Фотоаппараттың қарау терезесі: түрлері мен қағидалары

System through which the photographer looks to compose and focus the picture

In photography, a viewfinder is a small window the photographer looks through to see what a photo will look like before they capture it. Some viewfinders see directly through the lens, whereas others are separate and show an approximation of what the photo will look like. The second type is much simpler to design, but creates a parallax effect because the viewing angle is slightly different between the finder and the lens. The first type avoids this parallax effect, and is commonly used in SLRs which use a complex mirror system to direct light from the lens to either the film or the viewfinder. Viewfinders are used in many cameras of different types: still and movie, film, analog and digital. Some cameras, such as camera phones and mirrorless cameras, do not have viewfinders and display the image preview on a larger screen. Although some mirrorless cameras do have an electronic viewfinder, where a small screen shows a video feed from the image sensor.

Twin lens reflex (TLR) cameras had a large lens above the taking lens, and a large mirror at 45°, projecting an image onto a ground glass screen viewable from above, with the camera at waist level. The viewfinder lens was of similar size and focal length to the taking lens, though the optical quality was less critical; the mirror was of similar size to the film. These cameras were relatively expensive; the Rolleiflex and cheaper sister Rolleicord were the pioneers. Both single and twin lens reflexes allowed focussing by adjusting the lens until the image was sharp.

Single lens reflex (SLR) cameras viewed the scene through the taking lens. Early SLRs were plate cameras, with a mechanism to insert a mirror between the lens and the film which reflected the light upwards, where it could be seen at waist level on a ground glass screen. When ready to take the picture, the mirror was pivoted out of the way (without moving the camera). Later SLRs had a mechanism which flipped the mirror out of the way when the shutter button was pressed, followed immediately by the shutter opening. Instead of a waist level arrangement, a prism was used to allow the camera to be held to the eye. The big advantage of the SLR was that any lens, or other optical device, could be used; the viewfinder always showed exactly the image that would be projected onto the film. The live preview feature of digital cameras share this advantage of the SLR, as they also show the image exactly as it will be recorded, with no additional optics or parallax error.

Viewfinders can be optical or electronic. An optical viewfinder is simply a reversed telescope mounted to see what the camera will see. Its drawbacks are many, but it also has advantages; it consumes no power, it does not wash out in sunlight, and it has "full resolution" (i. e. the resolution of the photographer's eye). An electronic viewfinder (EVF) is a CRT, LCD or OLED based display device. In addition to its primary purpose, an electronic viewfinder can be used to replay previously captured material, and as an on screen display to browse through menus. A still camera's optical viewfinder typically has one or more small supplementary LED displays surrounding the view of the scene. On a film camera, these displays show shooting information such as the shutter speed and aperture and, for autofocus cameras, provide an indication that the image is correctly focussed. Digital still cameras will typically also display information such as the current ISO setting and the number of remaining shots which can be taken in a burst. Another display which overlays the view of the scene is often provided. It typically shows the location and state of the camera's provided auto focus points. This overlay can also provide lines or a grid which assist in picture composition. It is not uncommon for a camera to have two viewfinders. For example, a digital still camera may have an optical viewfinder and an electronic one. The latter can be used to replay previously captured material, has an on screen display, and can be switched off to save power. A camcorder may have two viewfinders, both electronic. The first is viewed through a magnifying eyepiece, and due to a rubber eyepiece it can be viewed perfectly even in bright light. The second viewfinder would be larger, of a higher resolution, and may be mounted on the side of the camera. Because it consumes more power, a method is often provided to turn it off to save energy. In late 2010, Fujifilm announced hybrid viewfinder of optical viewfinder and electronic viewfinder in one viewfinder for its highend compact cameras. There is a half mirror prism that reflect data from LCD to the optical viewfinder, so we can see both the shooting frame and the shooting data. A button can change the hybrid function to electronical viewfinder by blocking the image through the optical viewfinder with moving a half mirror prism to be a straight up mirror. Some special purpose cameras do not have viewfinders at all. These are, for example, web cameras and video surveillance cameras. They use external monitors as their viewfinders.