keeping things sharp

[Daniel-K]

here is a image i have processed recently its 3hrs worth of data but im not happy. how do i keep the sharpness of the image when applying noise reduction? when ever i apply it it seems to kill the sharpness of my image and stars ive tried using masks to no avail any tips greatly welcomed

Dan

[andrewluck]

Masks are the answer, although I find that TGVDenoise preserves detail pretty well without them. How are you generating the mask?

Andrew

[nmoushon]

+1 For masks. But you'll need to explain what you do for your masks.

[Daniel-K]

in PI i just use the range mask and darken the stars and nebula then apply the mask. not sure if this is the right method though

[andrewluck]

Try extracting the luminance from the image, use ATrousWaveletTransform to remove layer 1 (removes noise) and use this as a mask (invert to protect the stars and nebula).

This is assuming you're doing this step after the stretch. If before, then you'll need to stretch the masjk before applying it.

Andrew

[RikM]

The best way to reduce noise is more data!

The way I do it in PS is to use Noel's deep space noise reduction as a new layer on top, reduce the opacity to 40 - 60 % and then add a layer mask and paint it black everywhere the detail has been softened by the NR action.

[ollypenrice]

I do it selectively in Photshop but never use masks. I find it simpler and more accurate to select the regions for noise reduction by using the colour select tool. It's usually just the background sky and sometimes some outer nebulous wisps, so I select these, feather slightly and apply NR. If I want to use Noel (very good he is too) I make a bottom layer, apply his Space Noise Reduction, and then select the darks stuff on the top layer as desribed and erase it.

So never NR strong signal and never sharpen faint signal. It's vital to distinguish them. They have opposite requirements.

Olly

PS Rik is right. More data!