Unless one compares side by side an image shot with 8 bit or 16 bit, the difference may not be discernible. Once the image is printed, again one cant see much of a difference as such because of the limitations of the offset or general printing process. There has not bee much development in printing as in the computer monitors. So what is is advantage of shooting at a higher bit depth ? More the Bit depth better it is especially when you need to play around in photoshop or any other retouching / digital software. there are more possibilities and flexibility to change without having a negative impact with higher bit depth images.
There is a much greater flexibility in terms of the final product. Enhanced colours, details, play of shadows and light are some of the few effects that can be achieved with the image. So this is where bit-depth plays an important and crucial role, that is during the processing stage.
A higher bit depth image would have more detail compared to a lower bit depth image. Also the size of the file would be much bigger as it contains more information. The fundamental difference between 16 -bit and 24 -bit is that far more can be done with a 24 bit file as compared to the potential of a 16-bit file. And this very simply translates to the details within an image. There is just more image information available to work with, like more details in highlights, more shadow nuances, more depth in colour. The detail is not unlimited but it certainly has more shadow and highlight detail than the lower bit file.
The technological aspect of bit-depth forms a good basis to grasp the concept. 1 bit is the smallest unit of any digital image; this one bit corresponds to the mechanical on or off, binary 1 or 0, and, when in terms of colour, black or white. That is the extent of its entire capability; it cannot hold more information. 8 bits, when considering the various unique permutations that are possible, can hold up to 256 different pieces of information.
Another point, which usually causes confusion during processing of image files, is the terminology used by a photo editing software for bit-depth. Some software talks about the image as a combination of the channel\'s entire bit rate, whereas some just talk about them as the bit rate for EACH channel. For example, in Photoshop, the file may be displayed as an 8-bit file, even though the original scanned image may be 24-bit. This only means that each channel (R, G & B) has been assigned 8 bits each by the software.
In terms of numbers, 8-bit images can handle 256 levels of information and 16-bit can handle 65,536 (256 x 256) levels of information. That means that there are 65,536 levels of information for each color channel. So, in theory, a 16-bit image has billions of tones of colors that a photographer can use when editing their image.
This kind of information, or depth, is usually required when processing images. Essentially, when processing it is possible to access tonal range beyond what can be seen onscreen.
The benefits for a finished image are the tonal breaks (posterization). This is especially obvious when there is a picture of a graduated blue sky and breaks in the blues are visible. It is also sometimes useful when a portrait of a light-skinned person is taken, where a large part of the face is in shadows. Normally, along the line where the normally exposed skin meets the shadowed areas, there are breaks in the tones. This occurs because there are only 256 levels available and when adjusting in Levels, or Curves (which reflects the 256 levels of information), this information can cause breaks in the tonal range.
Having said this, it is not always necessary to work using a high bit rate, if the exposure is perfect for the situation.
While all this is true, it is not always necessary to shoot at a higher Bit depth. For example, when storage space is a constrain, exposure is fine and images are needed as Jpegs straight out of the camera, 8 bits is just fine. Jpegs are anyways 8 bits. But if you feel you may process or fine tune your images eventually later on, then its better to shoot in RAW at the highest bit depth your camera can shoot. An image shot at a lower bit depth cant be converted to a higher bot depth later on. After processing and manipulation you may save the backup copy at the original bit depth and one for circulation may be reduced to a jpeg for practical reasons.