|
Photoshop CS2
Run iterations of Levels and then Curves first to tweak the signal to noise ratio, then run your filters.
In levels you want to adjust the pointer to the left of the histogram to just start protruding into the data inside the histogram- this throws away all useless data to dark to see (noise).
If the dark sky becomes too bright then shift the mid point of the histogram to the right slightly.
Next you have to strech the histogram to give yourself more spectrum to play with - this is where curves come in. Boost the lowest intensity light more than the brightest - but in doing this you boost noise too. To do this shift the 45 degree line upwards from the bottom lower left a small amount by adding 1-2 control points. Think of this curves as being 4-5 zones. You want to brighten data in zones 1 2 and 3, and possibly dim data in zones 4 and 5 - the brightest stars in the picture.
Then you re level to compensate for boosting noise (e.g. light pollution) as well as data in the dimmest portion of your shots.
|