If you have intrusive dots on your images and it’s annoying or it’s an effort to Photoshop out the dots – it’s time to get the filter cleaned.
 
Most dots will show up in a low contrast image.
 
To test the camera for dust take a picture of a white wall or a blue sky. If there is dust on the filer it will show up with less contrast images and a small aperture
Small aperture - stop down the lens to the highest number on the aperture ring ie: F22.
 
 
 
                   
 
                      Before clean                                 After clean