The first form of a device anything similar to the modern camera basic design, was the camera obscura. It was an artists’ tool to help make scale drawings, getting the perspectives right. It had a lens on one plane of a box, with a viewing screen on the opposite plane – very basic. As is the characteristic of all lenses, the camera obscura’s lens created an inverted and mirrored image on the viewing screen. Even before this, it was observed that very tiny holes in a darkened room created an inverted and mirrored image of the outside on to the wall opposite the hole (for example a key hole). This is the basic design of a pin hole camera – and yes, a pin hole acts like a lens. Read on to find out how you can make your own pin hole images on a digital medium.
We’ve understood that a pin hole acts like a lens. What if you could use a pin hole to make an image on your DSLR? It’s really quite simple – you need a camera body cap with a pin hole! It really is that simple. However, the quality of the images that you can make with such an arrangement proves to be far more challenging. Let us systematically look at different aspects of the pin hole picture making process.
Depth of Field
As you can imagine, a pin hole camera does not have a focusing arrangement, and what’s more; neither does it need one. The image created by a pin hole is never totally sharp; it does not have a true focus on any subject near or far from the camera. On the other hand, nothing is comparatively out of focus either. This is definitely one of the advantages of a pin hole lens. To understand this a little better, we need to consider the factors that determine depth of field. Lens focal length, subject distance and aperture are the three defining factors that affect the depth of field created by any lens. With a pin hole lens, the first two factors do not play a part. As for the aperture, if you have studied depth of field even on a basic level, you would already know that the smaller the aperture, the more is the depth of field. Keeping this in mind, it is easy to understand why a pin hole lens creates an infinite depth of field. Let us consider the formula that gives us aperture values –
(f) Aperture = Lens to film or sensor distance / Diameter of lens opening