Workflow for Photo Correction
Many thanks to Kris for giving me permission to post the following information.
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Photo correction tasks break down into two types - those that are applicable to all images, and those that address specific types of defects found only in some images - and the tools in Paint Shop Pro can be categorized in the same way. Adjustments should generally be made in the order of the main categories listed below. (Note: Listed under each step in the workflow are the PSP tools that are associated with each step. Which tools you choose to use will depend on the individual image and your own personal taste - Nightingail). A. General tasks 1. Color balance Automatic Color Balance Manual Color Correction Fade correction Channel Mixer Color Balance Adjust Red/Green/Blue Hue/Saturation/Luminance 2. Contrast Automatic Contrast Enhancement Histogram Adjustment Brightness/Contrast Highlight/Midtone/Shadow Levels Gamma Correction Curves 3. Saturation Automatic Saturation Enhancement Hue/Saturation/Luminance B. Specific tasks 1. Problems due to image source Video images - Deinterlace filter Scanned images from print - Moiré Pattern Removal JPEG images - JPEG Artifact Removal 2. Noise and film grain Digital Camera Noise Removal Edge Preserving Smoothing filter Texture Preserving Smoothing filter Average filter Soften and Soften More Blur and Blur More Gaussian Blur 3. Color Aberrations Chromatic Aberration Removal Filter 4. Scratches Manual Scratch Remover Automatic Small Scratch Removal 5. Specks and dots Salt and Pepper filter Median filter Despeckle 6. Red-eye Red-eye Removal 7. Adding impact Clarify High Pass Sharpen Sharpen and Sharpen More Edge Enhance and Edge Enhance More Unsharp masking As noted before, the filters should generally be applied in the order of the main categories listed above. There are two exceptions: 1. If the image is exceptionally dark or light everywhere, the color information is not very accurate. In this case it is best to adjust contrast before adjusting color. 2. If you are going to be using very high settings of the Clarify picture, it can reduce the saturation of the image. In this case, it is better to run Clarify after contrast adjustment and then follow up with saturation adjustment. These last two sections are, again, directly quoted from Kris' postings on the topic. "A few other pieces of advice: 1. If you don’t have a monitor whose brightness, contrast and gamma are set properly you can get unsatisfactory results. The program works just fine but the display does not show you the results correctly. 2. Before applying the automatic correction filters be sure to crop your image to remove any black or white surround or any frame. Otherwise the automatic filters can become slightly confused because they treat the border as part of the real image information. 3. When using the Salt And Pepper filter, it is best to select the areas of the image with this type of defect and operate on the selection only rather than operating on the whole image. This avoids damage to small speck-like objects such as buttons or eyes, as well as making the filter faster. The same can be true of the Automatic Small Scratch Removal filter, which can treat scratch-like image features as scratches. 4. In general, though it is possible, you will not get the best results if you run Automatic Color Balance, Automatic Contrast Enhancement and Automatic Saturation Enhancement filters on a selection rather than the whole image. This is because these filters are designed to take all the image information into account before making their decisions. 5. Fade Correction is designed as a quick, one-step filter. You may well get better results by first correcting color and then correcting contrast in two separate steps. 6. The Clarify filter brings out detail in the image without sharpening. Sharpening, which mainly influences edges in the image, can be used as a complement to Clarify since these filters do different things. The Unsharp Mask filter offers the most control over the sharpening process. Rationale: While the order is not mandatory in any sense, in most cases it it is optimal. This is particularly true if you are not a good judge of defects in images. I thought I would post some amplification to explain the steps a bit more. Unlike corrections in other software, the PSP photo enhancement filters are designed to to be used to adjust one thing at a time as far as possible - color, contrast, saturation and so on. However, modifying the red, green and blue (RGB) values making up an image tends to change several things at once. Picking the correct order of steps allows you to successively isolate different aspects of the image to adjust. The order is based on the principles upon which human vision works. The first adjustment is Automatic Color Balance. In order to balance color you must change R, G and B channel values relative to each other. This has an inevitable impact on contrast, since we see contrast as a particular combination of R, G and B. Because saturation measures how different a color is from grey of the same lightness, saturation is altered too, simply because balancing color changes what is considered to be grey. For this reason, color should be adjusted before contrast and saturation. Often, the result of color balancing makes the image look flat because contrast and/or saturation change during color balancing, particularly for large color corrections. This is not a problem because subsequent steps will remedy this. There is an exception to color balancing first. This applies when your image is either extremely light or extremely dark - both situations where there can be no strongly saturated colors. As a result, the color information in the image is unreliable and contrast should be adjusted first to compensate for this. The second adjustment is Automatic Contrast Enhancement. It will affect the contrast in the image, which is that component of an image that corresponds to the equivalent black and white photo. It is the main way we see detail. However, because the maximum possible saturation of a color depends on how light or dark it is, the saturation can also be changed in this step when the lightness is altered. This is the reason for applying contrast enhancement before saturation adjustment. The third adjustment is Clarify. While Automatic Contrast Enhancement adjusts the overall contrast of the image, Clarify is a unique filter that modifies local image contrast. The effect is to make detail stand out in a natural way, without artifacts associated with sharpening edges. Since this filter also modifies the lightness or darkness of the image, it can have an effect on saturation too (typically causing a decrease). Consequently, it should be applied before saturation adjustment. The fourth adjustment is Automatic Saturation Enhancement. This filter accurately matches the human perception of saturation. It leaves the color balance and the contrast completely unaffected. As a result, it should be applied after color and contrast have been successfully adjusted. The fifth adjustment is sharpening the image. Using Unsharp Mask provides the most control but Sharpen or Sharpen More are alternatives. These filters all sharpen the contrast at edges in an image, which are distinct transitions in color or lightness. Because of this, sharpening makes little sense until color (balance, saturation) and lightness (global and local contrast) have been properly adjusted. In Unsharp Mask the Radius setting defines which regions of the image will be considered to be edges. Large values cause more of the image to be "edge". Strength determines the amount of sharpening. Clipping allows "weak" edges to be ignored. The larger the setting the more the effect is restricted to strong edges. This allows you to avoid sharpening image noise or JPEG artifacts. Prior to applying sharpening, it is worth testing Edge Preserving Smooth at a low setting (1 or 2). This can eliminate minor noise or film grain, preventing it becoming more visible later when the image is sharpened. An understanding of all this stuff is not really necessary for doing image correction if you just follow the steps. However, appreciating why you see what you see can make you a more effective and efficient user of the tools. Happy photo enhancement." - Kris Zaklika |
Nightingail's Workshop
