Noise reduction and sharpening - the Smart way
Areas of noise
This was originally written for a friend who had an image that was being rejected for noise and possibly sharpening.
The culprits were possibly the way the image was resized and most likely the sharpening.
Most photographers, when they start out use Photoshop's Unsharp Mask to sharpen their images. This has been around since Photoshop started and it does the job but it comes at a price and that is it applies sharpening globally and un-selectively to your image.
If you understand what depth of field is then there is a portion of your picture that is and a portion that is not in focus, so why would you want to sharpen something that is not in focus?
That's what Global sharpening does, it will try to sharpen, bokeh, clouds and anything else that is not in focus and the way that Unsharp mask, usually abbreviated to USM.
USM works to boost the local contrast between two different colours or boundaries, not enough and the result is soft too much and you generate a white halo around parts of your picture. USM will also look for boundaries in plain areas of colour such as the sky and try to sharpen this, making noise and colour bands in the sky, so only sharpening the things that need to be sharpened and leaving the others alone is a real good way to go about things and to be honest, sorts the plane-spotters with cameras out from the aviation photographers!
My personal favourite is High Pass Filter sharpening, which only sharpens those parts of a picture that has edges, leaving those without with no sharpening at all. There are other methods such as Edge Sharpening and to a lesser extent Photoshops Smart Sharpening Filter.
This tutorial uses Layers. Now layers for the uninitiated seem to be scary but once you get the hang of them will be the best thing since sliced bread. Think on them as sheets of glass that you can paint your picture onto and reveal or conceal without affecting the original at the bottom of the stack of layers.
To access the layer Palate either use the keyboard short cut F7 or WINDOWS, LAYERS from the tool bar along the top of the page.
Create new layer
Duplicate the layer, easiest way is Ctrl + J or LAYER, NEW, LAYER VIA COPY, from the Photoshop Tool bar.
If you don't have any noise issues then you can skip this bit and rejoin at the Smart Object Luminosity blend mode selected stage.
The Nik Software suite is a very useful set of programs and is well worth having. Nik Define is a useful one pass program to reduce noise. My own preference for the more difficult noise removal is Topaz deNoise run manually and not using any of the presets.
Apply the Nik Define to the new layer.FILTER, NIK COLLECTION, NIK DEFINE 2.
(I assue that you know how to do this bit, the Automatic seems to work quite well in most cases. I targeted two areas of noise and removed these manually in Define)
You should end up with a new Layer probably called Define 2.
Define noise reduction layer
Create a new layer mask
On the Define Layer, click on the white rectangle with the dark coloured circle at the bottom of the layers palate. It has been highlighted in red at the bottom of this picture
A white rectangle will appear beside the thumbnail, this is your new Layer mask. I have coloured the background in red to highlight it for you.
The basic way to remember how Layer masks work is White Reveals and black conceals, so we want to conceal the aircraft from the noise reduced Define layer mask preserving the detail in the ground and aircraft and only revealing the noise reduced sky.
You now want to select a brush with a decent size with a hard edge. You now want to select the foreground colour to black.
Look over on the left hand side of the picture I have highlighted this also in red.
This is done by looking at the two squares in the Tools palate. the uppermost one should be black, that's the Foreground colour. The easiest way to do this is to type D to select this and X, which toggles between pure white and pure black, toggle until you see a black square uppermost. Then paint just the aircraft and the grass. You should see a black outline form in the white layer mask rectangle on the right within the layers palate.
Paint the things that you do not want the noise reduction layer to be applied to.
NOTE - I slipped up here as the foreground colour is white, it should be black.
Layer mask, opened on Define layer
Painted Layer mask. White reveals, black conceals
So having painted the layer mask we have allowed the noise reduced layer to be seen and allowing the original picture underneath to remain unaffected.
You can see the effect of the layer mask by clicking the eye icon, highlighted in red in the Define layer mask.
Congratulations, you have survived layer masks!
There are ways of continuing while still retaining the original layers but to keep things simple I will now flatten the layers into a single layer.
When complete, go up to LAYERS and then FLATTEN IMAGE, all the layers will be compressed into a single layer.
At this stage you want to resize down to your final image size, I assume that you are familiar on how this is done.
You can also use the icon to the right of the layers Tab, highlighted in red, click on that and select FLATTEN IMAGE
Smart Object, Luminosity blend mode selected
Sharpening - the smart way to go about things!
Duplicate the layer again Ctrl + J or LAYER, NEW, LAYER VIA COPY.
Just above the new layer, where it ways Normal, click and change this to Luminosity (highlighted in red,) which means that we will only affect the lightness of the picture and not the colour of the picture.(USM sharpening the colour is affected)
Note, this is the Blend Mode, it controls how your new layer is blended onto the layer below.
Right click on the new layer and select CONVERT TO A SMART OBJECT, you will see a small icon appear inside the new layer thumbnail, just as we done with the noise reduction.
Now, FILTER, OTHER, HIGH PASS, go with the default value and OK Do not panic is the picture will go grey and/or multi coloured.
How to select the High pass Filter
Don't panic! It's supposed to look like this
It is worth knowing....
When you apply the High Pass filter, and the screen goes grey, what you are seeing is a mask with only the edges showing. The sharpening is only applied to what you can see in the mask, leaving the sky and everything else intact.The crispness of these lines is a rough guide to the sharpness of the original picture and a out of focus or blurred image will not produce crisp lines.
On the layer Palate, on the new layer that we have made a smart object you should see HIGH PASS and a two arrow symbol, highlighted in red. Double click on double headed arrow symbol and change the mode to OVERLAY (or you can experiment with any of the others within that grouping.) The picture should return to normal now. You will now see the effect of the sharpening.
The Blending Options dialogue box will appear as in the illustration bellow
Selecting the Overlay blend mode
Selecting the Overlay blend mode
This is the really smart bit...double click where it says High pass (Highlighted in yellow) in the layer palate, a small dialogue box should open and you can change the radius to change the sharpening. I cranked the Radius up to 0.5 because I wanted the detail in the aircraft. Don't worry about the halos or jagged edges, well not just yet.
NOTE - the High Pass dialogue box appears in the illustration marked Don't panic above.
Now we get clever again. Click in the white layer mask to the left of where it says Smart Filters. You should see white corner marks appear, (Highlighted in yellow.)
The white layer mask on the Smart Filter Layer
The problem areas and the layer masking
Select a brush, reduce it down to the approximate size of the titles or area that you are concerned about and select Black as the foreground colour, as described above. In this case I will paint over the halo behind the black nose cone and on the tail as well as one or two other parts of the picture. You should see them go fuzzy and back to their unsharpened state.
The areas that I have masked off are outlined in red, including the clouds, which started to pick up some noise.
You should see black marks appear in the white layer mask rectangle, if you don't then check that you have selected the brush tool and that the foreground colour is black at up the top the opacity is 100%
Now press X to select white as the foreground colour and go up the top and select an opacity of say 30%. A quick way is to press the number 3 on your keyboard Then paint over the titles etc. That was a lucky guess. You can paint black and white to apply and erase and vary the opacity to selectively apply the sharpening to your hearts content.
You will notice that I have highlighted the areas in red, also at the reduced capacity. If you have painted a large enough area you may also see grey lines replacing the black ones in the white later mask.
Note: I did not apply any sharpening to the clouds or the black tail in the background. They don't need to be sharpened anyway.
Areas where the sharpening has been reduced or removed
Flatten the image prior to saving
When happy, LAYERS and then FLATTEN IMAGE and save.
This is much better than USM. All this is a bit protracted and seemingly complicated but it sorts the men out from the boys and is made easier when you can write an action to do the steps for you.... but that is for another day.