The Digital Future - A Guide to Digital Camera Reviewing

Image Quality

As we discussed earlier, image quality is largely dependent on the lens. In addition to the lens, the image sensing device that the camera uses also plays a large role. A CCD (charged coupled device) is by far the most commonly used device. A CCD is a small microchip that translates the light that falls on it into an electrical signal. The "megapixel" count that is typically used to rate CCDs is simply a count of the number of pixels that the CCD contains. The more pixels the CCD contains, the smaller the amount of light the camera can pick up and the the higher the image size will be.

Both the camera lens and the CCD determine how true to life the pictures are. In order to measure this typically subjective subject, we have a few tricks up our sleeve.

First is the GretagMacbeth color checker, a small chart that contains patches of scientifically true color. Included for each color is the computer value for the color, making it very easy to reproduce the proper color on the computer. To see how a given digital camera represents color, all we need to do is compare the colors that the camera sees to the colors that are actually there. Below is a chart of the color checker produced in Adobe Photoshop. As you can see, quite a variety of colors are reproduced. To compare the actual colors to the colors that the camera picks up, we simply take a picture of the color checker chart (taken in daylight) and shrink the image down (to get the average value). Then, using the eye dropper tool in Photoshop, we can select the colors that the camera picks up and compare them to the actual colors. Pretty objective, if we do think so ourselves.

In addition, it is necessary to see how any given digital camera performs in a scene of sorts. In order to do this, we have developed our own test scene, shown below, that will be used to not only display different effects a digital camera, but also compare them with other cameras' pictures.

Click here to enlarge.