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Mottled background (1 Viewer)

Pete007

Well-known member
I have been working on a photograph recently in Photoshop but noticed I have ended up with a mottled looking background instead of it being an even blue sky.
The background appears to be blue but has purple(ish) mottling.
I'm sure I have seen this before but cannot recall what its called or what causes it.
I would therefore appreciate any comments or advice on what I'm doing wrong and what the remedy is.
I have tried to include a much enlarged image showing the problem which I have lightened to show it to better effect.

Your help appreciated - Pete
 

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As someone still trying to learn, can I ask if Chromatic camera noise is somehow different to other or general noise and is the mottling effect characteristic of 'Chromatic camera noise'. ( I can see Noise in other photos but it doesn't have this blue/purple mottling effect as in this case).
Is this something I have done wrong in my workflow and if so can I either eliminate or minimise it ?
I have downloaded the trial or basic version of Neat Image but am not 100% sure I am using this in the most efficient manner.
Any advice is much appreciated.


Agree with above, definatly chromatic camera nosie.
 
Noise comes in two forms chromatic meaning it affects the colour values and luminance which means it affects the brightness. Broadly speaking smaller sensors and high ISOs lead to more noise, the camera is amplifying the signal from the sensor elements and amplifying the noise as well. It is there in the initial image it is not created in the post processing, although if you boost the levels of shadows it can bring it out.

Noise reduction filtering will help but it is important to just use it on the areas where you can see the noise as it has a general softening effect. Use a masked duplicate layer to apply the noise correction to the areas needed. It is also important not to get hung up on noise you can see if you zoom right in to 100%, particularly if you are going to put the image on the web at a fraction of its original pixel size. Open a second window for your image {Window > Arrange > New Window} and size the window to the target size for the image and zoom it so you can see the whole image. Then do all your edits in the original window at what ever zoom is best but you can see at a glance what the full size image looks like. Often the tweaks you do at 100% have little impact on the totality of the image at the size people are going to look at it.
 
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