What are the differences between a camera with an optical low-pass filter and one without?

Most cameras on the market have a built-in low-pass filter to help eliminate a moire effect. Moire can be seen when photographing a subject with very fine, repetitive details; such as textile fabric.

Although a low-pass filter cannot always eliminate moire completely, the filter is helpful at reducing it. While this is a benefit in most circumstances, when doing landscape photography a low-pass filter may cause a slight loss of detail.

Some high end cameras do not have a low-pass filter installed. The benefit of this is that the image sensor can work to its fullest potential, providing full resolution with clear and extremely realistic detail for landscape photography.