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The aperture and angle of the light cone must be adjusted (via the size of the diaphragm) for each different objective lens with different numerical apertures. Condensers typically consist of a variable-aperture diaphragm and one or more lenses. Light from the illumination source of the microscope passes through the diaphragm and is focused by ...
The field diaphragm is then partially closed; the edges of the diaphragm should be in the same conjugate image planes as the specimen, therefore should appear in focus. The focus can be adjusted by raising or lowering the condenser lenses and diaphragm. Finally, the field diaphragm is reopened to just beyond the field of view.
The centre of the diaphragm's aperture coincides with the optical axis of the lens system. Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris. See the articles on aperture and f-number for the photographic effect and system of quantification of varying the opening in the ...
A bright-field microscope has many important parts including; the condenser, the objective lens, the ocular lens, the diaphragm, and the aperture. Some other pieces of the microscope that are commonly known are the arm, the head, the illuminator, the base, the stage, the adjusters, and the brightness adjuster.
In optical microscopes a darkfield condenser lens must be used, which directs a cone of light away from the objective lens. To maximize the scattered light-gathering power of the objective lens, oil immersion is used and the numerical aperture (NA) of the objective lens must be less than 1.0. Objective lenses with a higher NA can be used but ...
The condenser may also include other features, such as a diaphragm and/or filters, to manage the quality and intensity of the illumination. For illumination techniques like dark field , phase contrast and differential interference contrast microscopy additional optical components must be precisely aligned in the light path.
Enlarger lens: using the aperture ring, the photographer adjusts the iris diaphragm. The image from the negative or transparency is projected through a lens, typically fitted with an adjustable aperture marked with f/ stops, onto a flat surface bearing the sensitized photographic paper. By adjusting the ratio of distance from film to lens to ...
Aperture settings are usually not continuously variable; instead, the diaphragm has typically 5–10 discrete settings. The normal "full-stop" f-number scale for modern lenses is as follows: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, but many lenses also allow setting it to half-stop or third-stop increments.
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