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June 15, 2013

Advanced sharpening techniques #1 ; Selective sharpening

All Photoshops' sharpening options have 1 common weakness, they apply 1 sharpening value equally across an entire image.

This can force you to make frustrating tradeoffs to find that 'honey-pot setting'; the sharpening value that allows you to achieve enough crispness for key focal points, without compromising other areas by introducung distracting artefacting or halos.

Through the selective sharpening or compositional sharpening, you can selectively control the degree of sharpness to any area of the image, applying different degrees to different elements.

Taking control

Selective sharpening creates varying levels of sharpness tailored to each scene's elements, allowing you to isolate or excluding parts of the image. With this sharpening workflow you can quite literally 'paint-on' customised amounts of sharpening to each element of your landscape using masks.

This has several benefits;

- Sharpening foreground subjects more than the background, for greater stand out

- Aggressively sharpen key areas, whilst reducing sharpening in artefact or noise prone areas

- Sharpen each element of the landscape as an individual component for truly crisp outputs

Now this tutorial assumes you are output sharpening, so all post work is finished and you have your final flattened digital file ready to open in Photoshop.

Getting started

Much like exposure bracketing, first we need to determine which areas of the image would benefit from greater or lesser levels of sharpening. In this landscape photograph, I defined 3 areas which required different levels to get the optimal result. Using a bracketing number system is also good way to breakdown the image as well.

Defining areas for selective sharpening

+2 High

Here the highest sharpening is earmarked for the rocks and surrounding grasses, as the images foreground focal point and lead in, I want to aggressively sharpen this area to draw the eye's interest and draw it into the frame.

+1 Medium

Dialing down the volume a bit for the midground, I've earmarked this for a general mid-level sharpen to provide some pop to the image, correct for gradual lens softening inherent in a digital exposure.

0 Low

The last element, the background sky, is a naturally 'softer' element than the lower two thirds of the image, so I'm happy to reduce the level of sharpening here to a minimum compared to the rest of the image.

With that decided, we take our flattened file into Photoshop, and follow these steps;

  1. Create 3 layers
  2. Label each layer according to the level of sharpening envisaged -- this isn't manadatory, but I find it useful for ease of navigation later

Your folder stack should now look something like this;

Selective sharpening with masks using layers

Applying your sharpening

There is no difference to your standard workflow at this point.

Other than the fact that you sharpen several times over -- 3 seperate ones (or passes) in this instance. Exaclty how you sharpen is up to you. Photoshop offers many different ways of output sharpening, so choose your specific flavour -- here I went with the High Pass.

Sharpen each layer with the desired level of sharpening, focusing your attention on the element that you earmarked in that layer earlier. This gives you freedom to sharpen each element according to the value you feel is optimal for the item or area. Don't sweat if other areas suffer, provided they are not in the area marked out in that layer we will paint those out later.

Blending the sharpen

With your sharpening setting applied to the whole layer we now need to go back and mask off the areas that we don't want that setting applied to. For this we use masks.

Create a mask on each layer, and start masking out the elements on you don't want to your sharpening level applied too. Your layer stack should start to look something like this;

Selective sharpening with masks using layers

Going into my masks below, you can see I have masked off areas of the image to ensure the level of sharpeningis limited to the elements I choose earlier. So in +2 I masked out everything but the rocks, limiting the most aggressive sharpen to that area alone.

selective sharpening in photoshop with masks

in +1 (mid ground) I masked out the rocks and sky, the rocks already having been sharpened on the layer above (+2), and masked out the sky to retain a level of comparative softness to all other elements.

selective sharpening in photoshop with masks

In 0 (sky) I masked out all two thirds of the image to reveal only the sky.

selective sharpening in photoshop with masks

Work your way down the stack till you are happy that the masks are blended accurately, no areas of the image is missing and the levels of sharpening applied to each area is as desired for our envisaged print.

The final product

Now each element in the image has a tailored sharpening value applied to it, ensuring that it sings in the final print, with no horsetrading around gains in shapreness in one area to loose out to artefacts in another. We flatten the image, save a copy and we are done.

Selective sharpening can be labour intensive. And the more areas you isolate the level of effort goes up, but the level of control gets around any compromises you might have had to make sharpening with 1 pass. Not all images are created equal so why apply equal amounts of sharpening?

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