What is Sharpening for?

• An adjustment to overcome the shortcomings of the ‘process’? Capture process? Print process?
• An adjustment for creative expression?
• Both!

Do we think about sharpening after we’ve applied what looks right on the screen? Do we assess sharpening from the print? Do we experiment beyond what looks right on the screen, to see what it does to the printed result? What could we achieve?

Common beliefs

That USM is the best sharpen tool in the Photoshop box

• Possibly, but there are other ways – filters that are not called ‘Sharpen’ or ‘Unsharp Mask’ – that may be better in the right circumstances.

That you should always sharpen with the image shown on screen at 100% magnification

• There are arguments against this

That you should never sharpen beyond what looks right on the screen

• Often not true

That you should only sharpen as the last action before printing

• Yes, but additionally there is other sharpening that should be applied earlier in the workflow

Quotes from the late Bruce Fraser about output sharpening:

“… it's just about impossible to judge final print sharpness from the display. One of the biggest leaps of faith in the entire Photoshop universe is sending pixels that looks hideous on screen to a printing device, but if the pixels don't look seriously crunchy on the display, you're almost certainly under-sharpening your images. The only reliable way to evaluate print sharpening is to sharpen the image, print it, and look at the print!”

“The first and most important rule in output sharpening is that it must be done at the final output resolution, after any required resampling. There are no exceptions to this rule.”

“The rule of thumb that has served me well is to keep the sharpening haloes no smaller than 1/100th of an inch and no larger than 1/50th of an inch, with the smaller number being preferred for small (up to 11 x 14-inch) prints, dropping to the larger number as dictated by the resolution of the image and the size of the print.”

The parameters of sharpening

‘Sharpen’ and ‘Sharpen More’ allow no control, and are not generally recommended.

(‘Smart Sharpen’ is something that Roger Norton covered in his presentation).

Consider the options in UNSHARP MASK

• Amount – this is some arbitrary measurement in percentage (the actual % is meaningless)
• Radius – the distance in pixels from a particular pixel that will be affected by the calculations
• Threshold – the number of levels between one pixel and the next below which sharpening will not be applied, deployed to ensure that noise will not be sharpened.

It has been found that, in Photoshop, there is some interaction between these settings, which may not suit all situations. However, USM does suit many situations.

Other approaches to experiment with…

1 High Pass

• Copy layer (or merge and copy) – Press Shift+Ctrl+Alt+E (Windows) or Shift+Command+Option+E (Mac OS). Alternatively Hold down Alt (Windows) or Option (Mac OS), and choose Layer > Merge Visible.
• Apply ‘Other’ / ‘High Pass’
• Change blend mode to ‘Hard Light’ / ‘Vivid Light’ / ‘Pin Light’
• Adjust blending options to ensure no sharpening near white and black, and split to achieve gradual transition (mainly underlying layer option)
• Adjust opacity to reduce
• Duplicate to increase

2 Find Edges

• Duplicate layer
• Choose a high contrast Channel and duplicate it (or do Calculations on more than one to create new channel)
• Apply ‘Stylise’ / ‘Find Edges’ to new channel
• Invert new channel – we are creating a mask, and want edge areas to be white not black
• Ensure new channel fills to black and to white
• ‘Select’ / ‘Load Selection’ – creates a selection based on channel levels
• Apply as mask to the new (top) layer
• Delete new channel – no longer needed
• Set blend mode of the new layer to Luminosity
• Now make sharpening adjustments to new image layer to suit image – either normal USM or high pass.
• Can blur the mask to soften the transition between sharpened and not sharpened
• Can adjust the levels of the mask to change effect
• Can change opacity of the layer to change impact.

The gurus of Sharpening

Hard to believe that whole textbooks can be written on the subject. Most well know is that by the late Bruce Fraser (Real World Sharpening with Adobe Photoshop CS2 (Real World) by Bruce Fraser, ISBN-10: 0321449916, ISBN-13: 978-0321449917). Many others have built on his work, and, as a bedrock on the subject, remains largely unchallenged.

Bruce built on earlier work, but, whereas his forebears believed there were two essential phases to sharpening within the workflow, Bruce saw the need for three:

• Capture sharpening. This is intended to overcome the inherent softening of an image at capture time, as a consequence of the physical limit of point sampling via the image sensor, and also the effect of the anti-aliasing filter and the softness of the colour image vs the luminance image. Capture sharpening can be applied to the first non-RAW derivative stage of the image. When using Capture Sharpening, all sharpening in the RAW converter should be turned off (set to zero). A sometimes conflicting requirement in capture sharpening is the need to suppress, ot at least not increase, the noise content.
• Content sharpening. This is sharpening applied to suit the image content, and to a degree, the artistic effect sought. You can imagine that a tree-scape with lots of fine leaf detail might want a different sharpening technique to a portrait of a young lady. Even the portrait might want a stronger level of sharpening around the eyes, but a softer approach to the skin areas.
• Output sharpening. This is the last phase before printing, and the degree of sharpening is adjusted to suit the output. Different printers (eg dye-sub, inkjet) may require different approaches, and different papers play a significant role – matt papers can tolerate much more sharpening than gloss papers, for instance. A key point to remember is that a degree of output sharpening that looks horrendous on screen may be perfect in print.

With three steps to sharpening, and several approaches to each, and several adjustments within each, you can spend a lot of time and money experimenting. Enter Photokit Sharpener, from Pixelgenius, a company headed up by the gurus of the business (including, when he was alive, Bruce Fraser). Name probably most well known to us is Martin Evening (who we tried to get to talk to us on the subject) who is the author of the ‘Photoshop … for Photographers’ series).

Photokit Sharpener takes much of the experimentation out of the workflow, as many sharpening processes have been reduced to sets of pre-defined and tested options, which can still be adjusted.

Note for demonstration prints: all image sharpening strengths left at default values for the demonstration prints – all strengths can be adjusted by changing opacity of the adjustment layer. Some effects will be stronger than desirable, but have been left that way to illustrate effect

Demonstration of PK Sharpener.