House Of People - Pinhole camera

[ValentinBrutaru]

Hi guys and girls!

I’m doing a master programme at an art university in Sweden and I’m planning my final art project.

I’ll be deeply grateful and it will help me a lot if you could give me some advices on this.

Here’s what is it about:

Camera description:

Original from Romania, I want to build in Bucharest a pinhole camera in which people can get in. This camera has to be 5,8m (19ft) high, 9m (29.5ft) length and 8m (26.2ft) width.

Model for Forum.jpg

Photo-paper:

By calculating the wall on which the image will be projected, I will need an area of 52,2m² (561.8ft²) of negative photographic paper.

The photographic paper needs to be the most insensible photo-paper available (I want to expose it, ideally, for ~20 hours).

It can be sold in large rolls or preferably in small size packs ~10 x 15 cm (4 x 6 inch).

Questions:
1. Is it possible to make multiple exposures to the same photo-paper and still have a correct exposure of the image?
(I want that every time a person enters the camera the exposure to start and last for ~5minutes. I expect to have ~200 visitors, so 200 exposures of 5 minutes each = Total:~17Hours exposure)
2. Can you please recommend me a photo-paper that could fit my needs for this project?
3. Can you please recommend me a place where I can buy or get sponsored with the photo-paper described above?


Calculate exposure time:

In my research I have found some information, but nothing very clear and concrete (in any case not for a camera that big).

Is there a way to calculate the hole’s dimension and the exposure time considering the dimensions of the camera and the sensibility of the photo-paper?


Developing process:

I’m planning a week to develop the exposed photo-paper. Please describe the process needed for the photo-paper you recommend. It will help me a lot to identify the appropriate developing process for each photo-paper recommended and will also help me to make tests accordingly.


Thanks a lot for your time and any link, suggestion or comment are very welcomed.

With gratitude,
Valentin

[EdoardoAmbrosio]

I'm new in this forum as you, so probably the least suited to answer so complex questions.
According to my calculations, a focal length of 9 meters requires a 4mm hole, with a record brightness: f/2250.
You don't need a very insensible paper, I guess.
The biggest challenge, in my opinion, is to determine the correct reciprocity chart for a 20 hours exposure. You need the help of a big photo paper company for that more than their sponsorization!
think very carefully about light leaks!
Please write about your progress, your project is very interesting for me!

[ValentinBrutaru]

Hey Edoardo!

Thank you for your input and interest. I will update my discoveries during the research.
If you can write me the formula that you used or a link to it, it will help me to figure out some of the things.

Keep in touch!

[bradjudy]

The trick will be figuring out how to have the light level high enough that people can see something of the image once their eyes adjust to the darkness, but low enough to do the very long exposure you are looking for. While Edoardo is correct that the optimal pinhole size for that distance is around 4mm, I think people will see it as a totally dark room, even after their eyes adjust.

[ValentinBrutaru]

Hey Bradjudy!

Here's an example on 'How to' transform a room in a camera obscura and there is specified that the eyes will adjust in few minutes. https://www.youtube.com/watch?v=yvWX6-0_VHU

I've seen other example also and it seems that it works, but of course I have to make some of my own tests. I intend to build a pinhole camera 58cm x 90cm x 80cm (1:10 scale from the final intended space) and make an isolated view-finder for testing how long it takes for my eyes to get used to the light inside the camera.

Can you please tell me how did you get to the 4mm hole recommended to the pinhole camera I intend to build? I'm interested in formulas or a special calculator, if you know something about that...

Thank you.
Valentin

[EdoardoAmbrosio]

I've just seen the video. Probably you missed the point that they used a lens, not a pinhole. Bradjudy is right, even after five minutes you'll see nothing but a big dark room.
But still I like your project. So, why don't you try with a real lens, as in that video? Give every people entering the room a digital camera, fixed to the right parameter, and tell them to shoot 3 picture of their favourite details. You don't need a huge photo paper and chemicals anymore, just a white wall.
By the way, you can find every practical info about pinhole here:
http://www.mrpinhole.com/

[bradjudy]

As Edoardo mentioned, MrPinhole's site is good and it includes a calculator for optimal pinhole size: http://www.mrpinhole.com/calcpinh.php

The calculator is designed to find the size that creates the best resolution. This might not be the most important thing for your project.

Like many others here, I have done a camera obscura in my own home in the past. Here's an image (already flipped so the image appears upright):



This is with a focal distance of probably 4m and a pinhole about 25mm in diameter, which results in f/144. I tried smaller holes (smallest was probably 6mm which is f/610) and the image was barely visible and appeared to be in black and white (human eyes don't see color when there is very little light).

Experiment with aperture sizes in your space to find what gives you the effect you want for the visitors. Then figure out how that effects your exposure.