Unit Two : The Gear
Introduction to Cameras
We’ll start this class with a rather gentle introduction to the technical aspects of photography by asking ourselves what a camera is and what its different components are. Chances are that you will already know some of this, but going through it anyway will at least ensure that we have defined a common vocabulary.
In the strictest sense, a camera is simply a device that can record light. It does so by focusing light on a photosensitive surface. From this simple sentence, we can see the three main parts of any camera.
Dan Cristian Pădureț via UnsplashThe Sensor
The sensor is a photosensitive surface which reacts to light through either a chemical process (film) or an electric one (digital sensor). There are fundamental differences between these two, which we will cover in a subsequent lesson. But for now, we can consider both identical: they are a grid of several million tiny dots (pixels), and each can remember how much light was received in a given period. Each sensor has three important qualities: resolution, size, and what we can call “quality.”
Resolution is simply the number of pixels - it is slightly more complicated with film, let’s not worry about that for now. The more pixels you have, the more fine-grained detail you can theoretically record. Any resolution above 5 or 6 megapixels (millions of pixels) will be enough to display on a screen. Higher resolutions come into play for two important applications: printing and cropping.
To have a good reproduction quality, it is generally estimated that between 240 and 300 pixels should be used for every inch of paper (dots per inch, or dpi). This will give a natural limitation to the biggest size one can print if the print is viewed closely (viewing distance is also an important aspect of resolution for print). For instance, a 6MP image at the dimensions of 2000×3000 pixels can be printed at a maximum size of 12.5×8.3″ at 240dpi (2000/240 = 8.3, 3000/240 = 12.5). Printing bigger by lowering the dpi or artificially increasing the resolution is possible, but this will come at a loss of image quality. Having a higher resolution allows you to print bigger.
Cropping means reducing the size of an image by discarding pixels on the sides. It’s a very useful tool and can often improve composition or remove unwanted elements from an image. However, it will also decrease resolution, since you lose pixels. Therefore, how much cropping you allow yourself will depend on the initial resolution, which you want to be as high as possible. This is also what some cheaper cameras, along with phone cameras, call “digital zoom.” General point of advice is that digital zoom should be avoided, as the same effect can very easily be reproduced in post-processing through cropping.
The physical size of the sensor is very important and will have an impact on many other parameters, most of which we will see in subsequent lessons. These include: field of view (“crop factor”), depth of field, high ISO noise, and dynamic range. Bigger sensors will also allow for more widely spaced pixels (increasing image quality) or more of them (increasing resolution). Bigger is almost always better, and this is one of the main reasons that Digital Single-Lens Reflex cameras (DSLRs), as well as medium format cameras, produce a much better image quality than compact cameras.
Finally, sensor quality is harder to quantify, but it refers to how well the sensor reacts to difficult light conditions. Low light conditions will require an increase in ISO, and will demand a sensor to have as little noise as possible. High contrast conditions will require a good dynamic range to be recorded adequately.
Chelsea London © 2024. iPhone X | Automatic SettingsThe Lens
The lens is the second component of any camera. It is an optical device that takes scattered light rays and focuses them neatly on the sensor. Lenses are often complex, with up to 15 different optical elements serving different roles. The quality of the glass and the precision of the lens will be extremely important in determining how good the final image quality is. Lenses must compromise, and a perfect all-around lens is physically impossible to build for a reasonable budget, weight, and overall size. For this reason, good lenses tend to be specialized and having the ability to switch them on your camera will prove extremely useful.
Lenses usually come with cryptic sequences of symbols and numbers that describe their specifications. Without going into too much detail, let’s review some of their characteristics:
Focal length refers roughly to the “zoom level,” or angle of view, of the lens. We will address this in more detail in the next lesson, as it can be a surprisingly tricky subject. A focal length is usually expressed in millimeters. You should be aware that the resulting field of view actually depends on the size of the camera sensor on which the lens is used - also known as the crop factor. For this reason, we often give “35mm equivalent” focal lengths, which is the focal length that would offer the same view on a 35mm camera (the historic film Single-Lens Reflex format) and allows us to make meaningful comparisons. If there is a single length (e.g. 24mm), the lens doesn’t zoom, and it is commonly referred to as a “prime lens.” If there are two numbers (e.g. 18-55mm), you can use the lens at any focal point within that range. Compact cameras often don’t give focal lengths but simply the range, for instance, 8x. This means that the long end is 8 times longer than the wide one, so the lens could be an 18-144mm, or a 35-280mm, etc.
The aperture is a very important concept which we will talk about in much detail later on. The aperture is an iris in the center of the lens which can close to increasingly small sizes. This action limits the amount of light that hits the sensor. It is referred to as an f-number, and you’ll see it written like f/2.8, for example. To make things more confusing, the smaller the number, the bigger the aperture! For now, don’t worry about this too much. The important number on a lens is the maximum aperture, and generally, the lower the better. Professional zoom lenses often have f/2.8 maximum apertures, and cheaper consumer lenses have ranges such as f/3.5-5.6, meaning that at the wide end, the maximum aperture is f/3.5, and at the long end, it is f/5.6. Aperture can be closed to tiny levels, usually around f/22.
Lenses also need a focusing system. Nowadays, most lenses have an internal motor that can be piloted by the camera - the autofocus. They also have a ring to allow the photographer to focus manually. Lenses are often equipped with stabilization systems (called VR by Nikon, IS by Canon). They detect small movements, usually handshake, and compensate for them by moving the optical elements internally in the opposite direction of the movements. Though not magic, these systems tend to work very well and allow sharp images to be taken at slower shutter speeds. Side note: lens-based stabilization is becoming increasingly less important due to sensor stabilization in modern mirrorless cameras.
Chelsea London © 2024. iPhone X | Automatic SettingsThe Body
Finally, the body is the light tight box connecting the lens to the sensor, and ordering everyone around. Though some film cameras are just light-sealed boxes, most digital cameras are now small computers, sporting all sorts of features. Let’s review some of the components found in most bodies:
The shutter. Think of it as a curtain in front of the sensor. When you press the trigger, the curtain opens exposing the sensor to light from the lens. It then closes again after a very precise amount of time, often a tiny fraction of a second. Most shutters operate between 30 seconds and 1/4000 of a second. That duration (the shutter speed) is one of the three very important exposure factors, along with aperture and ISO (more on those later!). Some cameras lack a physical shutter and will use global or electronic shutter - there are advantages and disadvantages to this.
A light meter. As the name suggests, it measures the quantity of light and sets the exposure accordingly. How much manual control you keep at this stage is one of the most important decisions in photography. There are different metering modes, but except in very specific cases, using the most advanced, most automated one will provide the best results - and make things easier on you!
A focus detector. This is used to drive the autofocus motor in the lens. There are two competing technologies: contrast detection and phase detection. These systems tend to vary greatly between basic and advanced bodies, but it should be noted that they all need reasonable amounts of light to work properly.
A way to store the image just created, and make room for the next. Back in the days of film, this was just a lever to advance the roll to the next unexposed frame. Now, it is a pipeline that ends up in the memory card that the camera is using. If you are shooting JPEG instead of raw (more on this in another lesson), there is an additional stage where the internal computer performs all sorts of black magic on the image to output a ready-to-view JPEG file.
A way to frame. It can be a multitude of things; optical or electronic viewfinder, LCD screen, or even ground glass. DSLRs have an optical viewfinder that allows “through-the-lens” viewing and immediate feedback. Mirrorless, compact cameras, and phones use an electronic viewfinder allowing us to preview the image’s exposure, depth of field, et cetera. Rear LCD screens of cameras have taken significant jumps in usability in recent years and are now a very viable option for framing your images.