Sharpening using the High Pass Filter

To sharpen an image in Photoshop Elements I usually turn to “Unsharp Mask” (I had previously used “Adjust Sharpness”). However, I recently discovered an alternative method using the High Pass Filter. Now I have to confess I’m not sure if one is better than the other or whether they are merely three different ways of obtaining the same result. Having said that, from what I can gather the “High Pass” option appears to be primarily used on examples of highly textured images such as, animal fur.

The whole sharpening process works by the software increasing the contrast along the edges of objects within an image. Of course, Elements can’t recognise individual objects so it looks for areas where there is a sudden change in brightness or colour between neighbouring pixels. Our brains interpret this increased contrast as being “sharper”.

There are several methods on the internet of how to use the high pass filter. Some convert the image to a “smart object” first, others head straight for the filter menu. The one described below uses the latter. (As usual, sharpening should occur after you’ve completed all your other processes).

Duplicate the layer “Ctrl+J”. At this stage opinions seem to differ. One method desaturates the image “Shift +Ctrl +U” first. Filter>Other>High Pass. Set the “Radius” to somewhere between 0.5 – 5.0 pixels. Not too much or you will end up with additional noise in the image (if you see any white on the grey screen you’ve gone too far & will get halos). Click “OK”. Change the blend mode to “Overlay” although “Soft Light” (slightly less) & “Hard Light” (slightly harsher) are also viable options. The second method doesn’t bother to desaturate the image & sets the blend mode at the start. This way you can view how the image changes as you increase the radius size.

Once complete, if you feel the effect is too strong, lower the opacity. Alternatively, you can duplicate this layer to increase the effect. If you find the image looks good in some areas but not others use layer masks to apply the sharpening more selectively.

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Colour grading – Natural light effect

This is a 4 step process to achieve a natural light, colour grading effect on your images.

  1. Hue/Saturation adjustment layer. Take the saturation down. Not too much unless you’re looking for a really dramatic effect (which is fine for some studio portraits but not for a “natural” look). About -15 to -20 is a good range.
  2. Curves. We’re going to colour the image using the individual red, green & blue curves. Being subtle is the key here. Maybe bring out the red in the highlights & slight ‘S’ curves in the green & blue but it can vary according to ones individual opinion.
  3. Levels. On the blue channel draw in the triangular markers slightly to bring back some blue in the shadows & reduce it in the highlights to bring back some warmth.
  4. Colour fill layer. Add a new solid colour fill layer & choose a gold colour (eg. d0a702). Change the blend mode to “hard light” & bring the opacity down to about 8%.

As ever, the final step is to sharpen the image using whatever sharpening method you prefer (unsharp mask, adjust sharpness, high pass filter etc.) The above image displays the before & after photographs.

Sharpening

Most digital images require a degree of sharpening in order to look their best. Here are a few tips on how to go about it (& things to avoid too).

Shooting in raw gives you the maximum amount of control over sharpening (so do it!) However, you don’t want to apply the same levels of sharpening to every image, take their content into consideration. For example, if the image has strong edges & bold contrast, adding too much sharpening may lead to halos appearing around objects which will make them look unnatural. Also bear in mind, you’re obviously looking for a balance but in general, under-sharpening is more acceptable than over-sharpening as the latter can create images which look too doctored.

Editing software, such as Photoshop Elements, provides you with three controls for sharpening:

  1. Radius. The radius is used to set the size of the edges you want to enhance. It should be varied according to the detail in your subject. As a rough guide 0.6 is a good starting point & it should rarely go as high as 3.
  2. Amount. This is the strength of the sharpening treatment (100% is a good point to begin).
  3. Threshold. Threshold controls the minimum brightness difference that an edge has to have for the sharpening to be applied. For instance, high values will only apply sharpening to strong (high contrast) edges. If your image has lots of fine detail, a low value is required.

When you’re applying the sharpening it’s often a good idea to view the image at 100%. This way you can focus on the important details. Having said that, don’t forget to view the whole picture at some stage & check for strong edges becoming too bold or developing halos.

Don’t confuse noise with detail. Noise can be a problem in areas of uniform tone (eg. skies) so be careful not to make it more noticeable than it already may be.

How to sharpen selectively. An easy way to sharpen selectively (& thus, ensure those parts of your image which require sharpening get your attention) is to use a layer specifically for this purpose. At the end of your post processing flatten the image & then duplicate it. Now add a fairly strong sharpening treatment to it. Create a layer mask & invert it (Ctrl + I) to hide the effect of the sharpening (the mask icon should turn from white to black after being inverted). Next use a white brush to apply the sharpening where you want it. You can vary the opacity to control the visibility of the sharpening effect.