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| Adaptation at the microscope |
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Optimum use of the brightness differences contained in the image and an ideal signal-to-noise ratio require the brightness range which can be recorded by the electronic sensor to be controlled as well as possible.
No areas in the image should be lost in "white spots" because of overexposure, and dark spots should not be so dark that the structures contained in them are lost because of noise.
The exposure time is set by the digital camera or determined by the connected image recording software. Manual readjustment is normally not required when the subject features a well-balanced mixture of bright and dark areas. If there is a marked imbalance between bright and dark image areas, the exposure time must be prolonged or reduced accordingly, since otherwise image interference can be caused. High-quality systems provide the possibility of limiting the exposure metering area from full-frame metering to so-called spot metering.
White balance: depending on what light source is used, the light used for the exposure features a specific wavelength distribution which can be recognized by a specific color of the light: in the case of a low lamp voltage, the light has reddish hues, while the hue produced by a high lamp voltage is more bluish.
The white balance aims at ensuring a color-neutral image background in the case of different illumination intensities.
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