page_title: Selenium meter
section_title: Uncoupled meter
hierarchical_section_title: Selenium meter / Types of meters / Match-needle meters / Uncoupled meter
caption_attribution_description: English: A Match-needle meter of the Zenit photocamera.
context_page_description: A selenium meter is a light-measuring instrument based on the photoelectric properties of selenium. The most common use of such light meters is measuring the exposure value for photography. The electric part of such a meter is an electromagnetic measuring instrument which is connected to the anode and cathode of a selenium photo cell that produces more or less electric power when exposed to more or less light. The optical part of such a meter is a window in front of the photo cell's light-sensitive side. The window's surface is usually structured like a honeycomb made of convex lenses. This type of window helps to bundle the light coming from the direction in which the photo cell is pointed. The mechanical part of a selenium meter is an analog calculator which accepts exposure value and film speed as input parameters for showing the possible aperture and shutter-speed combinations for correct exposure.
context_section_description: The simplest type of match-needle selenium meter shows a clockhand on the meter's scale. This can be moved by turning one slice of the analog calculator. When the clockhand matches the instrument's needle the EV-value is set right on the calculator.
  The picture on the right shows the device of the Zenit - E model, mounted on a left side of the camera. The inner (flat) circle rotates with the help of the knob and sets the film sensitivity (visible in both DIN and ASA units through tiny windows).  The outer circle is coupled to the moving O - shaped marker in the scale on the left and must be rotated till the marker covers the needle (visible in the left corner). The recommended exposures can be read on a side scale against the possible apertures (top scale).  The device is not directly coupled to actual aperture and exposure controls
caption: A match-needle meter of the Zenit.
exif: {"Image ImageDescription": "", "Image Make": "NIKON", "Image Model": "E8400", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "E8400v1.1", "Image DateTime": "2008:12:28 16:30:06", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "216", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "300", "Thumbnail YResolution": "300", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "2128", "Thumbnail JPEGInterchangeFormatLength": "7093", "EXIF ExposureTime": "10/503", "EXIF FNumber": "16/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "50", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2008:12:28 16:30:06", "EXIF DateTimeDigitized": "2008:12:28 16:30:06", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "7", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "14/5", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "81/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3264", "EXIF ExifImageLength": "2448", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "2004", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "32", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}