Tech Features
Correcting picture problems
Jun 1, 2009, 9:26 GMT
Washington - Digital cameras are supposed to make taking pictures easier, right? Well, they do in many ways, but that doesn't mean your images always turn out as you expected.
Most problems with digital images can be solved with a little know-how, either at picture-taking time or afterwards, in software. Read on for some examples.
Q: How can I remove red-eye?
A: Most image editing programs today include some type of automatic red eye removal feature. Typically this feature attempts to find the eyes of subjects in your picture and will make the necessary adjustments to rid them of the 'red eye' look. Try Google's Picasa (http://picasa.google.com) if your image editor does not have a red eye removal tool.
Correcting dozens or hundreds of images for red eye, however, can prove tedious at best, so if red eye is a consistent problem in your images, you should know how to avoid it at picture-taking time. Red- eye is caused when your flash is located too close to the lens. This is the case with most compact digital cameras and even some DSLRs. The solution is either to purchase a hot shoe-mountable flash, which gets the light up and away from the lens, or to shoot images without flash.
When shooting without flash indoors or in low light, increase the ISO setting of your camera to 400 or higher. Doing so allows more light into your camera, which in turn permits the camera's automatic metreing system to use a higher shutter speed. Higher shutter speeds will help to ensure that you get images that are free from the blur caused by camera shake. Experiment with ISO levels until your indoor images do not suffer from the blur caused by hand-holding your camera.
Q: Will sharpening my digital images fix problems with focus?
A: Using the sharpening filters - or 'unsharp mask,' as they're sometimes called - in popular image editing programs is generally not a panacea for images that start out blurry. Digital sharpening can make properly-focused images appear sharper, but it does this by enhancing the contrast between different-coloured pixels in your images, not by actually improving the focus of an otherwise poorly- focused photograph.
Sharpening will also not solve the problem of images that are blurry because of minute movements of the camera during image capture. Camera shake shows up more clearly when you're shooting in low light with no flash or with an insufficiently fast shutter speed. Unfortunately, there's really not a convincing digital 'cure' for blurry photographs - other than to know how to avoid taking them.
Q: Sometimes in pictures I take outdoors, the background is brighter than my subject. How can I fix this?
A: The automatic exposure features of digital cameras, as with film cameras, will give preference to the brightest objects in the frame when deciding how to adjust the camera's aperture and shutter speeds. If you're shooting a picture of a friend with the ocean in the background, for example, chances are very good that the brightness of the vast expanse of ocean behind your subject is what the camera will adjust exposure for.
There are a couple of solutions to this problem. First, if you're standing fairly close to your subject, use your camera's built-in flash. This will help to even out the stark difference in lighting between your subject and his or her background. If your subject is too far away for flash to be effective, use your camera's built-in spot metering function.
Spot metering forces your camera to adjust exposure for the object on which you focus rather than for the scene in the viewfinder as a whole. This may result in backgrounds that are slightly blown out - or in which some detail is lost - but your subject should at least be exposed properly.
If you're trying to repair an improperly exposed image after having taken it, you should be able to lighten overly dark areas by experimenting with the dodge tool, which is essentially a virtual paintbrush that allows you to selectively lighten a region of a digital photograph by painting over the part that's too dark. General exposure correction tools within photo editing programs today may also work, but these typically lighten or darken an entire region of a photograph, not just one part.
Q: When I take indoor pictures without flash, the colour is usually off. How can I correct this?
A: There are ways to correct this both before and after you take a picture. Before you take a picture, adjust your camera's white balance setting to match, as closely as possible, the type of lighting in which you are shooting. Most digital cameras have a white balance setting, which is used to adjust the camera's limited ability to recognise colours properly under different lighting conditions. Set the white balance setting to 'shade' or 'incandescent,' and the colours you get indoors without flash should be closer to what you expect.
Even with a proper white balance setting indoors, you may still need to adjust colours once you get your image into an image editing program. To do so, look for the white balance adjustment tool. Typically adjusting white balance - and hence getting the colours right - involves using an eye dropper tool to 'pick' the white or grey area of a photograph. Once your image editor can identify the white or grey area, it can automatically calibrate all of the other colours in the image.
--- Have a computer question? Send it to the Computer Helper at jay@thecomputerhelper.org.
