Adobe Photoshop CS5 for Photographers - Martin Evening [130]
After you have adjusted all of the above settings, it is likely that the image will have suffered some loss in sharpness. The Sharpen Details slider allows you to dial back in some detail sharpness. I would again urge caution here because adding too much sharpening can simply introduce more artifacts.
Advanced mode noise reduction
In Basic mode you are only able to adjust the Reduce Noise settings so that they affect the overall strength and image detail preservation. When the Advanced mode button is checked you can apply the noise reduction adjustments on a per channel basis (see Figure 4.17). This can be useful if you wish to apply differential amounts of noise reduction to individual channels. For example, whether you are treating a digital capture or scanned film emulsion, the Blue channel is usually the noisiest so it can therefore be a good idea to apply more reduction to this channel and less to the Red and Green channels where the noise is usually less of a problem.
Figure 4.17 This shows a close-up view of the Reduce Noise filter settings in Advanced mode where you can adjust the settings for the individual color channels.
JPEG noise removal
You can also use the Reduce Noise filter to smooth out JPEG artifacts. If you have a heavily compressed JPEG image, the Reduce Noise filter can certainly help improve the image smoothness, but I reckon you can also use the Reduce Noise filter in this mode to improve the appearance of GIF images too. Of course you will need to convert the GIF image from Indexed Color to RGB mode first, but once you have done this you can use the Reduce Noise filter adjustments to help get rid of the banding by taking the Preserve Details slider down to zero % and raise the Sharpen Details slider to a higher amount than you would use normally. Figure 4.19 shows an example of the Reduce Noise filter being used to smooth the banding in a GIF image.
Figure 4.19 The Reduce Noise filter has a ‘Remove JPEG Artifact’ option that can be used to improve the appearance of an image that has suffered from over-heavy JPEG compression. It can also help rescue a GIF image where color levels information has been lost in the conversion to Indexed Color mode. Note that in order to use the Reduce Noise filter a GIF image will have to be converted to RGB mode first. In this example I checked the Remove JPEG Artifact box. To remove the color banding the Preserve Details had to be set to 0% and to make the image sharp again I set the Sharpen Details to 70%.
Saving the Reduce Noise settings
Favorite Reduce Noise settings can be saved by clicking on the Save Changes to Current Settings button which is circled in Figure 4.18. You can also delete saved Reduce Noise settings by clicking on the trash icon next to it.
Figure 4.18 If you click on the Settings menu you can access the Reduce Noise filter preset settings. If you click on the button circled here you can save your own custom preset settings.
Chapter 5. Image Editing Essentials
So far I have shown just how much can be done to improve an image's appearance when editing it in Camera Raw, before you bring it into Photoshop. Some of the techniques described in this chapter may appear to overlap with Camera Raw editing, but image adjustments such as Levels and Curves still play an important role in everyday Photoshop work. This chapter also explains how to work with photos that have never been near Camera Raw, such as images that have been supplied to you directly as TIFFs or JPEGs. I'll start off by outlining a few of the fundamental principles of pixel image editing such as bit depth and the relationship between image resolution and image size. After that we'll look at the main image editing adjustments and how they can be used to fine-tune the tones and colors in a photograph.
Pixels versus vectors
Digital photographic images are constructed of pixels and as such are resolution-dependent. You can therefore only scale the finite pixel image information so far before the underlying pixel