Viewfinders, like digital camera LCD monitors, are used to compose and frame a scene. Viewfinders serve another important purpose. While looking through the viewfinder, you can steady the camera by bracing it against your face, making the camera less prone shake.
If your digital camera has a viewfinder, it will be one of two types:
Until recently, the Optical Viewfinder was the most common viewfinder found on digital cameras. But increasingly they have given way to the LCD. Digital Single Lens Reflex camera still have Optical Viewfinders and most now also have a Live View LCD. Generally speaking, Optical Viewfinders work well in both bright and low lighting conditions.
In compact digital cameras, the optical viewfinder shows only about 75-90% of what the camera lens actually sees, not the total area of a shot.
When looking through the eyepiece, there is a center auto focus bracket and parallax correction line at the top. Use the parallax correction line when taking close-up shots.
Optical viewfinders on DSLRs are larger, brighter and show all or almost all of the scene. Some DSLR viewfinders also display shooting information such as shutter speed and aperture.
Electronic Viewfinder (EVF)
An Electronic Viewfinder is a small LCD, typically about 1/2″. While not as clear as an optical viewfinder, an EVF shows the total area of the scene you are photographing, and can be better for taking low light photos if it has the ability to gain up.
An electronic viewfinder also displays key camera settings. The advantage is that you don’t have to take your eye away from the camera to look at the LCD screen for settings and accurate framing.
An electronic viewfinder does have disadvantages: it consumes battery power and it is usually not as bright and clear as an optical viewfinder. In addition, the resolution of some EVFs may not be good enough to focus accurately when using manual mode.
Are viewfinders useless?
Some photographers think viewfinders on compact cameras are useless and, to some degree they have a point as the quality of LCD screens has improved. But others believe having a small viewfinder, even if it’s not so great, is important for times you really need it such as photographing in bright sun or steadying the camera when using a long zoom.
For some high-end digital and mirrorless interchangeable lens cameras with LCDs only, you can purchase a viewfinder as an accessory that attaches externally to the camera.