In a viewfinder camera the image in the viewfinder is completely separate from the image acquired through the lens. The viewfinder usually has its own simple lens which shows an approximation of the image that will be captured. Viewfinder cameras are a more simple construction and therefore easier to manufacture than SLR cameras, making them popular in the low-budget market. However there is also a place for viewfinder cameras in the professional arena.
The difference between the viewfinder image and the lens image is known as parallax error. In most cases the difference is small enough that it's not a problem, but it becomes especially noticeable in close-up photographs. High-end viewfinder cameras can compensate for this error and may be linked to the lens by a device called a coupled rangefinder which helps with focus.
Advantages of the viewfinder camera:
- Simple viewfinder cameras are cheap.
- There are fewer moving parts, so less chance of equipment failure.
- Higher light levels to the viewfinder.
- High-quality rangefinder cameras provide excellent focusing, especially in low light.
- Quieter operation than SLR cameras.
Disadvantages of the viewfinder camera:
- Parallax error (unless compensated for).
- The viewfinder image may be quite small.
For most budding photographers the viewfinder camera is not the best choice. Unless you have a specific reason to use this type of camera, you are probably better off looking at an SLR camera.