Mastering Digital Photography and Imaging, Chapter 1: Essential Digital Imaging Equipment. Pt. 1. By Sybex | WebReference

Mastering Digital Photography and Imaging, Chapter 1: Essential Digital Imaging Equipment. Pt. 1. By Sybex

Mastering Digital Photography and Imaging, Chapter 1: Essential Digital Imaging Equipment. Pt. 1.

This book excerpt is from Mastering Digital Photography and Imaging ISBN 0-7821-4290-7. All rights reserved. Chapter 1: Essential Digital Imaging Equipment, is posted with permission from Sybex.

Essential Digital Imaging Equipment

In Part One, we will consider the equipment that is used for digital photography and other aspects of imaging: cameras, scanners, computers and pertinent software, basic accessories, as well as photo printers. You will not want or need everything that I’ll discuss, and some of it might be well above your current budget. In that case, consider some of the content as reference material for later use or simply to give you an appreciation for the latest equipment and the most sophisticated capabilities that are available.

While Part One is a buyers’ guide of sorts, it is also far more than that. Because I know that many of you already own some of the equipment that I’ll discuss, this part contains recommendations for getting the most from your gear and its many features. All the advice is based on my extensive experience in testing all types of imaging hardware and software in the real world: making and enhancing thousands of images for both family use and professional purposes. Whether you own basic, affordable equipment and software or high-end products, the following chapters should help you to get the best images with the least amount of frustration.

CHAPTER 1: INTRODUCTION TO DIGITAL CAMERAS

Unless you plan to digitize existing photographs with a scanner, as discussed in Chapter 2, you’ll need a digital camera—often called a digicam—if you want to make digital images. In some respects, these cameras are similar to their 35mm counterparts. They include most of the same features, but gain many others that are exclusive to the digital process.

At first glance, a digicam may seem expensive compared with a 35mm film camera. That’s true, but it can offer better value in the long run, at least for photographers who shoot a great deal. Because digicams store images on a memory card, there’s no need to pay for film or processing; think of the card as “reusable film.” Granted, you’ll want prints of some images, but this is cheaper than paying to print every picture on a roll of film. Digicams are also a lot more fun than 35mm cameras. At a party, for example, you can snap a lot of pictures and show them to friends on the camera’s color display immediately. Delete any rejects and take some pics over again if you’re not happy with the poses or expressions. Many cameras will even record short video clips.

In this chapter, I’ll discuss how digital cameras work, the various types of digital cameras, their primary capabilities, and some of the features that are unique to digital cameras. If you already own a digital camera, you may be thinking of upgrading to a newer model, a more advanced model, or a different type of camera. The following sections can help guide your purchasing decision.

How Digital Images Are Captured

When you turn the camera on and press the shutter button, the aperture in the lens opens to allow light to strike the light-sensitive sensor to record a picture. All digital cameras use these electronic sensors to capture photographic images. There are a variety of sensor types, including CCD (charge-coupled device), CMOS (complimentary metal oxide semiconductor, see Figure 1.1), and LBCAST (Lateral Buried Charge Accumulator and Sensing Transistor Array). All these very technical names describe the different methods used by each type of sensor to accomplish the same goal. That goal is to record the scene before the lens using an array of pixels (an acronym for picture elements) on the sensor to store the tonal and color values of the final image.

Figure 1.1: Several types of sensors, of various sizes, are used for image capture in digital cameras.

Recommendation: CMOS versus CCD Sensors

For practical purposes, there is no substantial difference between the imaging capabilities of a technically advanced CCD and CMOS sensor. Each type has some claimed advantages, but both can produce a high level of image quality. While some very cheap, low-resolution models, including “toy” cameras intended for children, may include low grade CMOS chips, this is not relevant for our purposes. The types of cameras that I’ll discuss in this book all incorporate sensors that are technically excellent. Nearly all compact digicams employ a CCD sensor, while some digital SLR (Single Lens Reflex) cameras employ a CMOS sensor. When considering several digital SLR cameras, the type of sensor should not be a high-priority item in your deliberations.

Although digital cameras can record images in full color, the individual pixels on the sensor can’t actually measure color values. They can measure only the intensity of the light striking the pixel, not the color properties of that light. Therefore, filters are placed in front of the pixels so that each can measure only one of the three primary colors (red, green, and blue) of light. (Sony has introduced a sensor that captures four colors, adding “emerald” (resembling cyan) as the fourth color, but this is not yet in widespread use.) The filters are arranged in a specific order, most commonly using the “Bayer” pattern in which there are twice as many green pixels as red and blue.

Another type of imaging sensor, made by Foveon (www.foveon.com), is not yet in general use in digital cameras.

(At the time of this writing, only the Sigma SD series SLR cameras incorporate this sensor.) Called the X3, it records all three primary colors of light (red, green, and blue) at every pixel. (Other sensors record only one color per pixel, as discussed earlier.) Consequently, cameras with the X3 sensor do not need to interpolate color data and do not need the filter discussed earlier. The first X3 sensor contains 3.43 million pixels, but for every pixel location, there is a stack of three “photo detectors” for a total of 10.29 million. This technology is complex, and it does have some advantages, as I discovered while testing the Sigma SD9. Technically a 3.43 megapixel camera, it produced a level of image quality that I would expect from a 5 megapixel camera, suitable for making 11 ? 16.5~IN prints of excellent quality. Foveon has developed X3 chips of even higher resolution, and some of these may be available in digital cameras by the time you read this book.

When the light projected by the lens comes in contact with the imaging sensor during exposure, the light-sensitive pixels accumulate an electrical charge. More light striking a particular pixel translates into a stronger electrical charge. The electrical charge for each pixel is converted into a specific value based on the strength of the charge so that the camera can actually process the data.

Each pixel in a digital image must contain values for all three of the primary colors to accurately describe the final color of the pixel. Because each pixel on the imaging sensor records only the value of one of those colors, the other values must be calculated based on surrounding values. For most captures this is done within the camera. The final image data can then be written to the camera’s memory card as an image file. An exception to this is the RAW capture format, discussed later in this chapter. When we shoot in a camera’s RAW capture mode, the actual pixel values are recorded and stored in a special data file that needs to be processed using special software (in your computer) to convert it to an image format.


Created: March 27, 2003
Revised: March 17, 2004

URL: http://webreference.com/graphics/digital/1