Dust is the enemy!  Dust has been a problem that has followed me for many years.  You battle keeping it off your lens or filter when taking the image and that is for digital or film cameras. 

In the film days you had to be careful that you didn't get dust inside the camera or it would scratch every roll of film. One of my original film cameras is guilty of the one piece of dust that scratches the film.  In the darkroom printing days you had to dust the negative before putting it in the enlarger or you ended up with dust (white) spots on your prints.  Fixing dust spots on prints wasn't too fun as you pretty much had to paint the spots with special dye.

As things progressed but still not digital camera days you would scan the negatives so you could work on them in Photoshop. I have been using Photoshop since 1997 if that give you an idea of the time line. Instead of painting the dust spots you could retouch them out with the computer.   This image is an example of dust from scanning.  I am out of canned air so more dust was on the negative than the norm but you get the idea.  See all the white specks and such!

Now in digital camera days the dust is internal for me.  I am not one of the people who switches lenses so the dust I get on my images is caused by the inner workings of camera.  That dust ends up on the camera sensor and causes black blobs all over the place and is most noticed in images that have the sky in it.  See this image for an example of image sensor dust from my last photo trip.  Usually I just take it out in the computer and put off having the camera cleaned but this last trip the dust has won so I finally took it in for a good cleaning.  So much less processing time if I don't have to spend time fixing dust. 

All red circles are to show some of the dark dust spots.