How to Evaluate an Image for Post Processing with Photoshop

By January 24, 2015Post Processing
frequency header

Whether you shoot Jpeg or Raw the sequence of what to look for is the same, but the tools are better in Raw processing and the images respond better to adjustment.

When you first open an image for post processing you should go through this list of items to make a decision on how to proceed before you start any changes. Go through to point 13 and list what you want to do before doing any changes. Re-evaluate as you work through the list of changes.

  1. View the image first at a size as large as it will fit on screen to see what type of image it is:
  • Lots of detail = High Frequency
  • Little detail but wide open areas = Low Frequency
  • A mix of both = Mixed Frequency

The frequency of the image is provides a hint as to what sort of sharpening the image is going to need throughout the post processing process. Usually use the following: for H F use a smaller radius, for L F use a slightly higher radius and for M F use a mix of the 18 plus sharpening techniques unless you have something like Nik Sharpener Pro.

  1. First view the image at 200% and look for noise particularly in the open or low frequency areas as well as in the shadow areas and decide if the image needs noise reduction. After this view the image at 100% and decide if it or any area needs input sharpening.
  2. Return to fitting the full image on screen and look for colour casts.
  3. Next look at Shadows and Highlights and bring both into the range you want.
  4. Next look at the black and white points and see that they are satisfactory.
  5. Lens Correction is also an option to look at, at this point.
  6. Next look for Dust Bunnies at 200% using the hand tool to cover the full area of the image. Return to fit to screen.
  7. Next look for distractions that may need to be removed, especially at the sides.
  8. If a portrait check skin, eyes, hair, lips and teeth. Adjust if necessary.
  9. Relook at sharpening and decide if any Creative Sharpening is required.
  10. Next look at contrast and saturation – correct if necessary
  11. Next look at the optimum crop.
  12. Change colour space to suit use. (For viewing on screen or digital projection sRGB and for printing it will depend on the printer – either sRGB or Adobe RGB. For Litho CMYK.)
  13. Resize for intended use.
  14. Output Sharpen
  15. Decide if any special presentation additions should be used: Border/ Frame or if printed a matt surround and a text title.

Complete this sequence and your picture should be ready for the intended use.

High Frequency

High Frequency

In this image there is a great deal of detail in the structure holding up the Yachts and the surrounding buildings. Sharpening must cater for the detail so as not to over sharpen or to create halos that will make it look soft or just plain ugly.
Low Frequency

Low Frequency

This image consists mainly of the open spaces of sky and sea which can show noise if not sharpened correctly. Portraits usually also fall into the category of low frequency images.
Mixed Frequency

Mixed Frequency

While there is a fair amount of sky and sea there is also much detail which puts it in the mixed frequency category. This image has been sharpened by a single method that extenuates the noise in the bottom left shadow areas. This is an image that needs content sensitive sharpening. In other words sharpening tailored for specific areas.

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