Hubble Process Makes Images Viewer-Friendly

As an aerospace scientist who regularly deals with data from space instruments, I found “PR With Universal Appeal” (Sept. 5) to be very misleading. It states that images produced by the Hubble Space Telescope are altered. To say an image is altered, however, presumes that some true image actually exists. The purpose of the Hubble is to produce scientific data, not true-to-life photographs. It is not like a normal camera that reproduces what we see by measuring the three primary colors that the eye is sensitive to.

The Hubble can detect a much larger multitude of spectral bands than those three primaries. These color bands can be mapped arbitrarily to the three primaries in various combinations to produce what is called a false-color image -- a common tool of the trade. A false-color image is useful to scientists because it enhances color contrasts, thus highlighting features that would never be distinguishable to the naked eye. To call these images colorized is absolutely incorrect. “Colorize” means to take a movie originally filmed in black and white and digitally add the three primary colors that were never actually measured by the original film. The Hubble does the opposite: It measures many colors and reduces these to three.

Steve Mills

Glendale