Sharpen & Blur Filters

Sharpen filters

increase the contrast between neighboring pixels, sharpens focus, creates more contrast and increases appearance of image resolution -

• Sharpen and Sharpen More- increase contrast between neighboring pixels in whatever area is selected (or entire image if nothing selected).
• Sharpen more applies a stronger effect that Sharpen
• Sharpen Edges - sharpens only edges of image while preserving overall smoothness of image
• Smart sharpen -   filter has sharpening controls not available with the Unsharp Mask filter.
  • set the sharpening algorithm or control the amount of sharpening that occurs in shadow and highlight areas.
    
  • Zoom the document window to 100% to get an accurate view of the sharpening. Controls in the Sharpen tabs:
  • Amount Sets the amount of sharpening. A higher value increases the contrast between edge pixels, giving the appearance of greater sharpness.
    
  • Radius determines number of pixels surrounding the edge pixels affected by the sharpening. Higher radius value has wider edge effects and gives more obvious sharpening.
    
  • Remove sets sharpening algorithm used to sharpen the image.
    • Gaussian Blur is method used by Unsharp Mask.
    • Lens Blur detects edges & detail in an image, & provides finer sharpening of detail and reduced sharpening halos.
    • Motion Blur attempts to reduce the effects of blur due to camera or subject movement. Set the Angle control if you choose Motion Blur. Angle Sets the direction of motion for the Motion Blur option of the Remove control.
      
    • More Accurate processes the file longer for a more accurate removal of blurring.
      
    • Click Advanced radio button to see Shadow and Highlight tabs, which let you adjust sharpening of dark and light areas. if the dark or light sharpening halos appear too strong
      
    • Fade Amount Adjusts amount of sharpening in the highlights or shadows.
      
    • Tonal Width controls range of tones in the shadows or highlights that are modified. Smaller values restrict adjustments to darker regions for shadow correction and only the lighter regions for highlight correction.
      
    • Radius controls siize of area around each pixel that is used to determine whether a pixel is in the shadows or highlights.
• Unsharp mask combines features of both sharpen & sharpen edges
  • exaggerates the sharpness of an image's edges
  • 150-300% often used with high resolution images 
  • set radius field in pixels, which affects thickness of sharpened edge
  • low values produce crisper edges,
  • best for images for the web (0.5)
  • Unsharp mask: Amount (1-500%) specifies degree to which image sharpened
  • threshold (0-255) controls how Photoshop recognizes edges in a pixel
  • brightness value of 2 neighboring pixels that must occur if Photoshop to sharpen pixels
  • low value sharpens lots of pixels, high value sharpens very few pixels)
  • For 72 dpi for Web, 0.5 Radius usually works best
  • For 120-180 ppi for printing, use 1.0 radius
  • For high resolution images (300 ppi) use radius of 2.0
  • can also apply Unsharp mask to individual color channels or set of 2 channels for different results
  • Choose color channel with most contrast

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Blur Filters:

Blur filters soften image, and are useful for retouching. Blur filters smooth transitions by averaging the pixels next to the hard edges of defined lines and shaded areas in an image.

woman.jpg; skaters.jpg

• Average finds average color of an image or selection, and then fills the image or selection with the color to create a smooth look.
• Blur: Often used to smooth areas where contrast too high & edges too sharp.  Can blur background to make it fade back: 
• Blur More - increases blur 3-4 times 
• Gaussian blur - Maps pixel color values according to Gaussian bell-shaped curve to level you indicate -- good for getting rid of patterns from paper that occur during scan of a photo - can also use with drop shadows
• Lens Blur adds blur to an image to give the effect of a narrower depth of field so that some objects in the image stay in focus (selected areas) and others areas are blurred.
• Motion blur - makes effect of panning camera (moving camera with motion of image 
• Radial Blur - make image spin (best done on part of image)
• Shape Blur uses specified shape kernel to create the blur.
  • Choose a ustom shape presets, and use the radius slider to adjust its size.
  • load different shape libraries by clicking the triangle and choosing from the list.
  • Radius determines the size of the kernel; the larger the kernel, the greater the blur.
• Smart Blur blurs image with precision
  • Radius value determines the size of the area searched for dissimilar pixels
  • Threshold value determines how dissimilar the pixels must be before they are affected
  • set a mode for the entire selection (Normal) or for the edges of color transitions (Edge Only and Overlay).
  • Where significant contrast occurs, Edge Only applies black-and-white edge
  • Overlay Edge applies white.
• Surface Blur blurs an image while preserving edges.
  • useful for creating special effects and for removing noise or graininess.
  • Radius option specifies size of the area sampled for the blur.
  • Threshold option controls how much the tonal values of neighboring pixels must diverge from the center pixel value before being part of the blur.
  • Pixels with tonal value differences less than Threshold value are not included in the blur.

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