One of the most overlooked and taken for granted items on your DSLR is the viewfinder.
That’s right, the viewfinder – the little rectangle on top of your camera. While your DSLR will get an overhaul from model to model with new and improved specs, the little viewfinder stays the same. But it’s your eye to the world and the origin of your creativity. What you frame up in the viewfinder is the image – and memory – that you will be taking home. Looking through the viewfinder helps you stabilize the camera better. Additionally, when using the viewfinder you will have the camera braced against your body with your arms tucked in (instead of outstretched), which adds up to taking sharper images.
The two main types of viewfinders are pentaprisms and pentamirrors. A pentaprism, found on professional-grade DSLRs, uses a prism to redirect the light from the lens to the viewfinder. Pentaprisms are a higher quality than pentamirrors, which redirect the light through a series of mirrors. Pentaprisms provide a brighter image in the viewfinder than pentamirrors. Pentamirrors are generally found on entry-level DSLRs and are constructed of plastic (instead of glass) because it is cheaper to mass produce.
Viewfinders can be either optical or electronic. DSLRs have an optical TTL (through the lens) viewfinder, which allows you to look through the lens and see precisely what the lens projects onto the sensor. (Sometimes on compact cameras, the viewfinder is parallel to the camera’s lens so that what you see is different from what the lens projects onto the sensor.) Optical viewfinders do not consume any power. Electronic or digital viewfinders are usually the LCD (liquid crystal display) screen on the back of the DSLR. The LCD screen can be used to review photos or video footage and also displays the camera’s menus, features and functions. Some digital compact cameras have an LCD that can pop out and swivel to accommodate various shooting angles. But when there is bright sun outdoors and you can’t see the image on the LCD, it’s the optical viewfinder that comes to the rescue.
For photographers who wear glasses, the optical viewfinder also has a diopter. The diopter acts in the same way as eyeglasses to correct your vision and bring everything in focus. The diopter can help you dial in the focus and get a sharp image with or without your glasses. Diopters can be in the eyepiece or snap or slide on. Most diopters have a standard correction ranging from -3 to +1. To adjust your diopter, focus the camera on an object and look through the viewfinder. Adjust the diopter until what you are seeing is sharp. Another way is to look through the viewfinder and make sure your digital readings look in focus.
Viewfinders also have an associated magnification number. When the spec sheet says the viewfinder has a 1X magnification, that means when you look through the viewfinder using a 50mm lens, you will see the same image as you would if you were standing next to your camera and simply using your eyes. The image size will be different depending on the focal length of the lens: wide angle lenses make objects in the foreground appear very large while mid-ground objects appear small and far away. Zoom and telephoto lenses bring objects up close and large.