Masking away noise

MT
Posted By
mail.to.me
Jun 18, 2007
Views
657
Replies
4
Status
Closed
Hello,

Editing high ISO digital camera images typically darken areas do contain more noise than midrange en light areas.

I want to have noise reduction only at more dark areas.
(Smooth and gentle into no noise reduction at more light areas).

Can somebody give a step by step work around how to mask dark areas and only give noise reduction to the images in dark areas.

Thinking to a workaround maybe using two layers. Background layer give full noise reduction (e.g. Noise Ninja plugin). Between top layer and background a mask that shows the dark background region to the top.

I am not experienced enough to have it done in the right way. So please, a simple step by step explanation.


L.O.

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J
jaSPAMc
Jun 18, 2007
Léon Obers found these unused words:

Hello,

Editing high ISO digital camera images typically darken areas do contain more noise than midrange en light areas.

I want to have noise reduction only at more dark areas.
(Smooth and gentle into no noise reduction at more light areas).
Can somebody give a step by step work around how to mask dark areas and only give noise reduction to the images in dark areas.

Thinking to a workaround maybe using two layers. Background layer give full noise reduction (e.g. Noise Ninja plugin). Between top layer and background a mask that shows the dark background region to the top.
I am not experienced enough to have it done in the right way. So please, a simple step by step explanation.

Haven’t done this as I generally don’t use high ISO ‘ratings’.

That said, why not select the dark areas, copy and paste to a new layer, then apply NN to that layer with different settings from the more ‘exposed’ layer’s portions?
I
Infinitech
Jun 18, 2007
L
R
ronviers
Jun 18, 2007
Hi L.O.

One way is to add a threshold layer, Layer>New Adjustment Layer>Threshold, to make your value selections. You can double click on the threshold layer icon to make new selections. Then use the add noise filter, Filter>Noise>Add Noise, to increase the noise in the selected regions.

Good luck,
Ron
MT
mail.to.me
Jun 20, 2007
Léon Obers wrote:

Editing high ISO digital camera images typically darken areas do contain more noise than midrange en light areas.

I want to have noise reduction only at more dark areas.
(Smooth and gentle into no noise reduction at more light areas).

Thanks to everybody in giving a suggestion for noise reduction to particular dark areas. Reading and learning, this is what I finaly found out myself for more noise reduction in dark areas, less in midrange and highlight areas.

– image –> select all (Ctrl+A) –> copy the image (Ctrl+C) – go to the channels section –> create new Alpha channel – paste the image to the Alpha channel (Ctrl+V)
– invert Alpha channel (Ctrl+I)
– gaussian blur Alpha channel between about 2 to 5 pixels – curve Alpha channel change whitepoint –> input/output –> 240/255 (or more difference to have maximum noise reduction for more light "blacks" and dark grays in final image)
+ possible change blackpoint to your liking
(for no noise reduction at all in higlight areas in final image,
e.g. input/output –> 40/0)
– load channel as a selection
– delete Alpha channel (not needed anymore selection is made) – go to layers section –> copy background layer
– noise reduction (e.g. Neat Image plugin) to background copy – deselect selection (Ctrl D)
– change opacity background copy to your liking
(for less noise reduction in comparison with background image) – flatten image

I made an action out of it to have more fast and automatic noise reduction to many images. The last "flatten" function you can disable for manual change of opacity for individual image likings before final result.


Vr.groet – regards, Léon Obers

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