Sharpening method in Photoshop

In part six of our beginners’ guide, John Riley examines an alternative sharpening technique using Lab Color – useful when crisp results are required.

02/12/2010 - 14:03

 

The final sharpened image (left) and original shot unsharpened (right).

Not all subjects suit all techniques and sharpening is one area where many variations of approach are possible.

Our last article examined Unsharp Mask in its basic form which is suitable for all general purpose sharpening.

However, particular subjects may demand a different approach. In the days of film, different films could be used, along with an arsenal of different developers. In this Lab Color sharpening technique we are looking at an effect similar to use of an acutance developer, such as FX-39 or Acutol. In other words, sharp, clean edges and crisp grain structure.

Lab Color
After opening the image, Image S Mode S Lab Color will change the basic construction of the image.
Instead of being made up of RGB we now have three channels: Lightness, a and b. In a similar way to the construction of a monitor image, Lightness is a black & white channel and the colour information is carried separately in channels a and b. This means that we can select the Lightness channel and apply quite high levels of sharpening to it, without causing the colour information to smear and create artefacts. We apply sharpening using Unsharp Mask in a similar way to before, but it is only
being applied to the underlying black & white image.

After sharpening, Image S Mode S RGB restores the file to its normal state for web or printing and it can now be saved.

Converting the image to Lab Color.		Selective sharpening of the Lightness Channel.

The result
The end result will vary depending on the subject and the amount of sharpening applied. These images of a Japanese Garden show one possible use, including fine, intricate detail and sharp edges to the architectural details. Portraits can also be suitable, producing an effect similar to the sharp,
grainy portraits from Eastern Europe that were very popular in the 70s.

Hopefully these simple techniques we’ve covered in six short articles will have helped to develop the basic skills necessary to enable us to produce results that express the ideas we had in mind.

Having practised the basics, we can then move on to more advanced techniques as we continue to learn and explore our personal expression and style.

Words and images by John Riley.

Beginners' Guide To Photography Part 5

Beginners' Guide To Photography Part 6

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