Professional photographers carry a few types of filters with them for a variety of situations.
The Canon Rebel XTi is a mid-level DSLR camera. It offers the benefits of a DSLR, such as interchangeable lenses, while avoiding the high price tag of more advanced models. This camera uses the EF and EF-S lens series by Canon, which are capable of having filters attached to them. A photo filter is a thin piece of glass or plastic that attaches to the lens to alter the light that enters the camera. For the XTi, any filter that has a 58mm thread count can be screwed onto the end of any compatible lens.
UV Filters
UV filters eliminate ultra violet light from entering the camera. The human eye cannot see the light in this range, so removing it allows the camera to have more dynamic range. This filter is often used by professionals to reduce the amount of haze in a photo and to act as a protective layer for the actual camera lens.
Polarizing Filters
This filter type is the most popular among photographers. Polarizing filters eliminate light rays that are oriented at certain angles. The result is generally a photo with richer colors and more contrast. In addition, this lens can be used to remove glare from certain transparent surfaces, such as water, to see directly through them.
ND Filters
An ND filter, which stands for neutral density, is a filter that reduces the amount of light that enters the camera by one or more stops. Essentially, it acts like a tinted window on a car. This is useful on especially bright days where reducing other settings, such as shutter speed or aperture, will change an element of the photo undesirably, like removing an intentional blur. Attaching an ND filter will reduce the exposure, but allow you to keep your settings the same.
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