CS194-26 Project2: Building a Pinhole Camera
Yao Fu, cs194-26-aen
Borong Zhang, cs194-26-agb
In this project, we built a pinhole camera using a dark box with a pinhole on one face and a piece of white paper on the opposite side. As the light goes into the box from the pinhole, the corresponding image (but inverted) will form on the white paper and we used a camera with long exposure time to record this image.
Our dark box is made from a 30cm*30cm*30cm box. We cut two holes on the selected face: the smaller one for the pinhole and the larger one for our camera. Then, we lined the opposite face with a piece of white paper (printing paper) and covered all of the rest of the faces with black paper. We also bought black tape and glue stick in order that the color of the tape does not influence the color of the wall. Then, we seal the box carefully with card paper and thick tapes to keep it as dark as possible. Actually, at the very beginning, while we did not realize that our box is not sealed well, we got the images below: too much light comes in and the box is too bright inside.
Here are the images we got:
scene1: 5 mm
scene1: 2.4 mm
scene1: 0.8 mm, iso 1600
scene1: 0.8 mm, iso 3200
We can see that while we use 5mm, the result is quite blurry and bright for that too much light comes into the box and the big hole also results in more serious scattering of light.
Thus, while using 5mm pinholes, we have to adjust the exposure time to 15s (the shortest) and lower the ISO to about 100-400 (depends on the whether condition). The 2.4mm pinhole works quite will, the image is still blur but a lot better than with 5mm because and pinhole size is smaller thus less light comes in. Intuitively, the same principle should also be applied if we decrease the diameter again. However, when we first changed the pinhole size to 0.8mm, the image we got is totally dark using the previous setting because the light gathered in the box is not enough and it's hard to be captured by the camera. Thus we must extend the exposure time to 30s and higher the ISO value to 800, 1600, or even 3200 (depends on the whether condition). After adjusting the setting, we got pictures with the highest quality (sharpest) among the three pinhole sizes, still darker than the 2.4mm one though. The situation remains the same when we moved on to the next scene.
Then we made some small pieces of aluminum foil and cut holes on each of them with different diameters. According to the formula on the project webpage, the approximated most appropriate diameter should be 1.9*sqrt(550*300*(10)**(-6)) = 0.77mm. Therefore, we chose these sizes: 0.77mm, 2.4mm, 5mm, and used them separately.
Here are additional 4 images we captured with the 0.8mm pinhole
Bells and Whistles
For the light painting one, we first tried to use an iPhone and it’s quite easy to control.
Then we proceed to use our dark box to do the same job. However, this one is much harder. We kept practicing for some time and in the end, we got the pictures below. We named some of them so they looks like real "painting" instead of scribbling. Names always have magic like this...
thunderstorm on sea
Interestingly, it appears that if the light is strong enough and we adjust the angle between the bottom face of the box and the ground, then make the hole facing the direction of the sun(but not facing the sun directly, otherwise we will only capture a bright white image of the sun itself), then it’s possible that we would see a bright light spot and it’s emitting light.
We also utilize the property of long exposure to make interesting images like the followings.
Just set the exposure time to 20s and the same people can keep still for 10s in two different places.
stability vs movement