taking a picture out in bright sun with the second hand 6x7 pentax macro lens that arrived from Japan and I suddenly notice something inside the lens.
I had heard of lens fungus and now I see it. It is often found in older lenses and needs to be treated or it can eventually even etch the glass.
I ordered a tool to help me disassemble lenses, but I decided to go back to a professional who did an awesome job on my Nex 5 sensor some years back. He cleared it for $75 and the lens is just perfect now! The seller sold me a very good lens for a low price due to the fungus and so it was still a bargain!
The professional of fototech explained that as long as the fungus is still white you can eliminate it, but once it acquires color, it's etching into the glass and if you don't act immediately, your lens is forfeit!
Now that I know what to look for I spotted the beginning of fungus in the "life size" adapter that came with it so I will have a go at cleaning that when my tool arrives.
Note: the big white circles are the sun reflecting on the surfaces of the lens... the actual contamination is much less noticeable and getting the sun straight on was the only way you could see it at all.