Image Manipulation and Computational Photography

Project 2: Building a Pinhole Camera

Jianglai Zhang, Zheng Shi



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Overview

A camera obscura, or a pinhole camera, is a photo-taking device based on the principles related to the reflection and capturing of light. The light reflecting off an object is directed through a pinhole on one of the facets of a dark box, which hits onto a screen on the opposite side, and finally is captured via a camera shot into the box with long exposure. The camera obscura is easy and fun to make, and gives us amazing results and photo quality despite the simple design and physics principle it relies upon.


Camera Design

The major components in the design of our camera obscura include a DSLR camera with focus lengths 17-40 mm (17mm is used for this project), a shoe box with all internal facets covered by black paper other than one which is covered instead by a piece of white paper as the screen, a exchangeable pinhole device made from black paper so that we can change the aperture easily. On one side of the box, we cut two holes through one of which we can insert the lens of the DSLR that is doing the actual photo taking job and through the other we can align with our pinhole device to adjust the aperture size. One thing to notice is that we've also sealed all edges and corners of the box with duct tape so that no light can get through into the box other than through the pinhole. In addition, we've added some random materials nearby when we shoot simply to ensure better image quality as the hole through which lens comes in may leak light into the box. Here are the designs looked at from outside and inside:


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External-Front

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External-Side

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Internal-Front

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Internal-Back


Image Capture and Analysis

A key factor in the photo shooting is to have a good, sunny weather, since we want more light onto the object we hope to take photo of and eventually captured on the canvas in the box. With that guaranteed, the rest is quite simple. We took two sets of pictures of two different scenes, each sets consisting of three pictures taken with different aperture sizes in its diameter of: 1mm, 3mm, and 5mm (approximatley). While we took the pictures, we also adjust the focal length to diameter of the entrance pupil ratio (F-value of the cameras), the iso, and the exposure time accordingly but without sabotaging the quality and effects of the original images by too much.

Now that the photos are taken, we can observe that with larger sizes of aperture, the brightness of the picture is increased while the quality of it reduced. This is due to that when the aperture gets larger, more light can come through via the pinhole and thus the greater brightness, while at the same time the light can be directed into the box in more different directions and thus more different positions of the same ray will be landed on the canvas, and thus the reduced quality. We observe that three millimeter is quite a proper size of aperture for the environment and weather of our photo taking today. Notice that the tree photo taken with 3mm aperture appears to be brighter than the one taken with 5mm aperture. This is due to that we adjusted the iso and F-value to make the picture more visible but might have over-adjusted the parameters a bit. The two sets of scenes with different aperture sizes are displayed below:


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House-1mm

iso:800, F5.0, exposure:15 sec

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House-3mm

iso:800, F5.0, exposure:15 sec

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House-5mm

iso:800, F5.0, exposure:15 sec

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Tree-1mm

iso:3200, F4.0, exposure:20 sec

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Tree-3mm

iso:3200, F4.0, exposure:20 sec

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Tree-5mm

iso:800, F5.6, exposure:15 sec


Additional Pictures

The selected aperture size for our additional collection is 1mm, which are displayed below:

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Green Wall

iso:3200, F4.0, exposure:20 sec

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Ford Fusion

iso:3200, F4.0, exposure:20 sec

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Mini Cooper

iso:3200, F4.0, exposure:20 sec

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Yellow House

iso:1600, F4.0, exposure:15 sec


Bells and Whistles

Trace Picture: One thing we can do with the long exposure is to use a relatively stronger light source to draw anything we like (this time we used a phone flashlight) by tracing the shape in the air. The pinhole camera will record the trace of light and the results are displayed below:


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Heart

iso:6400, F4.0, exposure:30 sec

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Star

iso:6400, F4.0, exposure:30 sec


Drawings Pictures Combined: Just an idea that we can put small drawings in front of the screen (canvas) so that we can combine it with the picture taken; we think this can be counted as something bells and whistles since this is something special only to the camera obscura but not an actual camera. Note that the drawing needs to be placed upside-down as the images we captured on the screen are upside-down due to the pinhole principle:


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Fight

iso:200, F4.5, exposure:10 sec

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Fight in Production



Credits

Inspiration taken from friends, past projects, python libraries, papers and other online resources.