In previous episodes, it is established that Clark Kent and Chloe Sullivan have known each other for years. However, in this episode, Clark states they met in 8th grade. Given that they're both Freshman this season they would have known each other for just one year.
When Lana Lang and Clark Kent are talking at the Torch, Lana tells him that he won't have a future in journalism. This is a reference to the older Clark that will work at the Daily Planet as a journalist.
The episodes title come from the term "camera obscura" which literally means "darkened chamber". It is the term used to describe early devices for projecting an image on a screen, using either a lens or pinhole. In this episode, Lana Lang develops the ability to see through the eyes of Deputy Watts; her vision appears much like a pinhole camera.
This marks the first episode where we hear the sound bullets make when they bounce off Clark Kent's chest.
When Lana Lang goes up to Clark Kent's loft to talk about her visions of Chloe Sullivan, Clark is so desperate to find Chloe that he's consulting a Magic 8-ball. Neither of the characters mention it, but you can see him shaking it and checking it a few times during the scene.