Nikon 25214 D70 User's Guide - Page 204

Technical Notes-Caring for the Camera The Low-Pass Filter The CCD image sensor that acts as the camera's picture element is fitted with a low-pass filter to prevent moiré. Although this filter prevents foreign objects from adhering directly to the image sensor, under certain conditions dirt or dust on the filter may appear in photographs. If you suspect that dirt or dust inside the camera is affecting your photographs, you can check for the presence of foreign objects on the low-pass filter as described below. 1 Remove the lens and turn the camera on. 2 Press the button and select Mirror lockup from the setup menu ( 162). Highlight Yes and press the multi selector to the right. The message, "Press shutter-release button" will be displayed in the camera monitor, and a row of dashes will be displayed in the control panel and viewfinder. Mirror lock-up Yes OK No 3 Press the shutter-release button all the way down. The mirror will be raised and the shutter curtain will open, revealing the low-pass filter, and the row of dashes in the control panel will blink. 4 Holding the camera so that light falls on the low-pass filter, examine the filter for dust or lint. If there are foreign objects on the filter, the filter requires cleaning. See the following section. 194