Everyone is familiar with cameras today. A lot of us know what they do but do not know how they work. Well, I hereby invite you to join me in a four part series in exploring the technology behind smartphone cameras.
We are going to start from scratch and move all the way up from the definition of a camera all the way up to computational photography. Please take note that this is not a typical science geek class but for lay people trying to understand smartphone camera terms in a simple and straightforward manner, so if something is not necessary, we may skip it entirely. It is my hope that by the end of this series, when you see something like this in a smartphone specification:
Quad 48 MP, f/1.8, 26mm (wide), 1/2.0″, 0.8µm, PDAF
8 MP, f/2.2, 13mm (ultrawide), 1/4.0″, 1.12µm
2 MP, f/2.4, (macro)
2 MP, f/2.4, (depth) (Redmi Note 8 quad camera specs)
You would simply smile and know the meaning offhand.
For part one, we are going to examine the following:
2. How a camera works
3. Lens or lenses
4. Aperture and Depth of field
A camera is a device (or part of a device) that helps us to capture images and scenes. If the images are still, we call it photography and if the images are moving, we call it videography.
Like most other items, a camera has parts. The main parts include a lens or lenses, an aperture, a shutter (turns on and turns off the sensor), an image sensor and pixels (or photosites).
2. HOW A CAMERA WORKS
A camera works just like the human eye. For a person to see, light from the sun bounces off an object and then enters the eyes. At the back of the eyes, there are cells that are sensitive to light called rods (for black and white vision) and cones (for colour vision). These rods and cones catch the light that enters the eyes and forms an image. This image formed is sent to the brain for processing and interpretation.
This is why when you go out of your house at night with your brain half asleep, a sudden breeze can make the white dress that is hanging outside look like a spirit, after your initial panic you calm down and take a proper look, your brain will then give you a proper interpretation of what you have seen.
The same thing happens here. When you want to take a picture and you activate the camera app, an electronic shutter turns on the image sensor at the back of the camera. The light from the object you want to snap passes through the air into the aperture, through the lens and hits the image sensor. The sensor captures the image and the shutter turns it off. The sensor then sends this captured image to the phone’s processor for image processing in a place called the Image Signal Processor (ISP). When this is done, the finished product appears on your screen.
A lens is a piece of optical glass that allows light to be focused at a particular point. The job of the lens is to collect light from the outside and focus it on the sensor. The thickness of a lens can be measured in millimeters (mm), this thickness is also called it’s focal length. The thicker the lens, the smaller its angle of view, the thinner the lens, the wider its angle of view. A 20mm will capture a wider area than a 50mm lens.
There are many types of lenses used for photography e.g. wide angle, ultra-wide, depth, normal, telephoto, time of flight etc. Popular lens manufacturers include Leica and Carl Zeiss.
4. APERTURE and DEPTH OF FIELD
The aperture is simply the hole or the opening in front of the lens where light passes through.
Depth of field is simply the area in a photo that stays sharp while the other parts blur out. Simply put, when you take a picture, sometimes, the centre stays sharp and edges are blurred. The area that stays sharp is called the depth of field.
The size of an aperture plays a huge part on how much depth of field that a camera can perceive. The depth of field relative to the aperture size is measured in F stops. F stop numbers are inverse in value. This means that, the smaller the number, the larger the aperture. So this means that a camera with an f stop value of F/4 has a wider opening than a camera of F/11. The wider the aperture, the more light enters the camera but this reduces it’s depth of field.
The Depth of field is also affected by the distance between an object and the camera. The closer you get, the smaller (or shallower) your depth of field. This is especially important for taking close ups as well as focusing. The sensor size is also important too, the smaller the sensor, the wider the depth of field. The type of lens used also matters. Wide angle lenses with shorter focal lengths have a wider depth of field when compared to a telephoto lens with a longer focal length.
And this brings me to the end of the part 1 of “Let’s talk Cameras”, I hope I was able to to break this down for you. If you find anything confusing do leave a comment below and I will explain better to you. Thank you for reading.