Tuesday, June 26, 2018

SHARPENING METHODS IN PHOTOSHOP


SHARPENING METHODS IN PHOTOSHOP

Software that sharpens an image does so by looking for parts of an image which has significant changes in color or luminosity and it applies contrast to pixels on either side of those changes therefore it gives the appearance of sharpness.

What is the best method for sharpening?  The one that YOU are the most comfortable with.  The purpose of this article is to take a look at the various methods offered by Photoshop.

The methods offered by Photoshop are Sharpen, Sharpen Edges, Sharpen More, Smart Sharpen, Unsharp Mask, and High Pass.  (Fig. 1-1) The first three are blunt in their techniques and should be used with caution.

In this article we are going to look at “Smart Sharpen”, “Unsharp Mask”, and “High Pass”.  There are other methods also and there are presets that can help as well, such as the NIK Collection, Topaz Labs, TKActions by Tony Kuyper and I am sure many more.

UNSHARP MASK:  This filter is flexible in that it gives the user control over its effects. There are three adjustments which can be applied when using this mask, Amount, Radius, and Threshold.  “Amount” controls how much or how little to increase the contrast of pixel edges.  Increase this slider too much and you will get halos around the edges. Increase too little and you will get practically no effect.  For high resolution images experts indicate that you can push this slider to somewhere in the neighborhood of 150% all the way up to 300%. (Fig. 1-2) 

It’s all about your taste.  Remember you can tone it down with the opacity slider. 

“Radius” determines the number of pixels surrounding the edges that will be “contrast-enhanced” to provide the sharpening effect. The greater the value, the wider the edge effects become, and the more pronounced and obvious the sharpening becomes.  It appears that a value, somewhere, between 2 and 3 will yield the best results on an uncropped image from a camera with a sensor of 12Mp or 18Mp.  Your camera’s sensor and your computer monitor can have a bearing on the outcome so experiment with this.  Saved-as Practice image and get away from it for an hour or two or even a day.  Come back and review your practiced image.

“Threshold” determines how different, surrounding pixels are, before considering them for sharpening.  The greater the value, the less the sharpening effect.  I have mine set at 1 but have used a higher value like 2 or 3.  Some experts recommend 3 or 4.

SMART SHARPEN:  This is the Cadillac of the sharpening filters because it gives the user control over sharpening and the sharpening algorithm.  It also allows for controls of sharpening over shadows and/or highlights.  It’s not perfect yet but Adobe is getting there.

The Smart Sharpen dialog window gives two modes of operation. “Basic” and “Advanced”.  (Fig. 1-3) The “Advanced” mode is where you can tweak the shadows and highlights.  There are three tabs in the “Advanced” mode, Sharpen, Shadow and Highlight.  This lets you control how the shadows and highlights areas are dealt with.   The “Amount” and “Radius” sliders work in the same way as they do in the Unsharp Mask.  However there are two additional sliders “Reduce Noise”, and “Remove”.  

Reduce Noise is self-explanatory but remember reducing noise will soften an image.  

The remove option allows you to specify the sharpening algorithm.  For still images the choice is between “Gaussian Blur” and “Lens Blur”.  For moving subjects the option is “Motion Blur”. There are those that believe that “Lens Bur” has the edge in quality when shooting stills.

The “Shadows” slider consists of Fade, Tonal Width, and Radius.  The “Fade” slider controls the amount of sharpening in the shadow areas.  Sliding to the right adds more sharpening while sliding to the left adds less.  The “Tonal” slider controls the range of tones in the shadows that will be sharpened.  They work together with both sliding in the same direction to increase or decrease sharpness.  The “Radius” slider controls the pixels around the shadows but a lot of pros see that it has little effect and recommend just leaving it alone.

The “Highlights” controls are the same as the “Shadows” but targeted to the highlights.  The Smart Sharpen Filter is a RAM hog on a 32 bit system and works best on a 64 bit system.

IMPORTANT:  The most important thing to know is that, since you are sharpening on a pixel basis, different sizes of any given image require different amounts of sharpening – which is fairly obvious, but often overlooked.  So set Photoshop to display an image at “Print Size” when applying sharpening. (Menu>View>Print Size)
  
HIGH PASS: This is not included in Photoshop’s sharpening menu. It is found in a sub-menu in the “Other” section under the “Filter” menu. (Fig. 3-3) In order to use this menu you have to create a duplicate of the background image. (Menu>Layer>Duplicate Layer) and apply the filter to the duplicate layer, with the blending mode set to “Overlay” or “Soft Light”.  However, Soft Light results in less pronounced sharpening. The only control slider is the radius slider.  The larger the number the more the sharpening.  Using this filter is about the same as using the “Unsharp Mask” filter but with less hassle because you have to create a separate layer.  Since sharpening is your last step you could combine all the layers into a combined layer and then apply the sharpening.  Hold down Ctrl, Alt, Shift, and E to create a new layer that combines all the layers underneath it.  Keep in mind this will apply sharpening to all your adjustments as well. 

Rule-of-Thumb, I like to apply sharpening to various parts of my image and not the whole image. To do this I will add a “Black Layer Mask” (Menu>Layer>Layer Mask>Hide All) to my combined layer (Ctrl/Alt/Shift/E) and using a brush set to white will paint sharpening to the areas I want.  I always start with a low capacity (selected from the brush tool bar) and make several passes. I set flow to 100% and smoothing to anywhere from 0 to 100%.  Smoothing prevents the jitters from painting with the brush while using a mouse. I have found that this works great with sharpening wildlife images.
Well that’s it.  I hope this helps and if you have your own method for sharpening please share with the group.

Information for this presentation was obtained from an article by Karl Williams Photography 2011