I have said it before, amateurs work more with global adjustments in post processing while professionals use more selective localized adjustments. There are good reasons for so doing, especially when dealing with noise. There are mostly no silver bullets. Everything we do have tradeoffs. Photography by its very nature is all about tradeoffs. Software can totally eliminate noise - I mean 100%. It does not matter how noisy your image is software can fully and totally remove the noise. Yes, even if you shot at ISO 1,000,000 if that is possible? What's the catch? The tradeoff is the catch. The tradeoff of removing noise is the loss of sharpness. Taken to extremes the tradeoff is even mushiness, total loss of detail. So while we can remove all the noise we then also remove all the detail until all we have is a blurred mush. This is why noise is a serious problem and why applying generous global helpings of software noise removal is not the answer. I want my images to be noise free AND sharp. I don't want to choose between having noise OR having the image sharp.

          The best way to avoid noise is to shoot at low (native) ISO and to properly expose - give enough light. However, noise is often unavoidable because of the situations we face. Let me show you:

While this image may look bright enough it certainly did not start off looking this way. There where parts of the lower sky that was rather bright compared to the dark water below (especially in the dark areas). I exposed for the brightest spots in the sky but that left many parts of this image very dark. Those dark sections naturally contain more noise. When you brighter those dark areas the noise also gets amplified, to such an extent that the image can be ruined. This is one reason why I left Canon for Sony. Sony's sensors are just better at dealing with noise when we push our darks brighter. Now Canon people (I was one for years) mock us and the tests we do to show how noise is brought out when we increase the exposure of dark spots by claiming that nobody shoots like that and that we should rather expose better to begin with rather than to underexpose. Well, simply put, you do not always have that option.

          Photography is all about tradeoffs. If I gave this image more light, sure my dark spots would have looked much better but then again the bright spots in the sky would have been blown. You have to pick one or the other (either brights or darks) to correctly expose, it is not possible with one image to expose both the bright areas and the dark areas at the same time (if the dynamic range exceeds certain boundaries). By the way, this image is not a good example of extreme dynamic range as it still has some latitude.

          Either way, I now have an image where the dark areas are too dark. To fix this I just make those sections brighter, but wait, there is a tradeoff as doing so elevates the noise levels. The image is now much better looking, the bright parts are not too bright and the dark parts are now brighter and pleasing BUT I have noise in the darker areas which I don't want. How can we best deal with the noise selectively (locally)? I follow a two step process.

          Firstly, I kill the noise using a duplicate layer. Every image editing software offers this ability. Don't over do it because remember the tradeoff is loss of sharpness and detail. Move the noise removal slider only far enough to just, just get rid of the noise and no further. Adobe Camera Raw also let's you automatically mask only the darker sections so that the loss of sharpness and detail is minimized elsewhere. However, I want more control. I now create a layer mask and simply paint the effect in only where needed (or you can paint it out where not wanted).

          Secondly, I now sharpen the image. Once again, certain software give you the ability to mask in the sharpening so that it only effects areas where you have detail. I still want more control. I create a layer mask again and either paint the effect in or out to where I want or don't want the effect. The trick is to selectively and locally apply the noise reduction only to the areas needing it and sharpening only the areas requiring sharpening. Why? Because sharpening also comes with its tradeoffs. Sharpening makes the noise look worse.

          So let's look at the image of today. The water received noise reduction but no sharpening. The other sections received sharpening but no noise reduction. The secret is to apply what you need to apply ONLY to the areas needing whatever you are doing. Smooth water and soft clouds (with no detail) don't need sharpening so don't apply it there.