|Make sure that you are not videoing directly into the sun.|
Set the camera to a high quality setting. Many video formats use compression technologies. The more one compresses the video, the smaller the final file size. Whilst small files are generally good for the web, they are not necessarily good for viewing and can be very blurry or jumpy. The reason is that, compression reduces video quality when it is replayed.
Avoid settings that say things like email. Generally, they compress a video too much. Transfer your video to your computer and view it yourself first. Jerky or jumpy video movements could lose marks in a dressage competition.
Make sure that you set the light settings so they are compatible with the weather conditions.