Quote:
Originally Posted by h0ughy
this is a genuine question - how do you process your images to get the true colours of a deep space object - especially with a modified DSLR?
My intended target is M45 to start with  |
Hi h0ughy,
Don't forget the old saying about "beauty is in the eye of the beholder".
Clearly you are striving to achieve a result that is somehow more 'realistic'.
But don't forget that color perception in living organisms utilize complex
physiological and psychological mechanisms that provides another layer
of processing and abstraction over the pure physical phenomena that light
is emitted at varying wavelengths.
Therefore one has to be careful when you set the goal of achieving the "true colors"
of a deep sky object, as you would then need to articulate further what that
actually means.
For example, consider the human eye for one moment. Most of us know that
there are three types of cone cells that respond to short, medium and
long wavelengths respectively. We also know that the wavelengths that these
three types of cones respond to overlap to some extent. However, the response
of a cone also varies with the intensity of light and not just the wavelength
and at least two types of cones have to be activated in order for the brain
to perform some differential processing to perceive color and to determine the
intensity of the light.
So it is little wonder that when we view most DSO's visually through amateur
telescopes, they tend to look monochomatic.
Picking M45 as an example, as far as its "true color" is concerned, it is one
thing to observe it with the unaided naked eye from Earth, another to
view it through it from a telescope on Earth and another yet to view it from
a spacecraft 5 feet away. The intensity of light in each case will alter the
perceived color.
In the mid-80's, I had colleagues that were working on early controllers
for color laser printers. "How complex can this color perception thing be", was the
initial attitude. Turns out that color perception is an incredibly complex
area and still not completely understood. Even though we all know about the
cones in the retina, a lot of color processing goes on within the visual cortex
of the brain where various complex tuning goes on. Back in the early 70's,
there was seminal work done by people like Edwin Land (of Polaroid fame)
in this area.
On a final note, I always remember a National Geographic photograph
of color technicians attempting to tune the color of the images transmitted
back from the Viking landers. They were there with a color chip
chart matching it against an 'identical' chip chart being imaged on the side
of the lander. The response of the electronic imaging system was different
to the human eye and it was the best way to calibrate the image.
Now if one could only send a paint chip chart out to M45 you would be set.
Anyway, don't let any of the above put a damper on what you might
be attempting to do. We all know broadly what wavelengths of light
M45 is emitting and reflecting and therefore roughly what its colors might be.
However, this response also acts as a heads-up not to go looking for the
"holy grail" for some "exact, perfect, true color", as in the end color, like
beauty, is in the eye of the beholder.
Best Regards
Gary