Have you ever wondered what makes a camera… a camera?
To answer this question, let’s dig into the anatomy of a camera, starting from experiencing the very basic phenomenon at the core of photography: light and darkness connected by a hole.
Camera Obscura And Pinhole Cameras
Imagine you wake up in a dark room. As you move around in the darkness, you see a thin, flickering beam of light entering the room from a small crack in the wall. And then you see it!
On the wall opposite to the crack, a dim yet recognizable image of the outside world. Except it is flipped upside down. What kind of devilry is this?
Well, if there is a natural phenomenon one can experience in everyday life, you can bet ancient Greeks knew about it, and Aristoteles did, in fact, describe what you are seeing some 2400 years ago.
A phenomenon that sits at the very core of photography, and you my friend, are inside a camera obscura.
Now, I could annoy you with a long and tedious description of the physics involved in this, but I won’t. Instead, I want you to stop imagining and experience it for real.
Assuming you don’t want to get trapped in a dark and dusty room with a hole drilled in the wall, here is what you need to do:
- Go grab a large box and seal it so that no light can enter.
- Cut or punch a hole on one side of the box, some 2 cm in diameter.
- On the same side of the box, make a second, smaller hole for you to spy inside the box.
Done. Now, point the side of the box with the holes at a bright outdoor scene and look inside: mind-blowing isn’t it?
Congratulations, you have just created your very own camera obscura, also known as a pinhole camera.
Ok, images are not that good, I admit it, but we can do better. The larger the hole, the blurred and brighter the image is. The smaller the hole, the sharper but darker the image gets.
Here you can find a lot of valuable info on how to craft and improve your own pinhole camera.
Now, this certainly is a fun project to do with the kids, but that’s all it is. To turn a camera obscura into something useful, we need to do better.
What we need is a way to permanently impress the image formed inside the camera on something. For example, the photographic film used in that old camera your grandparents have at home.
Film existed in different formats (medium formats, 35 mm, etc.), in different light sensitivity (labeled according to the ASA or ISO standard), in color, or black and white.
An argent-based emulsion sensitive to light was used to impress the image on the film, which was then developed and the image printed on paper.
You could get rolls containing 6, 12, 24, or 36 frames, and the film needed to be manually advanced from one frame to the next before taking another photo.
Now that we have a way to permanently capture an image with our pinhole camera, we have created a very basic photo camera we could use, for example, to capture a solargraph.
To get sharp images with a pinhole camera, the hole must be rather small, making the image very dim. Even so, eventually you will end up with a white image as you overexpose the film.
To avoid this, we need to stop light from reaching the film after a long enough period of time. In the early days of photography, the photographers would use a clock to time the exposure and manually close the hole.
With the improvement of film sensitivity and camera design, this “long enough” time got as short as a few hundreds of a second or faster. To cope with such short exposures, a mechanical shutter was built into the camera itself.
When you press the button to take a photo, inside the camera, the shutter opens for the desired amount of time before closing shut again, thus stopping exposing the film to light.
Traditionally a shutter is composed of two curtains.
In a “global” shutter, the first curtain opens, exposing the whole frame, and the second one closes at the end of the desired exposure time.
In a rolling shutter, the frame is not exposed as a whole. Instead, the two curtains travel together “scanning” the frame very fast vertically (or horizontally).
With the introduction of the shutter, we can not only control how long the film is exposed to light but also create artistic effects, such as motion blur and intentional camera movement.
This is what is commonly referred to as shutter speed.
As sophisticated as it is now, our pinhole camera still relies on a simple hole to create the image.
To improve on the image quality and the usability of the camera, we need something more: we need a lens.
A simple convex piece of glass in front of the hole will bend and focus on the light rays coming from the scene. This means we can get sharper images even with larger holes, thus allowing for more light to enter the camera.
Modern camera lenses incorporate several improvements over a single convex lens:
- They include several lenses made of specific types of glasses and coating to reduce optical aberration such as chromatic aberrations and coma
- They can have a fixed or variable focal length (prime or zoom lens)
- They replace the fixed hole of a pinhole camera with the diaphragm, a device composed of mobile metal blades that allows you to control the size of the hole, i.e., the lens aperture
- They include a focusing mechanism to let you focus objects in a wide range of distances from the camera, from a few cm up to infinity.
- Depending on the camera, lenses can be fixed to the body or you can have cameras with interchangeable lenses.
With the addition of a lens, we now have a much more sophisticated photo camera in our hands, capable of delivering high-quality images.
Don’t worry, our journey is almost over, but before it ends we need to add just one more thing to our camera.
How do we reliably frame and compose the scene we want to photograph? After all, we can’t look inside our sealed camera anymore, right?
Well, we could aim our camera blindly at the scene and rely on the use of wide-angle lenses ensuring a large field of view and taking advantage of hyperfocal distance to have everything in focus.
This is something street photographers do when shooting “from the hips” to capture candid portraits of random bypassers. But this is far from ideal.
What we need is a viewfinder. This device allows us to frame and compose our image, and it comes in many different types.
One of the most common types of viewfinder is the one you find in a reflex. Behind the lens there is a mirror which reflects the light coming from the lens to a pentaprism. The prism flips the image upright and reflects it back to your eye.
Thanks to the mirror, in the viewfinder you see exactly what your lens sees and precisely focus your lens, rather than rely on hyperfocal distance.
When you take the photo, the mirror flips upwards, the shutter opens, and the light goes to expose the film. At the end of the exposure, the shutter closes, and the mirror flips back in position.
Congratulations, your pinhole camera is now a fully-featured, flexible, and performant modern photo camera.
Digital Cameras: The Present And The Future Of Photography
For more than 150 years, photography has been just that: a bit of chemistry, some physics, and precision mechanisms to improve a box with a hole.
Since 1960, though, electronics have begun revolutionizing the field of photography.
At first, photoresistors (CdS) were used as stand-alone light metering devices to help the photographer correctly set the camera. Shortly after, such devices were built-in into many cameras.
The first self-contained digital camera is credited to an engineer at Kodak and used a CCD sensor, an 8-pound device that gave a black-and-white image of 0.01 megapixels, and appeared in 1975.
Shortly after, the first digital camera based on a CMOS sensor entered the scene and this is the grand grand grandfather of today’s cameras.
Modern digital cameras are essentially a computer, and although the physics behind forming an image is unchanged, digital photography is a game-changer:
- Modern sensors easily outperform film almost every day of the week
- Digital images are “developed” and edited in-camera or via computer software
- Automatization such as Auto Focus and Auto Exposure are now standard in most cameras
- LCD (touch)screen(s) are used to control the camera, review the images, display info and focusing aids and see how the image changes with the camera settings in real-time (live view)
- Mirrorless cameras are now replacing the bulkier and more complicated digital reflex (DSLR)
- Digital shutter are now available
- You can now save on a single card thousands of images
- Today’s photo cameras can also record high-quality digital videos with fast frame rates;
- And many more…
We are at the end of our journey. So, what makes a camera be… a camera?
A sealed box, a hole to let the light come in, a medium sensitive to light to record the image and a few other parts is all you need to make cameras be those high-quality instruments you need to capture forever the most important moments of your lives.
Before you go, here is an interesting similarity to think about: the evolution of the camera closely resembles that of the eye. Intrigued? If so, have a look at this video.