Stairway Camera

[csalem]

Okay, this is a question for lens nuts and unusualists. Let's see if I can describe the situation: There is a 'floating' stairway up to my apartment(building owned by me). Two of the risers (kickers) have one inch holes punched in them. They kind of look like someone was making a birdhouse then used the wood for the stairs instead. Behind the stairs is a door that opens onto the backyard. On these sunny days when the door is open the holes project fuzzy images of the backyard and my neighbors house onto the wall facing the stairs. Very cool discovered pinhole camera.

So here's the issue. I want sharper and brighter images. Obviously I can get either by sacrificing the other through narrowing or opening the bird-holes, but I want both and I think the answer is a lens.

I want something that is cheap and durable. My only thought is a glass coke-bottle bottom. Any suggestions?

Obviously, I'm not looking for leica-sharp images, just sharper without sacrificing light. Oh, and I can drill out the holes wider.

[ROL]

Very cool project. I think you need to find transparent media, glass or plastic, through which you can develop the requisite focal length to get a discernible image on the wall.

...then you need to explain to your visiting neighbor, just how that doesn't make you a "peeper". But then I'm only a nut and unusualist, not lens specified.

[Erik Gould]

Check out surplus shed or Edmond scientific. They often have single element optics in long focal lengths. You won't have the wide angle of a pure pinhole however. I have an 8' camera obscura so I've had a little experience with this kind of thing. I see accidental pinhole images all the time now. It's pretty fun. Good luck!

[Maris Rusis]

Long focal length lenses are easy to synthesise. Get two eyeglass blanks, say +3 dioptres and -3 dioptres, put them together and the powers cancel: the focal length is infinite. Separate the lenses by 1cm and a positive power appears corresponding to a focal length of 11metres. A 2cm separation delivers about 5m FL; and so on. Adjust as required. Gullstrand's Equation deals with the numbers.

[csalem]

Long focal length lenses are easy to synthesise. Get two eyeglass blanks, say +3 dioptres and -3 dioptres, put them together and the powers cancel: the focal length is infinite. Separate the lenses by 1cm and a positive power appears corresponding to a focal length of 11metres. A 2cm separation delivers about 5m FL; and so on. Adjust as required. Gullstrand's Equation deals with the numbers.

thanks, this sounds like a promising possibility.

[Bruce Watson]

Long focal length lenses are easy to synthesise. Get two eyeglass blanks, say +3 dioptres and -3 dioptres, put them together and the powers cancel: the focal length is infinite. Separate the lenses by 1cm and a positive power appears corresponding to a focal length of 11metres. A 2cm separation delivers about 5m FL; and so on. Adjust as required. Gullstrand's Equation deals with the numbers.

What Maris said.

Consider mounting the two lenses in cardboard tubes, one a little larger than the other. Then you can focus by sliding the tubes apart to increase separation of the lenses. When you find the right distance, gaffer tape the two tubes together at the seam. This will make it light tight-ish and lock focus for you. If you like it and want to make it permanent, this is an easy way to measure lens separation at the correct focus point. Then you'll be able to hit the wood shop and make a simple mount for the lenses.

[csalem]

Good suggestion. Edmund scientific has some cheap lenses for 10$. I'm also going to talk to my local optician about lens blanks. I'll use a set-up like you describe. When I get something in place I'm take a picture and post it.

What Maris said.

Consider mounting the two lenses in cardboard tubes, one a little larger than the other. Then you can focus by sliding the tubes apart to increase separation of the lenses. When you find the right distance, gaffer tape the two tubes together at the seam. This will make it light tight-ish and lock focus for you. If you like it and want to make it permanent, this is an easy way to measure lens separation at the correct focus point. Then you'll be able to hit the wood shop and make a simple mount for the lenses.

[dant]

Maybe I can help You improve this image before buying lens. Few weeks ago we have pinehole workshop in out city and one of the things that was mentioned was that hole edge must by very thin to give sharp image. So after calculating optimal hole size for hole-to-wall distance You can cut it from paper/cardboard and tape it to existing hole in wall. I may not give you lens quality, but can give nice effect before You will find suitable glass.

[Randy]

I purchased a 25mm lens with a focal length of 54" from surplus shed a year or so ago and mounted it in sheet of plywood and mounted it over my bathroom window so I can enjoy the front yard as I am sitting of the toilet I first used a pinhole but it took to long for my eyes to adjust to the faint light. By the time they did, I was done.

Here is a picture of what I see every morning. It is inverted so you can see the towel rack is upside down...and you can see the wall paper pattern.



I have also purchased a lens with a F/L of about 8 feet but have no experimented with it yet.

[Michael Graves]

I purchased a 25mm lens with a focal length of 54" from surplus shed a year or so ago and mounted it in sheet of plywood and mounted it over my bathroom window so I can enjoy the front yard as I am sitting of the toilet I first used a pinhole but it took to long for my eyes to adjust to the faint light. By the time they did, I was done.

Here is a picture of what I see every morning. It is inverted so you can see the towel rack is upside down...and you can see the wall paper pattern.



I have also purchased a lens with a F/L of about 8 feet but have no experimented with it yet.

Do people know you're staring at them while you're taking a s....while you're taking care of personal business?