URGENT!!!

aaronmichael

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I've been helping a friend of mine build a 12 foot square room out in the desert to be a camera obscure as the final project. The house is facing another house that is run down. We're almost done building it but I need some information on pinhole size and material. I've built camera obscuras before and pinhole cameras and generally use soda can metal to make my pinholes out of. However, for his application, the aperture is going to need to be like half an inch in diameter? What would be the best material for him to use? I would think it would be a little difficult making a larger hole in something as thin and flexible as soda can metal. I know that the thinner the material is, the better the image quality, and of course the less reflective it is the better. Also, seeing as he is showing the house on Saturday, the material needs to be readily available at home depot, or a hobby shop,...etc. Any information would be greatly appreciated!
 

marenmcgowan

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Ok, you don't need to hear from me because I can't help...but, I just have to say that sounds like an awesome project! I'm sure someone will be along shortly who knows what's up!
 
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aaronmichael

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marenmcgowan said:
Ok, you don't need to hear from me because I can't help...but, I just have to say that sounds like an awesome project! I'm sure someone will be along shortly who knows what's up!
Click to expand...

Hahaha, thanks! With his permission, I'll post some photographs of the house once it's built.
 

JBrunner

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A flat black painted fender washer should do the trick. Probably thin enough when you think of it as scaled to the camera. If you really want it thinner than that, get some sheet brass from a hobby shop and drill the appropriate hole in it, and hit it with the flat black can.

http://shop.hobbylobby.com/products/-015-brass-sheet-106617/
 
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aaronmichael

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Ah, a washer! Such a good idea, thank you! I think you're right in regards to material thickness in reference to the size of the room. Would you be able to suggest any types of thin woods that would work well?
 

ME Super

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Lauan (I hope I spelled that right) comes in 4ft x 8ft sheets and is about 1/4 inch thick and would probably work well, unless it's to go on the outside of your camera obscura. For that I would say 1/2 inch plywood.
 

FM2N

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If the film will be on one wall that is 12 feet away from where the pinhole will be placed the pinhole size will have to be 2.5mm. The opening of a small thin washer may work. Sounds like trip to hardware store with ruler. The f/stop would be 1434
If film will be closer let me know and I will re-figure size and f/stop
 

FM2N

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Since it says you are a large format shooter I would think that taking the front and rear cells out of one of your lenses and the closing the aperture to the right size would be the best way to go. I am sure that like most of us you have a shutter that is broken for speed but the aperture still is able to be set. I would think that f/22 is probably around 2.5mm.
Drill hole size of rear of shutter, keep it tight and push shutter in set aperture and you are ready to go.
 

Worker 11811

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Why not use a sheet of roofing tin? Spray paint it flat black.

If the metal is thin enough, you can use a spade bit to drill the hole. It's not optimial but it will work if you don't run the drill too fast.

If you want to make a clean hole that doesn't need to be filed, use a round panel punch. You can get them at Harbor Freight, etc., for cheap.
 

JBrunner

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That is a pretty clever idea.
 

lxdude

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The pinhole diameter for a twelve foot (144 inch) focal length, according to the online calculator, is 2.55mm. In inch size, the diameter is .100" (1/10 inch).

Much smaller than a half inch.

Soda can material will work fine for a hole that size. Flatten it well. Or get some thin brass at a hobby shop. To make it easy to mount, you can drill it, then glue the material to a piece of wood or metal (like a washer, for example) with a larger hole.

A 2.5mm drill is undersize by only .001 inch. In inch size, a #39 drill (.0995") is even closer.
Use whichever one you can find. The Dremel section at a hobby shop or possibly even a hardware store might be your best bet to find individual drill bits in that small a size.
 
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DWThomas

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You could clamp a piece of sheet metal between two pieces of plywood or other flat stock and drill through the whole sandwich to minimize tearing up the edges of the hole. (Drilling through relatively thin metal that isn't well anchored can get quite exciting!)
 

TheToadMen

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You could make a larger opening and add a frame to put aperture cards in it.
Types like these: http://re-inventedphotoequip.com/Site/Configurations.html
Maybe Reinhold (the lens builder from this website) can make you a card with a smaller aperture.
Or just make one yourself from wood with a shim in it.
This way you can adjust your pinhole size easily if you want to make the focal distance smaller.
Projecting the whole image on the back wall or making a print with photo paper at 1 or 2 feet from the pinhole or ...
You could even add a red filter to position the photo paper before making the actual print.
Use Duct tape on the outside as a shutter ;-)
 

mark

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I turned my classroom into a camera obscura one year. I used a piece of copper flashing for the hole, drilled it between two pieces of scrap boards as has been mentions then ran a debur tool around the inside. I did not have the right size hole but it was close enough. We sat in the dark for a while and as the kids' eyes got accustomed to the lack of light they got more and more excited as they watched cars drive past upside down and backwards.

Have fun
 

Jim Jones

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Using PinholeDesigner with a user constant of 1.4 (determined by empirical testing for optimum on-axis sharpness) I get a pinhole diameter of about 2mm. We rarely agree on the perfect formula for determining pinhole diameter; that's part of the magic of pinhole photography. A slightly larger pinhole will favor sharpness towards the image corners. With such a large project, a little experimenting is wise. Pinholes that large are easily drilled between sheets of hardboard, hardwood, or even plywood, as Dave recommends. A larger drill or a countersink can debur the relatively thick material that is appropriate for such a long focal length. I used the end of an ordinary tin can for the pinhole in a solar eclipse camera about 24 feet long.
 
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