HST doesn't take photographs exactly like a normal camera.
The HST instruments take data which follows a complex path
until it reaches the scientist. Data from the HST instruments
follow a complex path, part of which is the pipeline,
after which they are made available to the scientists. At
this stage, the data are calibrated and put into
a form useable by the scientists' analysis software.
from the cameras consist of numbers whose value represents
brightness measured by each detector in the camera. Raw
data can contain a wider range of values than can be represented
on a display or print. To view the region of interest,
software may be used to change the contrast and brightness,
much like the controls on a TV.