5.5 fps of my Minolta (oh - and autobracketing would be a natural next step - getting the correct exposure for a rocket launch is a crap shoot.)
Basically, I don't see why people who need or want autofocus and perfect exposure should be denied the advantages of large format such as movements and the large negative size!
-- John H. Henderson (firstname.lastname@example.org), February 13, 2001.
I just finished building a prototype sheet film day light tank that doesn't use the inversion technique. It's advantage is a smaller amount of developer required per sheet, and absolutely no streaking or uneven development. Great for PMK Pyro developers (One other person has used this technique so far and found it gave them good results as well).
After that it's on to a better archival washer - it's on the drawing board right now and I have about 1/2 the material needed.
-- doug mcfarland (email@example.com), February 13, 2001.
I came up with a cheap, alternative focussing system other than a rack & pinion or helix, for a 4x5 point & shoot camera. I have a rough description of it at http://job.webstar.nl/cam3pg.html
-- Julian Bell (firstname.lastname@example.org), February 14, 2001.