Pentax K-5 Exposure
Pentax K-5 Exposure
In Multi-segment mode, the camera takes an exposure reading from 77 segments and chooses the best exposure based on brightness and contrast across much of the scene. The K-5 gives you the option to link the AF points to autoexposure in Multi-segment mode, via Custom Function 6, "Link AE to AF Point", but the default is to determine exposure without considering AF point location.
Center-Weighted metering reads from the center of the frame, but from a fairly large area. Center-Weighted mode is automatically selected instead of Multi-segment mode, if a lens other than a DA, DA L, 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 also configure the Shutter button to perform an AE Lock when half-pressed.
In situations where exposure compensation is necessary, simply press the top panel Exposure Compensation button and turn the rear 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 -5 to +5 EV in increments of 1/3 or 1/2 EV, or you can use the Auto Exposure Bracketing function to automatically capture a bracketed exposure with two, three or five frames, varying the exposure between shots by as much as 2.0EV in either 1/2 or 1/3 EV increments. When shooting two shot bracketed bursts, you can opt for the extra frame to be either underexposed or overexposed, compared to the metered shot. You can also control the bracketing order for AEB sequences. AEB is handy for those times when you want to make sure you get just the right exposure for a critical subject.
It's worth noting that the effects of exposure compensation and auto exposure bracketing are additive -- that is to say, if you dial in 5.0EV of exposure compensation, and shoot a five frame bracketed exposure, it's possible for one frame to vary as much as 8.0EV from the metered exposure.
The Pentax K-5 also features an "Extended Bracketing" feature, which allows you to take a 3-shot bracket of White Balance, Saturation, Hue, High/Low Key Adjustment, 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.
For white balance bracketed bursts, the extra frames can vary from the default exposure by one, two, or three steps on blue / amber or green / magenta axes. All other variables can be bracketed anywhere from one to four steps on either side of the default exposure.
Pressing the AWB (left arrow) button brings up the White Balance menu. As mentioned, the Pentax K-5 offers a Color Temperature setting, which lets you choose from a range of Kelvin temperature settings, from 2,500K to 10,000K. 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 setting is useful for basing the white balance on a white card. You can also adjust the white balance in both Color Temperature and Manual modes, controlling the amount of amber, green, blue, and magenta in the color balance using a 2D grid, 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.
When using the K-5's Cross Processing function, white balance cannot be adjusted.
An Auto ISO mode in which the camera selects an ISO appropriate to the subject's brightness is also provided. The default range for Auto ISO is 100 to 3,200, but you can set both the minimum and maximum ISO, as well as select from three parameters which determine how quickly ISO is boosted (slow, normal, and fast). Higher ISO settings are helpful when you want faster shutter speeds under normal lighting, to help freeze fast action.
The Auto and Custom options are both new for the Pentax K-5, and the latter provides an unusually fine-grained degree of control over the camera's high ISO noise reduction behavior. When the Custom mode is enabled, a different setting (Off, Low, Medium, or High) can be configured for every full-stop ISO sensitivity available, including those in the expanded range. If the sensitivity step size is configured to match an exposure compensation step size of either 1/3 or 1/2 EV, the additional sensitivities share a noise reduction setting with the full-stop sensitivity below them, but that's still an unusually fine level of control over high ISO NR -- at most there are three sensitivities required to share any individual NR setting.
A second type of Noise Reduction called Slow Shutter Speed NR subtracts a second, dark frame to remove noise and hot-pixels depending on the conditions, such as shutter speed, sensitivity, and internal temperature. Settings for that option are Auto, On, or Off, where the K-7 simply offered On and Off settings. The On setting applies noise reduction on all exposures longer than one second, while the Auto option applies NR only when the camera deems necessary, taking into consideration the shutter speed, ISO sensitivity, and the camera's internal temperature level.
Expanded Dynamic Range
Another difference has perhaps even greater implications for real-world usage. In the K-7, HDR imaging was only useful when shooting on a tripod, as even slight movement between capture of the source images would otherwise lead to artifacts in the final image. The K-5 can now automatically align the images before combining them, and so is usable handheld, so long as your subject is reasonably static, and your hand somewhat steady.
When enabled, the HDR mode precludes the use of Raw file format, bulb and X-sync exposures, multi exposure, interval shooting, extended bracketing, cross processing, and digital filters. Also, drive modes except single-frame, self-timer, remote control, and remote w/ timer are disabled. Each HDR capture requires a brief processing time to create the final image, and the three source images can't be saved -- they're discarded when processing is complete, which is something we'd love to see changed in future firmware. (On those occasions where the in-camera HDR merge isn't optimal, it might be possible to do a better job manually on a PC, or it might still be desirable to have a copy of the standard exposure image).
An option called Auto EV Adjustment can average the exposure of each individual shot so that the combined image has the same brightness as a normally exposed individual shot. When disabled, the process is additive, just like shooting multi-exposures on film. To understand the difference, imagine a two-frame exposure where the same point is mid-grey in one image, and near-white in the other image. With auto EV adjust disabled, the same point in the final image will be completely white (clipped in every channel). With the adjustment enabled, the same area will have a brightness halfway between that of the same point in the brighter and darker images. An interesting usage of this feature is that multiple frames can be combined in-camera with averaged exposure to yield a single image with reduced noise / an effective exposure longer than would ordinarily be the case without the use of a neutral density filter.
When using Green mode or Cross Processing, the Custom Image mode is fixed to Bright. The adjustment 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. Of course, you can also select between sRGB and Adobe RGBcolor spaces in another menu.
The pre-capture filters are almost identical to those in the previous K-7 model, with two small exceptions. The Extract Color filter can now extract two colors, rather than one, and the Starburst filter adds four new effect shapes. In addition to these pre-capture filters, the K-5 offers ten more in playback mode (Sketch Filter, Water Color, Pastel, Posterization, Miniature, Base Parameter Adjust, Monochrome, Color, Slim, and HDR), and up to 20 filters can be combined in playback mode.
Use of the cross-processing mode isn't possible while shooting Raw images, multi-exposures, extended bracketing, or high dynamic range captures. With cross-processing enabled, access to the custom image and white balance settings are also disabled.
The Pentax K-5 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 Remote Control modes offered are immediate release, 3-second delayed release, or continuous where the first press of the remote starts continuous shooting and a second press stops the burst. The Pentax K-5 has an IR receiver for wireless remotes in the front as well as in the back, which is a really nice feature.
A traditional Auto Exposure Bracketing mode is also provided (in addition to the previously mentioned Extended Bracketing), where 3 or 5 frames can be taken with programmable bracket value and order, and this can be coupled with either an immediate remote control trigger, or a 12-second self timer. Finally, a Mirror Lock-up function is also provided to eliminate camera shake during exposure due to mirror slap. When enabled, the first Shutter button press raises the mirror, and the second takes the exposure. An option is available to enable Mirror Lockup when using a remote control.
As mentioned elsewhere in the review, the Pentax K-5's Shake Reduction system retains the K-7's capability of correctingfor rotational motion. The ability to rotate the Pentax K-5's image sensor opens up a very interesting application, and perhaps one that's more broadly useful than correcting for rotational camera shake.
Given that the camera contains accelerometers (used for determining vertical vs horizontal orientation) that let it precisely determine the camera's position (and hence any tilt relative to an exactly horizontal or vertical position), it makes sense to combine that capability with its rotation-capable SR actuators to come up with a Pentax-exclusive feature: Automatic horizon leveling, or Horizon Correction, as it's called on the Pentax K-5's menu system.
What a brilliant idea! Tilted horizons are a huge problem for amateur photographers, and even not-so-amateur ones who are in a hurry, or who are simply paying more attention to the subject at the moment of exposure than to the orientation of the camera. Trust us, paying attention to both subject and camera orientation simultaneously is harder to learn than you'd think.
The animation at right, taken from our Pentax K-7 review, shows the level of correction available when shooting with shake reduction enabled. The actual angle of the original, tilted shot was 1.3 degrees, and the camera corrected it to a tilt of just 0.3, exactly matching Pentax's spec for the +/- 1 degree correction. With SR turned off, twice as much correction is possible.
Even if you don't choose to use its automatic Horizon Correction function, the Pentax K5 has a useful Electronic Level feature that tells you whether your camera is level or not, in both landscape and portrait orientation. Unlike the single-axis level in the earlier K-7 model, the K-5 now includes a dual-axis electronic level, capable of indicating not only side-to-side roll, but also pitch (front / back tilt) as well. Note, though, that not all of the camera's displays can indicate pitch.
When enabled via a checkbox on Record Menu 4, the bar graph on the top-panel LCD readout that normally shows exposure compensation instead shows a row of dots indicating whether the camera is tilted or not, and in which direction. (Like a bubble level, the dots extend toward the side of the camera that's higher.) The exposure display inside the viewfinder likewise converts to a level display, unless you've just pressed the +/- button on the camera's top panel to adjust exposure compensation. (If you're shooting in Manual or X-sync modes, the exposure guide that's normally shown on the portion of the display occupied by the level gauge is moved to a numeric display that replaces the ISO sensitivity indication.) Interestingly, when the Horizon Correction option is enabled, the top-panel and viewfinder displays don't indicate an out-of-level condition until the camera is tilted more than the +/-1 degree angle that the Horizon Correction feature can fix. Each dot on the top LCD and in the viewfinder display appear to correspond to about 1/3 degree of tilt, and neither of these displays can indicate pitch.
Alternatively, you can enable the Electronic Level display on the rear-panel LCD, by pressing the Info button several times. Once enabled, this shows both roll and pitch with two large bar graph displays -- one horizontal, and one vertical. When there's no roll or tilt, or if the roll is within the range that can be automatically corrected, these displays are shown in green. As soon as the roll or tilt exceeds this threshold, the color of the dots changes to yellow, and once the limit of the display is reached, the dots are shown in red. When the Horizon Correction feature is enabled, two pips appear under the bar graph on the LCD display, indicating the +/-1 degree limit that HC can compensate for. If the camera is level, or within the range that can be automatically corrected, a green line appears under the horizontal graph to indicate that fact. The scale of the tilt indicator on the rear LCD seems to be slightly expanded over that of the top panel readout and viewfinder displays, with each dot appearing to correspond to 1/4 degree of tilt. Adjacent to these is a circular display which shows roll in a more visual manner, and looks somewhat reminiscent of an aircraft attitude indicator. Unlike the attitude indicator, though, this gauge only shows roll, and the line within won't raise or lower to indicate pitch. It does, however, change color to match that of the dots beneath as the level of roll changes.
In Live View mode, two smaller bar graph displays appear in the upper right corner of the LCD screen, displaying a series of dots to indicate roll and pitch angle. The coloring of these displays, white horizon correction pips, and underlining of the horizontal display, also change in the same manner as that shown on the LCD when shooting with the optical viewfinder. Each dot appears to correspond to 1/3 degree of tilt.
The Electronic Level display shown on the rear LCD when shooting through the viewfinder is a bit more sensitive than that shown in the viewfinder and top-panel data readout. It also has a much greater range. When the limit is exceeded, the graphs flash in warning.
When the Horizon Correction option is active, two extra pips appear to mark the limits of its correction ability, and the level-indicating behavior of the graph changes accordingly.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Pentax K-5 Photo Gallery .
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