Digital Photography For Dummies. Julie Adair KingЧитать онлайн книгу.
Look for these modes: aperture-priority autoexposure, shutter-priority autoexposure, and manual exposure. These modes let you fine-tune exposure and manipulate depth of field (through the aperture setting) and motion blur (through shutter speed).
Continuous-capture mode
Also called burst mode, this shutter-release mode captures a series of photos with one press of the shutter button, which is especially critical for shooting action. Check the frame rate to find out how many pictures you can capture per second; higher is better.
Flash
A built-in flash or a way to attach an external flash is a must, as are options that let you control whether the flash fires, select which flash mode is used (such as red-eye reduction and slow-sync flash), and adjust flash output (often called flash exposure compensation).
Focusing options
For autofocusing, choose a model that lets you select a specific focus point, use continuous autofocusing (tracks a moving subject), and decide when to lock focus. Also note the number of focus points; the more, the better. Because autofocusing isn’t always foolproof, the option to set focus manually is also essential. See Chapter 7 for focusing details.
ISO options
ISO settings control the camera’s light sensitivity. Choose a camera that offers both automatic and manual control over ISO and delivers good image quality at high ISO settings. See “High ISO performance (low-light picture quality),” later in this chapter, for details.
Lens focal length and quality
Focal length determines how much of a scene you can capture in one shot and plays a role in depth of field. The quality of the lens glass makes a huge difference in the sharpness of your images. See the later section “Looking at Lenses” for more help.
Raw capture
For more control in the editing room and the ability to record the most brightness values, choose a model that offers Raw capture as well as the JPEG format.
Viewfinder
Without a viewfinder, you’re forced to compose shots on the camera monitor, which is difficult in bright sunlight.
White Balance adjustments
White balance affects color accuracy. Look for options that enable you to fine-tune White Balance and create custom white-balance settings.
Metering mode choices
A camera’s metering mode determines which part of the frame is analyzed when exposure is set. Choose a model that offers a choice of metering modes: whole frame, spot, and center-weighted, for example. (Chapter 5 explains.)
How important is picture quality?
Of course picture quality is important — no matter what your photographic interests, you want your photos to look as good as possible. But just as with most products you buy, cameras and lenses that produce the top photo quality cost more than equipment that comes in a notch or two down the scale. So the real point to ponder is, how much are you willing to spend to get the ultimate photo quality? If you want to sell or exhibit your photos, you may not be willing to compromise on quality. But if you’re using your camera for some other purpose, you may be able to save some cash and still be perfectly happy with your photos.
The following sections explain features that affect picture quality. Before you dig in, note that you can’t rely on camera specifications for the final word on image quality. Photos from two cameras with the same specs may differ greatly because of a difference in various internal components. For the full story, check out reviews done by pros who have the equipment and expertise to make accurate and objective photo-quality assessments.
Resolution: How many megapixels?
Digital images are made of colored tiles known as pixels. Camera resolution, stated in megapixels (1 million pixels), indicates the maximum number of pixels the camera can use to create a photo. Chapter 2 discusses resolution in detail, but in terms of picture quality, you need to know just two key points:
For onscreen photos, you need very few pixels. Resolution affects the display size of digital photos, but does not affect picture quality unless you greatly magnify your screen display. For most purposes, such as posting on Instagram or Facebook, a 1 MP (megapixel) image is adequate.
For prints, you need lots of pixels. Figure 1-5 offers a look at the difference between a print with plenty of pixels (left) and one lacking in that department (right). With fewer pixels, it’s easier for the eye to detect that it’s looking at a bunch of squares. There simply aren’t enough pixels to finely render the details of the subject, and diagonal and curved lines appear jagged, or stair-stepped, along the edges.A general guideline is to aim for 300 pixels per linear inch (ppi) of the print size. An 8 x 10-inch print, for example, requires 2400 x 3000 pixels, or a resolution of approximately 7 MP. (Total image resolution is calculated by multiplying the number of horizontal pixels by the number of vertical pixels; 2400 x 3000 equals 7.2 million pixels.)
An important caveat: Not all pixels are created equal. The size of the image sensor that contains those picture building blocks must also be considered, as discussed next. The quality of the camera’s lens is critical, too — all the megapixels in the world can’t compensate for a poor lens.
FIGURE 1-5: A photo that has 300 pixels per inch (ppi) compared to one with a meager 50 ppi shows the impact of resolution on print quality.
Image sensor size: Full frame or smaller?
A photograph is formed when light passes through a lens and strikes a light-sensitive recording medium. In a film camera, the film negative performs the light-recording function. In a digital camera, the image sensor handles the task. The sensor is covered with photosites, which are electronic doodads (that's the technical term) that collect the light data needed to create image pixels.
When you look at camera specs, the sensor type and size should be listed. Most cameras now use a type of sensor called CMOS, which stands for complementary metal-oxide semiconductor. I share that nerdy detail just so you won’t spend any more time worrying about what CMOS means. Instead, turn your attention to the sensor size, which is the critical part of the spec.
A smaller sensor generally produces lower image quality than a large sensor. Why? Because when you cram tons of photosites onto a small sensor, you increase the chances of electronic noise that can degrade the picture. So even if two cameras claim the same resolution, the model with the larger sensor is likely to produce higher-quality images than the one with a smaller sensor.
When sensor size is presented as a single number, such as 1″, the
