Digital photos are built of many pixels. Each pixel has a unique value which represents its color. When you are looking at a digital photo your eyes and brain merge these pixels into one continuous digital photo. Each pixel has a color value that is one out of a finite number of possible colors ? this number is known as color depth. Each pixel has a color value that is one out of a palette of unique colors. The number of such unique potential colors is known as color depth. Color depth is also known as bit depth or bits per pixel since a certain number of bits are used to represent a color and there is a direct correlation between the number of such bits and the number of possible unique colors. For example if a pixel color is represented by one bit - one bit per pixel or a bit depth of 1 - the pixel can have only two unique values or two unique colors ? usually these colors will be black or white. Color depth is important in two domains: the graphical input or source and the output device on which this source is displayed. Each digital photo source or other graphics sources are displayed on output devices such as computer screens and printed paper. Each source has a color depth. For example a digital photo can have a color depth of 16 bits. The source color depth depends on how it was created for example the color depth of the camera sensor used to shoot a digital photo. This color depth is independent of the output device used to display the digital photo. Each output device has a maximum color depth that it supports and can also be set to lower color depth (usually to save resources such as memory). If an output device has a higher color depth than the source the output device will not be fully utilized. If an output device has a lower color depth than the source the output device will display a lower quality version of the source. Many times you will hear color depth expressed as a number of bits (bit depth or bits per pixel). Here is a table of common bits per pixel values and the number of colors they represent:
1 bit: only two colors are supported. Usually these are black and white but it can be any pair of colors. It is used for black and white sources and in rare cases of black and white screens.
2 bits: 4 colors are supported. Hardly used.
4 bits: 16 colors are supported. Hardly used.
8 bits: 256 colors are supported. Used for graphics and simple icons. Digital photos displayed using 256 colors are of poor quality.
12 bits: 4096 colors are supported. It is hardly used with computer screen but sometimes this color depth is used by mobile devices such as PDAs and phones. The reason is that 12 bits color depth is the limit for high quality digital photos display. Less than 12 bits screens distort the digital photo colors too much. The lower the color depth the less memory and resources are needed and such devices are resources limited.
16 bits: 65536 colors are supported. Provides high quality digital color photos display. This color depth is used by many computer screens and portable devices. 16 bits color depth is sufficient to display digital photo colors that are very close to real life.
24 bits: 16777216 (approximately 16 million) colors are supported. This is also known as ?true color?. The reason for that nick name is that 24 bits color depth is considered more than the number of unique colors our eyes and brain can see. So using 24 bits color depth provides the ability to display digital photos in true real life colors.
32 bits: in contrast to what some people believe 32 bits color depth does not support 4294967296 (approximately 4 billion) colors. In fact 32 bits color depth supports 16777216 colors which is the same number as 24 bits color depth. The reason for 32 bit color depth existence is mainly for speed performance optimization. Since most computers use buses in multiplications of 32 bits they are more efficient using 32 bits chunks of data. 24 bits out of the 32 are used to describe the pixel color. The extra 8 bits are either left blank or are used for some other purpose such as indicating transparency or some other effect.
Digital cameras are becoming more and more sophisticated. On one hand they allow high quality automatic point and shoot. On the other hand they allow full manual control of their settings. Regardless of the mode you use there are some scenes that require special care. Without such care your digital photos will be of poor quality regardless of how sophisticated and automatic your camera is. New digital cameras include sophisticated hardware and software that allow a simple point a shoot usage and result in high quality digital photos. Such high quality digital photos are achieved in most scenarios but in some scenarios solely relying on the cameras automatic feature is not enough. In such scenes the camera hardware and software will make the wrong decision as to the optimal camera setting for the best digital photo. The result will be a poor quality photo. Being aware of such scenarios can help in avoiding such poor quality digital photos. When you identify such a scenario you can use some simple techniques, by manually setting the camera, by changing the photo shooting angle or by manipulating the scene. One of the common problems with automatic digital camera photo shooting is shaded objects in digital photos. A good example of shaded objects in digital photos is when taking a portrait photo in daylight. The digital camera ambient light sensor measures enough light to set a relatively low exposure value. But even scenes with that have enough ambient light can result in shades that appear on the object depending on the angle of the light source relative to the object. For example if the object is a person with his face lit from the side the object's nose can create shades. Another example is if the object is a person that is wearing a hat and is lit from a light source above ? in such a scene the hat can create shades on the object's face. The camera can not automatically identify such problems and correct them. One way to easily eliminate the shades on the objects is by using the camera fill-in flash. Turn the fill-in flash on. When taking a photo the fill-in flash will fire and will light the shaded areas on the object. One limitation of this solution is that the objects must be within the fill-in flash effective range. Otherwise the flash light will fail to light the object and the shades will not be lit. The best way to learn how to avoid Shaded objects in digital photos is by experimenting and practicing. Try to find scenes that will confuse the digital camera into taking digital photos with Shaded objects. Take a few digital photos using the camera automatic mode and review the results confirming the expected poor quality. Now correct the problem and take a few more photos. Review the new digital photos and make sure that indeed the Shaded objects problem is gone. Practicing in a controlled environment will help you be prepared to quickly and efficiently handle such scenes in real time photo shooting.
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