Making a Tricolor Image
To make a color image of an object, you need to combine three images of the object.
One will be assigned to the blue band, one will be assigned to the green
band, and one will be assigned to the red band.
The SDSS uses the green wavelength picture for the blue band, the red wavelength picture for
the green band and the infrared wavelength picture for the red band. These assignments were
chosen because they are the middle three filters.
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| The Green Filter |
The Red Filter |
The Infrared Filter |
Combined to make a tri-color
image |
Exercise 2.
In IRIS, click on View and select tricolor. Type the name of the
infrared file in the red box, the name of the red file in the green
box, and the name of the green file in the blue box. Do not
include the .fts extension. Click OK. Adjust the max and
min brightness values until you see the image clearly. |
You can also adjust the color balance. If you think your image
looks too blue, you can decrease the intensity of the blue image. If
you want more red, you can increase the intensity of the red image.
Exercise 3.
Click on View and then Colors Adjust. Experiment with
changing the relative intensities of the colors by moving the slider
back and forth for each color. Observe the changes. This galaxy you are working with is in our
Famous
Places. Adjust the color balance and max and min brightness
until your image closely matches the image in Famous Places.
Record the values for the colors and max and min brightness you used. |
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