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There are many problems that can affect the visual quality of a slideshow image. Problems that can show up in images include the following:
The images below illustrate these problems: Why do these problem show up in images? If you are like me, sometimes you just want to point-and-shoot. I don't always fuss with camera settings--or sometimes I just forget a critical camera setting. For instance, overexposure can usually be avoided by setting the camera to underexpose images by -1/3 to -1 stop: if this is done, detail in bright highlights are not likely to be lost. The camera's exposure compensation is adjusted to do this. Do I always do this? Nope! That's one reason I need a program like Photoshop to correct image defects like that shown in Figure 4. Unfortunately, once highlight detail exceeds the dynamic range of the camera, the detail is lost forever. What can be done in this situation? In Figure 4, we can copy appropriate sky background from another image and replace the blown-out sky. Pasting in replacement background is also a good corrective solution for the flash reflection shown in Figure 7. I do alter my images in this way, when necessary--to make them more closely resemble the scene as I actually experienced it. However, on my website, I make it clear that I do so. Exceeding the dynamic range of the camera's sensor can also cause the posterization effects shown in figure 2. In order to cure this, the affected areas can be treated with a dose of saturation and/or hue adjustment. In low light situations, when I do not use a tripod, I do the best I can with an externally mounted flash unit. Even so, as shown in Figure 3, distant image detail is sometimes shrouded in darkness. Fortunately, the shroud can usually be lifted using Photoshop's Shadow/Highlight adjustments. To correct lens distortion problems, as demonstrated by the curved lines in Figure 6 (and the curved lines in Figure 7), Photoshop has a couple of great tools: the Lens Correction filter and the Free Transform command. With these tools, camera lens distortions can be corrected and crooked horizon lines, as shown in Figure 5, can also be corrected. Other Photoshop tools, such as the Clone Stamp and Spot Healing tools can be used to correct problems such as the dust spot shown in Figure 5. As suggested above, some image problems are due to the high contrast of the scenes we want to capture. Where the dynamic range of the scene is likely to cause loss of detail in either the highlights or shadows, a digital darkroom technique called "Luminance Masking" can be used to help preserve this detail. |
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© Copyright 2004-2006 by Royce Tivel. All Rights Reserved. |