Pentax K20D Exposure
Three metering systems are available on the Pentax K20D: Multi-segment, Center-Weighted, and Spot. All are accessed through the Metering mode lever below the exposure mode dial on the camera's top panel. In Multi-segment mode, the camera takes an exposure reading from 16 segments and chooses the best exposure based on brightness and contrast across much of the scene. The K20D gives you the option to link AF point to autoexposure in Multi-segment mode, via a Custom menu setting. Center-Weighted metering reads from the center of the frame, but from a fairly large area. Center-Weighted mode is automatically selected if a lens other than a DA, D FA, FA J, FA, F, or A lens is mounted, or when the lens aperture ring is set at other than "A." Spot metering simply reads the exposure from the very center of the image, so you can pinpoint the specific area of the photograph you want properly exposed. (Spot metering is very handy when you have a subject that's backlit, or that has a very different brightness, either lighter or darker, than the background.)
An AE Lock button locks the current exposure settings whenever pressed, so you can independently lock exposure and focus. (AE Lock is useful when you want to base your exposure on an off-center subject. Point the camera at the subject, lock the exposure, then recompose your shot however you like. Your subject will be correctly exposed, regardless of what might be in the center of the frame when you finally snap the shutter.) Through the Setup menu, you can designate the function of the AE Lock button, and how it works in conjunction with the Shutter button.
In situations where exposure compensation is necessary, simply press the Exposure Compensation button and turn the e-dial (in all exposure modes except Manual) and the exposure value (EV) will display in the viewfinder and on the LCDs. EV compensation ranges from -3 to +3 EV when increments of 1/2 EV are selected, or from -2 to +2 EV in increments of 1/3 EV. Or, you can use the Auto Exposure Bracketing function to automatically bracket an exposure in three or five-step increments of either 1/2 or 1/3 EV steps each. AEB is handy for those times when you want to make sure you get just the right exposure for a critical subject.
White balance options include Auto (which ranges from about 4,000K?to 8,000K), Daylight (5,200K), Shade (8,000K), Cloudy (6,000K), Fluorescent Daylight (6,500K), Fluorescent Neutral (5000K), Fluorescent White (4,200K), Tungsten (2,850K), Flash (5,400K), Manual, and Color Temperature, to accommodate a variety of lighting situations. Pressing the Fn button, then the AWB (left arrow) button brings up the White Balance menu. As mentioned, the Pentax K20D offers a Color Temperature setting, which lets you choose from a range of Kelvin temperature settings, from 2,000K to 12,000K. The front e-Dial adjusts the value by 1-step (100K or 20 Mired), while the rear e-Dial adjusts by 10-steps (1,000K or 100 Mired). The Manual option is useful for basing the white balance on a white card. You can also adjust the white balance, controlling the amount of amber, green, blue, and magenta in the color balance, in any of the selected modes. This ability to "tweak" the white balance, called White Balance Fine Tuning, is very helpful when dealing with difficult light sources.
The Pentax K20D also features an "Extended Bracketing" feature, which allows you to take a 3-shot bracket of White Balance, Saturation, Hue, Contrast, and Sharpness. Unlike exposure bracketing, three images are saved with each shot, as all these functions are performed in post-processing, so separate exposures are not required.
The Pentax K20D lets you adjust its light sensitivity, in 1, 1/2 or 1/3 EV steps, with options ranging from 100, to 3,200 ISO equivalents. An Expand Sensitivity Custom menu option allows up to ISO 6,400. An Auto ISO mode in which the camera selects an ISO appropriate to the subject's brightness is also provided. The Auto ISO system seems to adhere to the "1/focal-length for shutter speed" rule, meaning if the focal length is 100mm, the camera will attempt to select a shutter speed of 1/100s and choose a corresponding ISO speed. You can set both the minimum and maximum ISO point for the Auto mode. The higher ISO settings are helpful when you want faster shutter speeds under normal lighting, to help freeze fast action. Of course, as with all digital cameras, the higher ISO settings produce photos with more image noise, in much the same way that higher-ISO films show more film grain. To combat this problem, the K20D offers a High-ISO Noise Reduction option through the Record menu, which reduces the amount of image noise at high ISOs (Pentax doesn't say at what ISO it kicks in). Options consist of Off, Weakest, Weak, and Strong. A second type of Noise Reduction called Slow Shutter Speed NR subtracts a second, dark frame to remove noise and hot-pixels when shooting exposures longer than 0.3 seconds. Settings for that option are Auto and On. The Pentax K20D also offers an Expanded Dynamic Range option, which attempts to preserve highlights and shadows in high-contrast situations. With this mode enabled, the sensitivity range is reduced to ISO 200 to 3,200.
The Pentax K20D offers the user the ability to modify pre-existing image profiles. The K20D offers five image style settings: Bright, Natural, Portrait, Landscape,Vibrant, and Monochrome. The following image parameters can be adjusted for each profile: Saturation (-4 to +4), Hue (-4 to +4), Contrast (-4 to +4), and Sharpness (-4 to +4). Saturation and Hue can only be adjusted when Monochrome is not selected. When using Monochrome, instead of Saturation and Hue, B&W Filter Effects and Toning options are provided. Filter effects consist of Green, Yellow, Orange, Red, Magenta, Blue, Cyan, and Infrared Color. Monochrome can be further modified with a Toning adjustment which allows you to dial in an amount of either selenium style processing (blues) or sepia style processing (browns). The interface allows you to take a sample image with the preview button, or shows you the last image shot, to use as a reference image; adjustments made in the interface are simulated in the sample image.
The Pentax K20D also offers two Self-Timer modes for self-portraits or those occasions when you don't want to risk camera shake on a long exposure by pressing the Shutter button to trip the shutter. You can choose between a two- or 12-second countdown. The two-second countdown is useful for times when you're taking a long exposure with the camera on a tripod, and you want to minimize any camera shake from pressing the Shutter button. In this mode, the mirror is raised immediately after pressing the shutter, giving time vibrations to dampen before the exposure. The Drive Mode setting also accesses Single Shot, Continuous Low, Continuous Hi, Burst, and Remote Control modes, for use with an optional remote. The Remote Control modes offered are immediate release, 3-second delayed release, or continuous.
The K20D also offers an Interval Shooting mode where the interval can be programmed between 1 second and 24 hours, the number of shots between 1 and 99, and the starting time can be immediate or at a set time.
Sequential Shooting Modes
The Pentax K20D offers three Sequential mode that mimic the motor drive on a film camera. According to Pentax, "Continuous Shooting Lo" records JPEGs (using quality level "***") continuously until the card is full at approximately 2.3 frames-per-second. "Continuous Shooting Hi" mode can record up to 38 frames at about 3 frames-per-second. In interesting third mode called "Burst" can capture 1.6-megapixel images continuously at a blazing 21 frames-per-second for up to 115 frames!