Before we take a photo we peer through our viewfinder to see what the image will look like before pressing our shutter release button. This is the first function of the viewfinder.
Your viewfinder can have a second function also. It may allow you to focus the image while viewing it. In most cases the viewing system and focusing system go hand in hand.
I will try to relate the different viewing systems to the focus systems they employ.
The Major Viewfinder Systems:
1. Optical viewfinder
2. Single-lens reflex viewfinder
3. Twin-lens reflex viewfinder
4. Ground-glass back
5. Electronic video viewfinder
THE OPTICAL VIEWFINDER
The optical viewfinder is a fairly simple and direct design. It is a simple small glass window, which faces the same direction as your lens. You can find this system on many old point and shoot film cameras and also on some very nice 35mm rangefinder cameras.
An Old Kodak Tourist Camera (Note the viewfinder)
This system does have a major drawback. You cannot focus by looking through the viewfinder. The image you see in the viewfinder will always be in focus. You need some way to focus the image that reaches the film or sensor.
A CLOSER LOOK AT THE VIEWFINDER
Here are three ways the problem is solved by three separate cameras.
1. Fixed Focus
2. Rangefinder
3. Auto-Focus
FIXED FOCUS
The very simple point-and-shoot cameras had instructions, which told you anything more than 5 feet or so away will be in focus, as simple as that. If you try to shoot anything closer than the 5-foot range your image would be out of focus even if it looked in focus through your viewfinder. This is a very limited system indeed.
What we need is a more precise system. We need to gain control of our systems for more creative work.
RANGEFINDER SYSTEM
Rangefinder cameras employ a focusing system that was used on most early 35mm cameras.
Rangefinder use mirrors and levers to link the image reaching the film to the image you see in the viewfinder. If your image is out of focus you see an imperfect image in your viewfinder. Usually it will be an image split across the middle but some systems show a double image similar to ghosting on your TV screen. As long as this image is imperfect you know the image reaching the film is out of focus. Simply turn the barrel of your lens until the image your viewing in the viewfinder is perfect.
Be certain that your Rangefinder is in proper working order. With all the mechanical levers it is easy to have bad linkage to the viewfinder. If your camera is working properly then a clear image in the viewfinder will certainly produce a sharp image on your film.
Parallax error is a common problem with rangefinder systems. This normally occurs when shooting an object close up. I will cover this later.
Last but not least; remember to remove your lens cap. This may seem like a no brainier, but believe me, it’s easy to forget to remove the lens cap when using this type of viewfinder. You will always see a nice bright image, even when your lens cap is on.
The rangefinder system is by no means perfect; this is why the SLR systems became so popular. The SLR solves these problems.
The rangefinder despite it’s limitations remains popular.
Two good reasons:
1. Low-light shooting. The rangefinder displays a much brighter image than an SLR.
2. Rangefinder are much quieter than SLR cameras.
AUTO-FOCUS CAMERAS
I will concentrate on the point-and-shoot cameras. Also known as “idiot boxes”, “goof-proof”, and various other names.
Point-and –shoot cameras use an optical viewfinder, a window that displays the image always in focus. The window will have a target or small aiming device. You simply aim the target at the subject you want to shoot. Computer chips in the camera measure the distance to the subject and instruct tiny motors to move the lens to bring your subject into focus.
Much like the rangefinder camera you don’t see the exact image that is entering your lens. You can’t be certain of the exact image that is reaching the film.
You simply trust the computer to do its job.
SINGLE-LENS REFLEX SLR/DSLR
This system employs a mirror and a prism, which enables you to view your subject directly through the lens.
This system contains a movable mirror placed at a 45-degree angle in front of the film plain or sensor, light entering the lens is reflected by the mirror upward onto ground glass.
Today’s SLR’s employ a five sided prism (a pentaprism). The prism bounces the image around until it is viewed right side up and correct from left to right. Earlier SLR had waist level viewers, which showed the image up right but reversed from left to right.
On almost all SLR’s there is a shutter directly in front of the film or sensor. This shutter is located at the plane of the film or sensor and is called a focal plane shutter. While your looking through your viewfinder the shutter is closed so no light reaches the film or sensor.
The mirror is hinged. When you press your shutter release the mirror snaps up out of the way allowing light to reach the film or sensor. In most cameras the mirror will have an instant return, it will snap back into position as soon as the shutter closes.
A NIKON EL SLR CAMERA
Drawbacks:
1. Blackout – from the instant your photo is shot the viewfinder goes black. Really this isn’t much of a problem with the instant return mirrors. This will only last a fraction of a second or so.
2. Noise- your mirror snaps into position causing a loud slapping sound. This can be a problem when shooting in areas that require extreme quiet.
3. Shudder- believe it or not the mirror slapping into position can cause your camera to shudder. When your shooting at fast speeds this is not a problem. While doing precision work this can cause headaches, especially while using a telephoto lens in low light.
A major problem with SLR viewing occurs while shooting at smaller f/stops. At f/22 only a very small amount of light is able to enter the lens. Since the light entering the lens is dim the image you see in the viewfinder will also be dim. This can make focusing nearly impossible.
A simple fix is to open your lens to its widest aperture, say f/1.8. This allows for the greatest amount of light to enter your lens. Focus your image, then stop down to the f/stop you need, such as f/22 and shoot.
TWIN-LENS REFLEX
The viewfinder on a Twin-Lens Reflex produces an image that is nearly identical to the film image size.
The Twin-Lens Reflex (TLR) has two lenses, one directly above the other. The lower lens transmits the image that strikes the film while the upper lens transmits an image that is for viewing and focusing. The image you view is nearly identical to the image that strikes the film.
Operation: Light passes through the upper lens and strikes a mirror at a 45-degree angle, and is reflected upward onto a horizontal ground glass viewing screen. The image size on the ground glass is the same as the image size on the film. The upper lens is connected to the lower lens via a gear type system. By moving one lens you automatically move the other lens by the same amount. As you focus the image in the viewfinder via the upper lens, you are automatically adjusting the lower lens for perfect focus, so the image reaching your film we be as sharp as the image you view in the finder.
TLR’s use larger film, known as 120 and 220 film. Normal operation of a TLR requires the user to hold it at waist level and look down into the viewfinder. The image you see in the viewfinder is correct from top to bottom, but is reversed from right to left.
Drawbacks:
1. The viewfinder is not as bright as an optical viewfinder or rangefinder.
2. Without a special attachment known as a porro-finder you’re forced to look down into the viewfinder from waist level.
3. Parallax error when photographing close objects.
4. Two lenses are needed instead of one.
5. Limited option on available lenses.
GROUNDGLASS BACK
Groundglass viewing is the system used on studio and view cameras. The entire back of the camera, where the film will be inserted after viewing and focusing, is composed of a sheet of glass which is smooth on one side and ground to a satin like finish on the other.
The image you view on the groundglass will be exactly the same size as the image produced on film. You focus directly on the groundglass.
The image on the groundglass is upside down and reversed from left to right.
The image on the groundglass tends to be rather dim. Most viewfinder used , cover the groundglass and there heard with a hood, or black cloth to cut out any extraneous light. Therefore making the image viewable.
LCD / LIVE VIEW
LCD (Liquid Crystal Display) on your digital SLR camera allows you to view the image on your LCD screen before you actually take the photo.
This is an added bonus. Not only do you have the option of using your viewfinder, now you have a second way to compose your images.
With the image displayed on the screen, composing a photo can become a snap.
Not all DSLR’s are equipped with Live View.
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