Software: Photoshop Elements, Photoshop
Skills learnt: Using the Unsharp mask filter to increase the contrast of dull images
Time: 20 mins
Most digital photographers have used the Unsharp Mask filter as a way to add some crispness to photographs that are a little soft. In another application this feature can be used to add some local contrast to flat images in much the same way that multi-contrast printing provides a boost to black & white prints.
The trick with this technique is to forget the way that you have been using the feature. Instead of selecting a high amount and low radius setting, you do the opposite. You drag the amount downwards and the radius upwards. This produces a change in local contrast rather than a sharpening of individual pixels. To use the technique as part of your standard enhancement process you would adjust highlight and shadow points to set the contrast of the whole picture first, then employ the Unsharp Mask filter to increase the local contrast and then use the filter a second time, with different settings, to increase the photograph’s sharpness. With the aid of a layer mask these changes can even be applied to specific parts of a photo.
The Adjust Sharpness filter in Photoshop Elements, or Photoshop’s own Smart Sharpen filter, also contain Amount and Radius sliders which can be employed to produce similar contrast-changing effects.
Other Software: Clarity Slide
The Clarity slider in both Lightroom and Adobe Camera Raw provides a similar local contrast adjustment that you can obtain with the techniques described here.
Backwards USM for Better Contrast page 2
1 As sharpening changes are destructive, Elements users should start by opening a low contrast image then duplicating the background layer (Layer > Duplicate Layer). This way the changes can be made to the copy of the image layer rather than the original. Photoshop CS3 users can use the new Smart Filter option in the program.
2 Set the contrast for the whole image, via a Levels Adjustment layer (Layer > New Adjustment Layer > Levels), dragging the black input slider to the right while holding down the Alt/Opt key until you notice the first clipped pixels. Do the same with the highlight input slider, dragging the control leftwards while holding Alt/Opt down.
3 To change the local contrast, choose Unsharp Mask (Elements: Enhance > Unsharp Mask, Photoshop: Filter > Sharpen > Unsharp Mask) and set the Amount to 0. Normally this would be set to a medium to high value. In CS3, convert the image layer to a Smart Object (Filter > Convert for Smart Filters) first before opening the filter.
4 Next we will push the Radius slider towards the right side of the dialogue. Here I used a value of 85 pixels. Now, with the Preview option selected, start moving the Amount slider to the right. The value you set for this slider will depend on the level of contrast you need for the image.
5 With some photos it is an advantage to be able to apply the local contrast changes to a selected area only. Photoshop users can achieve this by applying the change via the mask associated with the Smart Filter entry. Elements users need to add a second Levels adjustment layer with no adjustment settings just below the Sharpening layer. Now highlight the Sharpening layer and choose the Group with Previous option from the Layer menu and then select the mask of the second adjustment layer and fill it with black (Edit > Fill Layer).
6 With the Levels mask now black and the adjustment layer grouped with the Sharpening layer, the effects of the local contrast changes are hidden. With the mask selected, choose a soft-edged brush and select white as the foreground colour, then paint onto the areas to be changed. By adjusting the opacity of the brush you can alter the strength of the change. If need be, apply the Unsharp Mask filter again to add clarity to the picture. This time use the Unsharp Mask filter in the usual way with the Radius slider set low and the Amount set to a higher value.