To address the wide dynamic range of features on the sun,
it is sometimes necessary to combine two images, one short
exposure and one long exposure, into what is known as a composite
image. The overexposed regions from the long exposure are
replaced with those properly exposed from the shorter exposure.
In addition, all optical instruments have a natural 'blurring'
or point-spread function. A composite image is particularly
amenable to removal of the point-spread function of the instrument.
This is done by a mathematical process called deconvolution.