Digital Development (DDP)

DDP is an image processing algorithm which diplays information in a non-linear way. Normally a CCD image is displayed in such a way that the faintest details of an image are visible. However, in doing so very bright portions of an image (e.g. the nucleus of a galaxy, the center of a star cluster, etc) look very over-exposed. Examine the images below:

The top left image shows the very faintest details of the spiral arms of this galaxy (M63). However, the center of the galaxy is just a white blob (very scientific!). It is not saturated, however, so all of the information about the galaxy is still stored in the portion that is displayed as a "blob." The top right image demonstrates this by displaying only the bright portions of the galaxy. Details in the nucleus of the galaxy are seen, but the faint spiral arms are lost. Finally the bottom image shows the result of applying DDP to the image. Now both dim and bright portions can be seen simultaneously. Thus DDP knocks down the intensity of the very brightest details while raising the level of the very faintest. This process is similiar to a digitial form of dodging (from film processing).

Click HERE to see the color image of this galaxy from the same data.

Updated: 8/16/2000