Nikon D3400 Reference Manual - English - Page 298

5 Raise the mirror. Press the shutter-release button all the way down. The mirror will be raised and the shutter curtain will open, revealing the image sensor. 6 Examine the image sensor. Holding the camera so that light falls on the image sensor, examine the interior of the camera for dust or lint. If no foreign objects are present, proceed to Step 8. 7 Clean the sensor. Remove any dust and lint from the sensor with a blower. Do not use a blower-brush, as the bristles could damage the sensor. Dirt that can not be removed with a blower can only be removed by Nikon-authorized service personnel. Under no circumstances should you touch or wipe the sensor. 8 Turn the camera off. The mirror will return to the down position and the shutter curtain will close. Replace the lens or body cap. 274 Technical Notes