These viewfinders can generally be divided into:
Those that are separate from the lens, commonly known as optical viewfinders
Those that look through the lens, commonly called TTL viewfinders
Electronic viewfinders, also known as eye-level LCD viewfinders
Compared to LCD viewfinders, the first two types of viewfinders have many advantages. First, they help avoid excessive battery drain caused by using the LCD, thereby extending shooting time and battery life. Second, when shooting outdoors, they prevent framing errors due to LCD screen glare. Below, we’ll take a closer look at the differences among these three types of viewfinders:
1. Optical Viewfinder
Regardless of whether the camera lens is fixed-focus or zoom, the optical viewfinder’s framing remains unchanged. It operates independently of the lens, simply mimicking the lens’s angle of view and focal length. Most consumer point-and-shoot cameras (including entry-level digital cameras) use this type of viewfinder.
The size of the viewfinder’s light inlet determines image clarity. For users who wear glasses, having a relatively larger aperture is quite important, because glasses tend to place their eyes farther from the viewfinder, making accurate framing difficult. Some viewfinders now come with diopter adjustment features, allowing photographers to achieve more accurate framing without wearing glasses. However, diopter adjustment is only useful for people with nearsightedness or farsightedness — it’s meaningless for those with normal vision.
Optical viewfinders should be positioned as close as possible to the optical axis center of the lens to reduce parallax. Parallax occurs because the camera lens and the viewfinder view the subject from different positions, resulting in slight differences in what each sees. Generally, optical viewfinders cannot display 100% of the image captured by the lens — usually only about 85% or less. This is why TTL viewfinders were developed.
2. TTL Optical Viewfinder
This type of viewfinder is typically found on more expensive digital cameras and shows the actual image being captured by the lens. Most traditional film cameras have already adopted this viewing method.
Different TTL viewfinder systems work in different ways, and the level of detail they can display varies depending on the specific usage, but all of them achieve framing by reflecting or scattering light that passes through the lens. Therefore, for digital cameras using a TTL optical viewfinder, the image seen on the LCD and through the viewfinder is consistent.
3. Electronic Viewfinder
The advantages of this type of viewfinder are the same as those of a TTL viewfinder: it displays the full scene to be photographed, is visible in daylight, and can show shooting information such as aperture and shutter speed. In addition, it can also display the camera menu — something other viewfinders cannot do.
The disadvantages of electronic viewfinders can be summarized in three points: unlike optical and TTL viewfinders, they require a lot of power; similar to LCD screens, they are prone to glare, which can affect framing accuracy; and compared to optical systems, they appear more coarse. The last point can be quite significant, as such systems cannot display the smallest details within the frame — for example, whether a person’s eyes are open or not.