To assure fine photo results, Canon employs dust-resistant materials and structures to dramatically reduce dust generation within the EOS 400D DIGITAL. Measures also are taken to prevent dust from adhering to the sensor due to static electricity. A remarkable new function is the Self Cleaning Sensor Unit that actually vibrates the low-pass filter to remove dust particles from it. Additionally, by targeting image data for leftover dust after cleaning, the Dust Delete Function within the bundled software can be used after shooting to remove dust spots that may remain on the captured image. For photos that are consistently distinct and clear, this dust reduction system is essential.
		Unwanted shadows on photos can be caused by dust that isn’t actually on the sensor but on the low-pass filter (LPF) in front of it. Though cleaning can be manually selected by menu, automatic cleaning by ultrasonic vibration of the LPF is activated for about one second when the power is turned on or off. As shooting priority occurs on start-up, pressing the shutter button disables the self-cleaning operation and returns the camera to shooting mode. Dust falling off the filter during cleaning adheres to the sticky material of the retaining component at the LPF base.