Specifications

The Digital Fine Print Course

Editing a Fine Print

16/50

Understanding Unsharp Masking

Sharpening (and blurring) effects are proportional to the degree of enlargement of the final

print. For example sharpening that appears perfectly balanced on a 100 ppi screen will

become excessive when enlarged in a 200 ppi Lambda print. Local effects are proportion-

al to the distance (enlargement) over which they are projected. Therefore it is probably

wise to apply these sharpening and blurring effects only once the final image size has

been established and a test print (not the screen image) has been carefully evaluated.

The AMOUNT is the strength of the filter. In the

Unsharp Mask filter, 500% results in much

darker and lighter outlines (halos) than 100%.

The RADIUS is the width of the outline, in pixels

either side of the boundary being sharpened,

and THRESHOLD is the number of levels of

tonal difference that must first exist across a

boundary for that ‘amount and radius’ to be

applied. Begin adjusting the Adobe Photoshop

Unsharp Mask (USM) filter at a low Radius set-

ting around 0.5 to 2.0 pixels and 0 Threshold

with a high Amount (100% to 500%.). Gradually

increase the Radius until the edges have been adequately ‘outlined’, then slowly increase

the Threshold setting until the effect just begins to wane. Finally reduce the Amount to

suit the image’s character. This will give you the basic sharpening setting for that image.

Always inspect the effects of the Unsharp Mask filter at 100% screen magnification. To

limit unwanted sharpening artifacts such as colour fringing, initially apply the filter to a

duplicate image layer then blend on Luminosity. The duplicate layer will also allow the

sharpening to be locally inserted via a layer mask. The Adobe Photoshop sharpen and

blur filters can also be applied in 16-bit colour depth which will further reduce unwant-

ed image artifacts and promote smoother transitions in the final print.

Unsharp Mask: 500% 1.0 pixels 30 levels