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low-pass filter

In a dSLR, one or more low-pass filters are located in front of the imaging sensor to: allow the lowest-frequency waves through and cut off the highest, effectively reducing the amount of detail getting through to the sensor, resolve aliasing that causes jagged edges when photographing circular objects and diagonal lines, and to protect the sensor from dust (most have an anti-static coating to discourage dust from sticking).

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low-pass filter

Used with digital imaging, low-pass filters are integrated into many digital sensors to suppress aliasing and moiré.
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