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Hello Venkat,I'm sorry for the delay in replying.The z1,z2 values are the intensity stretch parameters. There is no
specific criteria for choosing the values. The same things apply to
simple grey scale display that if one makes the faintest things
visible you may saturate other things. For getting a good color
composite image it is largely a matter of trial-and-error to get the
result you want. If you are asking for a way to get values that best
display the background you could use the display task with
zscale=yes. This uses an algorithm that does fairly well for a broad
range of data. You could take the values printed on the terminal and
move them into rgbsun and that might be helpful.I would also call your attention to the "export" task in the dataio
package. This is a more modern task though with additional
complexity. It implements the zscale algorithm as part of its
intensity stretching calculation.I hope this helps a little.Yours,
Frank Valdes
On Oct 19, 2005, at 5:59 AM, V Venkataraman wrote:> Dear Sir,
>
> I am able to make a composite image using the rgbsun in the color
> package.
> But the resulting image shows some vertical lines near the bright
> stars in
> the field. so i changed the z1,z2 values of the red,green,blue color
> to avoid it. Now the nebulosity which was shown in the K band is
> suppressed while doing this change. What is the criteria for
> choosing the
> z1,z2 values for the individual colors with out loosing the finer
> details
> of nebulosity. Kindly help.
>
> Yours trully,
> Venkat
>
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