I've started to notice a faint darkened circle in my photos. I tried to clean the lenses and I still see it.
What's causing these circles?
Link to imgur album since I don't have enough rep to post images yet. https://i.stack.imgur.com/TzYgG.jpg
- Camera: refurbished Canon EOS Rebel T3
- Lens: EF-S 18-55mm f/3.5-5.6 IS Type II Lens
- Post-processing: None.
Edit: Here's the images.