Binary FX: Photoshop Tech Vault 3.0

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Prepare a Simple USM Layer

How To:

Prepare a sharpen layer using luminosity layer blending with Blend If slider blending options.

Using the simple but powerful optional properties of layers, one can gain enhanced sharpening results over sharpening a single layered image, by using a dedicated Sharpening layer. The superior result is achieved with a luminance blend and by reducing the intensity of the light half of the sharpening halos. The following tip is ideal for sharpening situations where there are high contrast fine edges or where aggressive white haloing is objectionable, but strong dark halos are desired.

Creating the Sharpen Layer:

1a. Single layer, flat background layer images can simply have the flattened background layer duplicated into a true layer, above the original background.

1b. Layered images should have a new blank layer added above the uppermost targeted layer (alt/opt+shift+ctrl/cmd+N). This will become the USM Layer.

Next the alt/opt modifier key is depressed while the Merge Visible layer command is applied (alt/opt+shift+ctrl/cmd+E). The underlying layer data is now merged and added to the blank USM layer.

Adjusting Layer Style Blending Options:

2. Call up the Layer Style Blending Options command (Layer palette menu, Blending Options). Under General Blending, Luminosity is selected from the default Normal layer blend mode. The sharpened colour component of the image is no longer included in the final merged result, avoiding amplification of colour noise.

3. Blend If uses the default composite Blend If: Gray settings, with the key change being the Underlying Layer Blend If slider. Alt/opt click and drag on the right white highlight slider triangle control to split the slider and drag the left half to the extreme left shadow or black point to reduce the intensity of the light half of the USM halo (255 > 0/255).

Note: The preview window in the Unsharp Mask filter dialog box does not preview the merged effect of the luminosity blend and the Blend If slider settings. Simply ignore the preview window when using this technique and make evaluations from the main image window at 100% view with the preview checkbox active, which will give an accurate preview of the merged Blend If process and Luminosity blend.

Once the USM Layer has been created and prepared as in the three steps above, one can then apply the Unsharp Mask filter to the layer.

Further Information:

The intensity of the light half of the sharpening halo is reduced via the Blend If Underlying Layer slider. The results of this method are similar to the more common use of two identical USM filtered layers, with one set to darken blend mode and the other set to lighten blend mode at a reduced opacity, such as 50%. Reducing the light halo intensity can often result in stronger sharpening being applied without objectionable haloing, which is perhaps the most common complaint with images appearing 'too crisp'. There is a subtle difference in how high contrast edges are sharpened, with the Blend If slider method often offering superior results in these areas (with an inferior result in fine highlight detail when compared to the darken/lighten layer method, so image content will often decide the method used). The split Blend If slider can be set at a higher level than zero if one wishes to have a more pronounced light sharpen halo.

Some advocate excluding acquisition sharpening from both the extreme highlights and shadows of the image using the blend if sliders while also using edge masks and luminosity blending (for example, Blend If settings of 15/30 and 225/240 may be used in both upper and lower layer ranges). This is recommended if a further round of final output sharpening is applied. The Blend If technique only uses one layer, so memory overheads are kept to a minimum while offering live preview of the variable sharpen halo intensity prior to filtering. Less commonly, there will be times where one wishes to have a strong light halo and a subdued dark halo, but these image types are not as typical (simply reverse the technique, using the shadow slider instead of the highlight slider).

The benefit of the luminosity blend is that only the important gray levels are sharpened, avoiding amplification of colour noise and colour artifacts found in the colour component of the image which do not add to the appearance of image sharpness. One can also use this technique in a Lab mode document, sharpening only the L channel in a duplicate USM layer taking advantage of the layer Blend If sliders.

Related Links:

How To: Edge Mask

Graphics Articles: SharpControl

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