After a number of successful years with the x t20 I notice big dark spot on images. Inspected lens and sensor for what the cause is. It is a large visible spot on the sensor. It looks as if it could to hardened oil but not sure. I have ordered a cleaning kit but a few weeks away.
What is the likely source of this stuff? It is not dust so I am assuming oil. I have not changed lenses outside my office, but I recently purchased several used fuji lenses. I tried them all in my office and took each one out and tried it outside. Everything went well until today. I noticed the dark spot on the