Chapter IV, Introduction to Digital Imaging: Lesson III Understanding the Components of Image Quality http://www.kodak.com/country/US/en/digital/dlc/book3/chapter4/lesson3/p01.shtml

Lesson III: Understanding the Components of Image Quality

Like any sophisticated technology, digital imaging offers you a myriad of choices from beginning to end. By understanding the components of image quality, you can begin to make better choices about how you capture, create and use your digital pictures.

All digital images are comprised of pixels All digital images are comprised of pixels. Digital pictures may look very similar to traditional photographs, however, they are really electronic files containing thousands and even millions of pixels. This term, pixel, stands for Picture Element. It is the basic building block or the smallest unit of a digital picture. Each pixel has a unique physical address, size specifications and color values. Magnify a digital picture and you can start to see every pixel. The term PPI stands for pixels per inch and is a measure of how much detail you see in your image. Typically the more pixels, the more detail.

The type of digital camera you have determines how many pixels you capture. A typical VGA-resolution (640 x 480 pixels) digital camera is fine if you are using your images for the web. But if you are thinking of printing your pictures, you'll want a megapixel camera, which captures at least one million pixels.

Some professional photographers use high-end digital cameras that capture up to 6 million pixels.

Use the table below as a guide for best results when printing digital images: Capture Resolution Number of Pixels Maximum Print Size 640x480 307,200 Wallet Size 800x600 480,000 2x2 - inch 1156x864 786,432 5x7 - inch 1536x1024 1,572,864 8x10 - inch

Understanding the role that pixels play in image quality Understanding the role that pixels play in image quality. For the best quality, set your camera to the highest resolution possible. You can always resize your image based upon your application or use. However, when inserting your picture into your application, remember that the more pixels in your image, the bigger the file size and the slower the processing of that image. So, it is important to "right size" your images by matching the resolution (PPI) to your application.

For example, images of 72 PPI on APPLE MACINTOSH Computers and 96 PPI on MICROSOFT WINDOWS-based Computers are just fine for viewing on a monitor because that is the maximum resolution of the monitor display. That level of resolution also is perfect for e-mail, websites and electronic presentations because they are all displayed on monitors.

The resolution of monitors is expressed in dot spacing The resolution of monitors is expressed in dot spacing. The finer the dot spacing, the sharper the images appear. But, even if you have a poor quality monitor, you still can get a good quality printed picture if you have the right tools.

The resolution of your image (number of pixels per inch) determines the maximum size print you can create with photorealistic quality. For example, if you want a 5 x 7-inch print, you will need an image with 150-200 PPI. The more pixels, the more detailed and the smoother your prints will appear. For photorealistic print quality, be sure to use a color inkjet printer with 1200 dpi or a continuous-tone thermal printer. The resolution of printers is generally expressed in Dots Per Inch (DPI). The higher the DPI, the greater the concentration of dots printed, the more detail and the smoother both photographs and line art will appear.

When matching your image resolution to match you application resolution, use an image editing software to either sample up or scale down the number of pixels or image size. During scaling down or compression, the computer selects groups of similar pixels and reduces them into a single pixel. This operation also decreases the number of colors in the image as it reduces quality. Increasing the number of pixels to the original image is called sampling up. The more pixels you add, the more artifacts you will see in the image. Lines in the image may also appear jagged. The larger you make the original image, the more pixels you add. Adding too many pixels will cause visible image degradation. For this reason, it is better to sample down rather than sample up.

It is also important to understand that some image compression or scaling down occurs between image capture and processing-the amount of compression depends upon your specific camera. The best digital cameras use a proprietary image compression algorithm that minimizes the amount and type of compression so as to preserve the quality of the image. Many advanced digital cameras offer an uncompressed TIF option for maximum image quality. Keep in mind that the highest resolution and the lowest compression settings yield the highest quality image.

Chapter IV, Introduction to Digital Imaging: Lesson IV Other Digital Capture Factors That Can Affect Image Quality http://www.kodak.com/country/US/en/digital/dlc/book3/chapter4/lesson4/p01.shtml

Lesson IV: Other Digital Capture Factors That Can Affect Image Quality.

If you have a problem with the quality of your images, chances are you need to look no further than your camera's lens. If you don't have an optical-quality glass lens, your pictures could appear distorted and show signs of color shift. So, it won't matter how high a capture resolution you have, the quality of your lens will definitely affect the edge-to-edge sharpness of your pictures. You should also double-check your camera settings.

Like film, the CCDs of digital cameras also have speed ratings Like film, the CCDs of digital cameras also have speed ratings. The faster the speed of the CCD, the more chance for noise (image artifacts) appearing in the captured image. Typical digital camera ISOs range from 100-160. How picture data is captured, or the proprietary compression algorithms used, also vary from company-to-company and from camera model-to-model. Obviously, the more picture data captured, the closer the picture will resemble the original scene.

Consider the type of light in your picture Consider the type of light in your picture. Today's digital cameras incorporate sophisticated technology that automates many of the camera settings that need to be adjusted or compensated for manually on traditional film cameras. For example, shooting under different types of lighting (using traditional cameras) requires the use of special film or lens filters to "neutralize" the color change caused by different types of lights. By using the built-in white balance setting, your digital camera will automatically compensate for specific or even mixed lighting conditions.

Choose from multiple flash settings Choose from multiple flash settings. The built-in flash unit is not just useful for shooting indoors. With multiple flash settings (auto, fill, redeye, fill/redeye, off), your digital camera can automatically compensate for a multitude of lighting conditions. For example, on a bright day, the fill flash helps to eliminate dark shadows. Or given a highly lit background, the fill flash also keeps your subject from looking too dark. Remember that your flash is only effective up to 10 feet away from your subject.

The redeye setting will eliminate a common photo problem caused by the flash's close proximity to the camera lens. When selected, the flash fires twice automatically. Once to constrict the subject's iris and a second time to provide the amount of light needed for proper exposure. If you are shooting under a variety of lighting conditions, the best flash setting to choose is auto.

The technique for taking great pictures hasn't changed The technique for taking great pictures hasn't changed. The best way to create a high quality digital image is to capture the "best picture" at the time of capture.

Whether you use a traditional or digital camera, these Top 10 Techniques for taking better pictures ring true for everyone. 1.Keep your camera handy. 2. You never know when you might come upon a great picture. 3. Hold your camera steady and compose your shot at the time of capture. 4. Get close. Get closer. Then get even closer to fill the frame with your subject. 5. Keep your subjects busy for a more natural look. 6. Use a simple background and place your subjects slightly off-center. 7. Include a foreground in scenic shots for added interest and a sense of scale. 8. Look for good, natural lighting or take full advantage of your camera's settings to compensate for lack of available lighting. 9. Avoid high contrast scenes, details in shadows and highlights may not be able to be rendered. 10. Check your manufacturer's website for firmware updates to improve your camera's performance.