Standard images shown in galleries are 1000 x 1500 pixels and have a watermark applied to them (if configured). If you want people to be able to download higher resolution images which do NOT have a watermark for free you can enable that on the Event Page under the Event heading.
If Free High Res Images is set to 'No', well there won't be free high res (simple right?).
If it is set to 'Yes' then mypics galleries will give users the option to download the normal watermarked image or the unwatermarked high-res image.