I was up and about shooting the blue sky, dead trees and electrical lines with the Pentax K-7 in rural Borneo several months back when, to my horror, I noticed an ugly spot on each of the pictures I had taken (see one of them below).
I took out the lens and peered inside the camera and saw the problem. It was not dust particle as I suspected earlier but the remain of what could have been a tiny droplet. It must have gotten there while I was cleaning the lens and the camera body the day before.
There was downpour and howling wind at that time and the window was open. The droplet must have been blown through the open window and shot straight into the sensor surface and evaporated, leaving a stain.
Lesson number one: never clean the interior of your camera near an open window during heavy rain.
I got the stain removed at a camera repair shop and paid RM50 (US$15) for the job. From then on, I swear I’ll be more careful.
There are many ways you can protect camera sensor from dusts. One of them is by way of pledging.

