Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/~levay/color/scaling.pdf Дата изменения: Wed Oct 27 23:51:00 2004 Дата индексирования: Tue Oct 2 06:36:16 2012 Кодировка:

Image scaling renders maximum visible detail
Full data range Black: -207 White: 16143
Automatically setting the smallest image value to be black and the highest value to white can force important areas of the image to be rendered invisible. By selecting a minimum and maximum data value to render as black and white, repsectively, (clipping) the significant regions of the image can be made visible. Clipping the bright end to a lower pixel value shows some detail, but fainter details still may not visible. Clipping to still lower levels brings out fainter details but "saturates" (forces larger areas to be white) the bright regions. Applying a non-linear (log, square root, etc.) transformation can compress the dynamic range so that more detail becomes visible. Fainter details can become visible without saturating the brihgtest regions.

Clipped Black: 0 White: 60 0

Clipped Black: 0 White: 150

Logarithmic scale Black: 5 White: 550

Histograms­plots of the numbers of pixels at each brightness value, showing the relative distribution of intensities­can be useful to guide the selection of clipping and intensity scaling. A flatter histogram reflects more detail visible in all intensity levels. Intense peaks indicate a concentration of values at a particular brightness.

R136 (30 Doradus), F555W (V), WF2 HST · WFPC2