This can make editing the original objects very difficult. Raster graphics are usually created in a manner similar to painting, where you stroke colors onto a canvas. These strokes change the colors of the pixels that are under the brush. Scanned photos, 3D Renderings, Adobe Photoshop, Painter, and Macromedia XRES files are examples of raster graphics. Raster graphics tend to take up much more space than similar vector graphics because each pixel must be stored.
Large images can result in very large file sizes.
Notice that it appears smoother around the edges than the same size vector image. This is because most raster images are anti-aliased which is a smoothing process. The resolution seems to decrease. Since all that is stored in the image are the pixels in the grid, all the computer can do when you zoom in is to magnify those pixels. This is referred to as resolution dependent.