A-Photo Mag

The camera obscura was a tool used by artists and painters of yesteryear, to accurately recreate the perspectives of a landscape, on paper. This device was very much similar in design to the basic camera. In fact it would be more apt to say that this is what evolved into the camera as we know it. It is a good learning experience to build one for yourself, to see how a lens creates an image.

You will need

1. A lens
2. A cardboard box
3. Semi transparent paper

Step One

Get yourself a lens. In fact you could take one out of an ordinary magnifying glass. Use a cheap one, its all you need. On the cardboard box, make a hole in the center of one of the sides, and affix the lens in it with glue or cello tape. Remove the plane of the box that is opposite to the lens plane. PS – Something like a show box would do fine for this project.

Step Two

You need to work out the  focal length of the lens. Point the lens (fixed in your box) towards a distance light source such as an overhead lamp or bulb. Use semi transparent paper to figure out the focal length of the lens. Do this simply by moving the paper plane towards and away from the lens plane. You would do well to affix the paper onto a cardboard frame of appropriate measurements, for this ‘focusing’ exercise. Fix the paper when the image is clear. You don’t really need to measure the focal length. On the other end, if the focal length of the lens used is already available to you, that would make matters much simpler. Simply fix the paper at a distance of the lens focal length, measured from the lens (lens plane i.e. The ‘front’ of the show box).

The semi transparent paper

Why we use semi-transparent paper is to allow a bit of light to pass through it. If this wasn’t the case, you would not be able to see the image from behind the camera obscura. Ground glass would be the most suitable material. However, for this simple home project you could use tracing paper, or even ordinary paper that has been coated with any variety of oil to make it semi-transparent.

The Learnings

Use the camera obscura to learn how a lens makes an image. Most people are surprised to see an upside down and mirrored image on paper, but that is exactly how your film or sensor sees it. When you shoot film, the mirror image is simply reversed during printing, and digital cameras have the inbuilt electronics to make the swap. However, high end view cameras require one to work with inverted images. For those about to start shooting large format, using a camera obscura can train the eyes to compose with inverted images. Use different ‘aperures’ of the lens by attaching cardboard rings to its surface. You’ll soon know how aperture affects depth of field and exposure.