An Explanation to Visual Evidence:

Ghosts in Photographs

Many people believe that flash photography can bring out spirits because of the infrared in the flash of a camera. This is one of the first methods used in paranormal investigation and is often very effective. However, it is not as effective as video with infrared or audio recorders because many times a photograph will have false positives.

Orbs

Orbs are very debatable pieces of evidence and are often thrown out. Reasons for throwing them out vary due to the many natural occurrences can cause orbs such as: dust, moisture, bugs, and numerous other variables. However, there is that one in a thousand orb that is not explainable, very rarely will an orb be unexplained though.  Credible orbs are said to be energy of a spirit that doesn't have enough energy to fully manifest itself.

Mists

Mists are good evidence of entities, but again, debatable evidence due to the fact that fog, breath, etc. can cause mists or fog just as easily as spirits can. However, a mist is not quite as easy to debunk as an orb, and often are more impressive than orbs.  A credible mist is claimed to be a spirit just before they are manifested, and are not yet a figure but have enough energy to be a mist. 

Apparitions

Apparitions are the least common piece of evidence and are extremely hard to debunk. They are very rare to catch on film, but if are caught they are an extremely good piece of evidence. Apparitions are spirits that manifested themselves into a figure. There are a few different types of apparitions, such as partial apparitions, which could be a shadow of a figure or just part of a figure. There are also full bodied apparitions, which is the full figure showing itself.