# making a camera obscura with inverted image



## harriet

hello

am making a camera obscura in a shed.

does anyone have any ideas about inverting a wall based hole image? i was thinking about pentaprism or a makeshift pentamirror, does anyone have any thoughts, advice or experience?

thanks


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## Bifurcator

You're making a dark room?  And you want to do what?


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## Steph

Bifurcator said:


> You're making a dark room? And you want to do what?


 
A camera obscura is a dark room with a small hole in a wall, which is going to produce an upside down image of the outside world (a bit like a pinhole camera). I think the OP is asking ways to get the image the right way up.


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## Helen B

They often have a lens and mirror arrangement in a little turret in the roof, so the image is projected downwards onto a table, and viewed the right way up.

Where the projection is from a hole (with or without lens) in one wall onto an opposite wall, as in this case, it is more difficult to arrange for an erect image. The image is naturally vertically inverted (upside down), but because you are looking at it from the 'wrong side' it is correct in terms of left and right when viewed from inside the room (laterally correct).

You could project an erect (ie up is up) image with one lens and three front-surface mirrors, in a vertical arrangement, that is also laterally correct when viewed from inside the room. I'll sketch an option out later if I get the chance: first mirror is above a lens (the optical axis of the lens is vertical) sending the incoming rays downwards to the lens, second is below the lens sending the rays upwards to the third mirror that turns the rays towards the wall.

Best,
Helen


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## Bifurcator

Wow, a pinhole camera the size of an entire shed.   Kewl!  What's the purpose?


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## Helen B

Well you could do it with an aircraft hangar.

Another link.

From her other posts I guess that she wants to make large prints directly inside the camera obscura. Most of the time the reversed nature of the print is accepted (ie when the print is turned the right way up it gets laterally reversed).

  Best,
  Helen


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## harriet

helen- to clarify i want to make it a live experience with the hole in the wall- so people are inside the shed which is why i want to invert it-  a sketch would be great of your written idea if possible- is this like the pentamirror? can i give an email address?

thanks for the hangar link- amazing stuff


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## tasman

My front door does this through the peep hole. I see an image of the house next door projected on the wall and it is right side up. So you might want to try it.


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## windrivermaiden

our window blinds do as well, the little holes in the top act as lens. I never thought that multiple holes would work and the room doesnt have to even be that dark. It is so cool.


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## Paul pinhole

Helen B said:


> They often have a lens and mirror arrangement in a little turret in the roof, so the image is projected downwards onto a table, and viewed the right way up.
> 
> Where the projection is from a hole (with or without lens) in one wall onto an opposite wall, as in this case, it is more difficult to arrange for an erect image. The image is naturally vertically inverted (upside down), but because you are looking at it from the 'wrong side' it is correct in terms of left and right when viewed from inside the room (laterally correct).
> 
> You could project an erect (ie up is up) image with one lens and three front-surface mirrors, in a vertical arrangement, that is also laterally correct when viewed from inside the room. I'll sketch an option out later if I get the chance: first mirror is above a lens (the optical axis of the lens is vertical) sending the incoming rays downwards to the lens, second is below the lens sending the rays upwards to the third mirror that turns the rays towards the wall.
> 
> Best,
> Helen


HelenI run a photo charity in the UK Teaching children photography and i am looking to turn a classroom into a camera obscurer but want to show both aspects by the image being inverted and i want to be able to create an image the right way up. I found this thread and saw you was giving advice on how to do this with mirrors. I would really appreciate your help on the if you could and have time. I know you told a member you was going to do a drawing / sketch did you ever get around to doing that? looking forward to hearing back from you Paul


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## compur

Helen hasn't posted here in several years.


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## Paul pinhole

compur said:


> Helen hasn't posted here in several years.


Thank you for letting me know > do you think its worth reposting the question?


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## compur

Maybe a PM to her via this forum would reach her. Just a guess.


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## Dave442

I would think that showing the inverted image would benefit the learning experience at that level. It would be more difficult to explain how the image was corrected so that it was no longer inverted - and if the students didn't see it inverted they would have no reason to ask why the image is displayed right side up.


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