Ghost photo, or not?
Taking photos of ghosts is not as easy as it seems. Some people have a 'knack' of being in the right place at the right time, some people are sensitive and instinctively know where to aim, and some people just don't get anything at all.
Everyone (and I mean everyone) will get photos of what at first glimpse may seem to be caused by supernatural means but turns out to be something natural. These photos are called 'false positives'.
We're not saying that all images that can't be explained are actual spirits, beings or other paranormal phenomena - no one can! However there might just be a chance that you might (either intentionally or by accident) capture something that cannot be explained!
If you are in doubt of what you see in your photo:
Go back to the location, take note of the surroundings. E.g., if you see a strange ball of light in your photo, go back to the location in daylight - perhaps you will see a inconspicuous light off in the distance that you didn't notice!
Make use of photo imaging software and make the image lighter - this might help you to see the surroundings much easier (see below).
Most of all use your own judgment!
Film verses Digital Cameras
There is much debate on whether or not digital cameras should or should not be used to capture evidence of paranormal activity.
Digital Cameras are prone to picking up more than film cameras, such as dust or light flare - however for the same reason, they are also believed to be more likely to capture paranormal anomalies due to the electrical capture of images.
Why is this so? Well, spirits are meant to be made up of electrical energy (which is why they can affect electrical equipment such as TVs, Radios etc, so easily!).
Of course, the problem with digital photos is:
1) They do not have a negative -- so they cannot be proven to be real, or fake.
2) They (or digital scans of actual photos) can be easily altered with photo imaging software.