Canon PowerShot S120 Manual (en)

Click several times when dust spots are not erased completely
Where unwanted dust spots are not erased even after performing 
step 5 once, they may be erased completely when you click several 
Mainly spots of dust can be erased with the repair function
Spots of dust can be erased with the repair function. You may be 
unable to erase lines of dust. In this case, use the copy stamp 
The dust-erased image can be reverted to its original condition 
at any time
A dust-erased image is displayed or printed as a dust-erased image. 
However, since the dust on the image is not actually erased, you can 
always revert to the original image by clicking the [
] button in 
the Dust Delete/Copy Stamp tool palette or performing the “Re-Editing 
an Image” procedure 
Printing dust-erased images
You can print as a dust-erased image by printing it in DPP.
The image becomes a dust-erased image when converted and 
The dust-erased RAW image actually becomes a dust-erased image 
when converted to a JPEG or TIFF image and saved 
Additional information
For images shot with ISO speed range expansion set, noticeable 
noise may make it difficult to view dust spots in the copy stamp 
window, so using this function is not recommended.