Seeking info on curving a film plane for pinhole panoramic.

[waynecrider]

Does anyone know of any plans or information around on constructing a curved film plane panoramic MF pinhole camera? Looking to build something 6x12 or larger. TFTH

[bowzart]

Does anyone know of any plans or information around on constructing a curved film plane panoramic MF pinhole camera? Looking to build something 6x12 or larger. TFTH

What are your target parameters?

I don't have exisiting plans because I build my cameras to do what I want them to do. I've done a few. I wouldn't mind participating in a discussion. I am fairly good at explaining how and why things work or don't work, and I'd be interested in learning whatever I can from anyone's project. There are certain problems I would like to solve myself, also.

[patrickjames]

This is just a half a$$ stab, but why not base the radius of the curve of your film plane on the focal length of the pinhole?

[Steve Smith]

why not base the radius of the curve of your film plane on the focal length of the pinhole?

That's what I did for my 6x12 pinhole (which I didn't actually finish!).


Steve.

[bowzart]

There is an inherent problem in wide angle cameras, curved or not. With the radius of the curve being the "focal length" of the hole (I put the f-l in quotes because pinholes don't focus), as suggested, you can eliminate one of the two factors involved in light falloff from the center of the field to the edge, but not both. We're still limited to something less than about 150º angle of view.

These two issues are the falloff of light with distance from the hole and the aspect of the hole as seen from different angles away from the axis. Here's an illustration of the effect of distance: http://www.pbase.com/bullis/image/101371400

The circular field will save about two full stops of falloff.

Think of the aspect as if you look at a coin from straight on (it is round) and then from a slanted angle (it will be compressed). The difference in area between the full and compressed views represents the amount of light lost at the angle you are observing from.

[waynecrider]

This is just a half a$$ stab, but why not base the radius of the curve of your film plane on the focal length of the pinhole?

Actually your right, but others successes or failures are always good information to have. Just curving a piece of wood, (maybe I should use thin opaque plastic), best type of wood to use, cutting the framing, an easy way to make and use a pressure plate, among other facets, go into the whole experience. As others have gone before us to build skyscrapers I look to find experience that will inform me before I plow into this. As it is I think that I may be forging my own way but who knows without asking.


Bowzart I appreciate your interest in discussion. My parameters would preferably be something in the standard wide angle category, say 50 to 60mm on a a format size that would give me 5 exposures on a 120 roll; Basically something between 6x12 and 6x17. I do have an Ansco shutter I can use off an old folder and I was thinking about getting a Lenox Laser pinhole the first time around as it looks to fit the shutter almost perfectly. I have brass to make my own pinhole tho.

I have older unusable folders I can gut if need be for film tensioning springs and parts for winding and film rollers. Next step I believe will be a drawing.

[Joe VanCleave]

Wayne, check out the "Camera Making" section of the F295 forums. Look through the past posts and you'll come up with several curved film plane camera designs.

~Joe

[bowzart]

... I do have an Ansco shutter I can use off an old folder and I was thinking about getting a Lenox Laser pinhole the first time around as it looks to fit the shutter almost perfectly. I have brass to make my own pinhole tho.

I have older unusable folders I can gut if need be for film tensioning springs and parts for winding and film rollers. Next step I believe will be a drawing.

I'd not recommend a laser or any other kind of drilled pinhole for a camera of this type. Any drilling, laser included, makes a tubular hole which will vastly decrease your angle of view and introduce other problems toward the outer parts of the field including very accelerated light falloff. You need the sharpest knife edged pinhole you can make. I make mine starting with .003 pure silver foil through an extended series of "pokings" and thinning by pounding with a polished hammer on a polished anvil. I don't like brass very much because it has limited reworking characteristics. Pure copper is better if you can't find silver, but a jeweler with a rolling mill should be able to provide silver for you. Silver has the added advantage that the hole can be blackened by toning - I use selenium toner for this.

The problem that most interests me right now is how to curve rollfilm with any degree of precision.

L

[waynecrider]

The problem that most interests me right now is how to curve rollfilm with any degree of precision.

I can see using a guide on a router table to cut a channel of whatever width and depth and then cutting off the ends of the routed stock (base and top) for length. Question is material. A jewelry roller could roll metal. Balsa might be bendable enough. In order to get flat film you'd either have to have good tensioning on the film or make two curved film partitions, one with the hole.

[bowzart]

I can see using a guide on a router table to cut a channel of whatever width and depth and then cutting off the ends of the routed stock (base and top) for length. Question is material. A jewelry roller could roll metal. Balsa might be bendable enough. In order to get flat film you'd either have to have good tensioning on the film or make two curved film partitions, one with the hole.

I'm not sure that I have the idea. Do you mean that the edges of the film and backing paper would be riding in slots at top and bottom and some sort of tensioning would be done on the film to keep it tight IN THE CURVE? I wonder. How could that work? Wouldn't the film distort?

Also not sure what you mean by two curved film partitions.

I wonder if the curve could be made by laminating several sheets of veneer held in the curve as the glue dried. I like this idea because it would be rigid, whereas a single piece bent to the curve could quite possibly remember what it was like to be straight.

About the falloff issue. I have successfully produced a half camera on a curve, where the hole is eccentric and slanted, which allows the aspect to correct for the distance hole to film. http://www.pbase.com/bullis/image/101360765

I've not quite given up with trying to figure how to make it a full panorama, but all options seem impossible. So far. I gave the problem for a friend who works as a physicist at NASA. He wanted to motorize the pinhole; otherwise, didn't seem very interested.