Pentax K-S2 Technical Info
Pentax K-S2 Technical Info
by Mike Tomkins | Posted: 02/09/2015
Ricoh has based the Pentax K-S2 digital SLR around a 20.12 megapixel, APS-C sized CMOS image sensor. With dimensions of 23.5 x 15.6mm, it looks to be the same chip used in the entry-level K-S1. It's also the second highest-resolution chip used by Ricoh for its Pentax APS-C DSLR line, bested only by the 24-megapixel sensor of the flagship Pentax K-3.
Just as in that camera (and indeed, most DSLRs these days) there is no optical low-pass filter, which means that per-pixel sharpness should be maximized, but moiré and false color effects could be an issue with certain subjects. However, the presence of Pentax's clever anti-aliasing filter simulation function, first introduced on the K-3 DSLR, means that if you have a problem with moiré or false color you can simply reshoot with the function enabled to avoid the problem.
Total resolution of the K-S2's sensor is 20.42 megapixels, and raw files shot with the camera have a 12-bit depth as in Pentax's other entry-level and mid-range models, rather than the 14-bit depth of flagship models like the K-3.
Another similarity to the K-S1 is the Pentax K-S2's use of a PRIME M II image processor. That's an upgrade from the PRIME M processor featured in the earlier K-30 / K-50 / K-500 DSLRs and K-01 mirrorless camera, but less powerful than the PRIME III processor used in the flagship K-3.
As in all of Ricoh's current Pentax DSLRs at the APS-C sensor size, the Pentax K-S2 offers a sensitivity range of ISO 100 to 51,200 equivalents. The entire range is available by default, with no ISO expansion function needed to access the highest or lowest sensitivity options, and an Auto ISO function is also provided.
Ricoh rates burst performance of the K-S2 in continuous mode at 5.5 frames per second, with a burst depth of 30 large/fine JPEG or nine raw frames.
By way of comparison, the entry-level K-S1 is manufacturer rated just fractionally slower at 5.4 frames per second, with a significantly lesser burst depth of 20 JPEG or five raw frames. The lower-resolution (16-megapixel) Pentax K-50, meanwhile, is manufacturer-rated for a slightly swifter 6.0 frames per second, with similar buffer depths to those of the K-S2. Not surprisingly, all of these cameras are eclipsed by the flagship K-3, with burst shooting at a manufacturer-claimed 8.3 frames per second, and a buffer depth of 60 JPEG or 23 raw frames.
As you'd expect in a Pentax APS-C format DSLR, the Pentax K-S2 accepts K-mount lenses -- whether intended for a full-frame or APS-C image circle -- thanks to the KAF2 bayonet mount on its front deck. Where some affordable DSLRs opt for a less durable plastic lens mount, the K-S2's mount is crafted from stainless steel.
Both screw-drive lenses and those with internal autofocus motors are accepted, and you can also use older Pentax screw-mount lenses or larger-format 645 and 67 lenses with the appropriate adapters. Pentax's power zoom lenses -- of which there are only a few older models, all long-discontinued -- are supported in most respects, but the power zoom-related functionality won't be operational on this body.
Impressively for an affordable camera like this, the Pentax K-S2 is fully weather-sealed, providing a similar level of dust and water-resistance to the flagship K-3 DSLR. There are around one hundred seals throughout the K-S2's body, and a healthy selection of weather-sealed lenses and accessories are also available, making this a great choice if you plan on shooting in rainy or dusty environments.
Launched alongside the Pentax K-S2, the smc Pentax DA-L 18-50mm F4-5.6 DC WR RE lens ships with the camera as a kit, and it's an impressive little optic in its own right.
Priced at around US$300 when purchased separately -- albeit in HD DA rather than smc DA-L form -- the HD Pentax DA 18-50mm F4-5.6 DC WR RE lens is equivalent to a 27.5-76.5mm optic when mounted on one of Ricoh's APS-C Pentax DSLR or mirrorless camera bodies. Its optical formula includes 11 elements in eight groups, and its iris has seven rounded aperture blades.
Just 1.6 inches long when retracted and weighing in at 5.6 ounces, it is nevertheless weather-sealed and can safely be used in rainy or dusty environments. In all, there are ten seals in the design, which also includes a quiet-focusing DC autofocus motor, and Ricoh's HD lens coating which offers a clear advantage over earlier coatings in terms of flare and contrast.
As you'd expect on a Pentax-branded DSLR, image stabilization is handled in the camera body courtesy of a movable platter on which the image sensor is mounted. As well as correcting for horizontal and vertical translational motion, the system used in the Pentax K-S2 can also correct for side-to-side roll. To CIPA testing standards, the system is said to have a three-stop corrective ability.
And if you're an astrophotography fan, you'll be pleased to hear that the system works with the Astrotracer function of Pentax's optional O-GPS1 GPS unit, slowly moving the sensor during exposure to prevent star trails from forming during long exposures.
Of course, even with the best weather sealing in the world, dust is going to get into your camera during lens changes, so some method of removing dust from the sensor is a must. Unlike some affordable DSLRs which use the sensor shift mechanism to shake dust free from the sensor -- not terribly effective, in our experience -- the Pentax K-S2 uses a piezoelectronic element to vibrate the cover glass over the sensor at much higher frequencies. It's the same system used in the flagship K-3, and one which seems to work pretty well in our experience.
Another relatively unusual feature at this pricepoint -- at least, compared to rivals, as past mid-range Pentax models have been similarly generously specified -- is the inclusion of a glass pentaprism viewfinder with a manufacturer-rated 100% coverage. Compared to the pentamirror finders of most DSLRs at this pricepoint, the K-S2's finder should prove noticeably brighter and more accurate.
The Pentax K-S2's viewfinder has 0.95x magnification, just as in the K-S1 and K-3, and an eyepoint of 22.3mm from the center of the viewfinder lens. A built-in dioptric adjustment is available within a -2.5m to +1.5m-1 range, and the standard Natural-Bright-Matte III focusing screen is interchangeable, if you prefer to use a different type.
Note that unlike some competitors, Ricoh hasn't included a proximity sensor adjacent to the viewfinder, so you'll want to disable the LCD monitor manually before raising the camera to your eye.
On the rear panel of the Pentax K-S2 is a 3.0-inch LCD monitor with a total resolution of around 921,000 dots. It uses an air-gapless design with a resin layer that fills the space between the LCD panel and the cover glass, providing better contrast and lower glare. The panel itself is a four dot-per-pixel design which supplements the typical red, green and blue dots with an extra white dot, improving visibility under strong ambient light, and reducing power consumption when shooting indoors or in low light.
In a first for a Pentax APS-C format DSLR, this LCD monitor is mounted on a side-mounted, tilt/swivel articulation mechanism. This allows it to be seen from most angles -- including in front of the camera itself for selfie shooting -- or to be closed facing inwards towards the camera body for an extra modicum of protection from minor knocks, scrapes and smudges.
And interestingly, if you orient the display so as to capture a self-portrait, the K-S2 will automatically switch the function of the Wi-Fi button at the rear right corner of the top deck so that it serves instead as a secondary shutter button. That's a very nice feature, because the Wi-Fi button is much easier to reach than is the standard shutter button, once the camera is turned to point the lens at your face.
Another upgrade relative to the entry-level K-S1, as well as the earlier K-50, is that the Pentax K-S2 sports a refined autofocus sensor.
The number and arrangement of autofocus points -- a total of 11, with the central nine points being cross-types that are sensitive to both horizontal and vertical detail -- is unchanged, but the K-S2's SAFOX X autofocus sensor performs better in low-light shooting. Sensitive to -3EV, it's the same AF module used in 2012's flagship K-5 II and IIs.
In continuous-servo mode, you can choose a single point to focus, and then optionally allow the camera to roam to any of eight surrounding points, handy so that you don't lose focus if you slip off your intended subject briefly.
Exposure and Creative options
The Pentax K-S2 is capable of shutter speeds as fast as 1/6,000 second, and meters exposures using a 77-segment multi-pattern metering sensor. Exposure compensation is available within a +/- 5EV range in either 1/3 or 1/2 EV steps. A built-in, popup flash strobe is included in the design, as is a hot shoe for external strobes, with flash sync at 1/180 second, and flash exposure compensation is within a -2 to +1EV range in 1/3 EV steps.
Exposure modes on offer include Program, Aperture-priority, Shutter-priority and Manual as you'd find on almost any DSLR, although true to Pentax form, they're called P, Av, Tv and M, rather than the more usual P, A, S and M. There are also the usual Pentax-specific modes you'd expect to see present -- Sv (Sensitivity priority) and TAv (Shutter and Aperture priority) -- plus a Bulb position.
Beginners can keep things friendly with both Auto and Scene-mode shooting, the latter providing a selection of 19 scene types. More advanced shooters can recall favorite settings with two User modes, and there's also a new Auto HDR mode on the Mode dial, which captures a three-shot high dynamic range image with clarity adjustment applied. If you want to fine-tune the look of your images for creative effect, a total of 11 custom image modes are provided in the K-S2. There are also nine digital filter functions which provide more eyecatching results.
The clarity adjustment, incidentally, is a new feature and is also available for single-shot, non-HDR images. Rather than the stereotypical (and now rather cliched) crunchy HDR look, with strong sharpening halos around subjects, this aims for a more natural result by tweaking the luminance channel. It provides a similar effect to the Clarity slider in Adobe's Photoshop Lightroom app, but can now be adjusted in-camera.
Want to shoot movies as well as stills? The Pentax K-S2 caters to your needs with the ability to record Full HD (1,920 x 1,080 pixel) video at rates of 30, 25, or 24 frames per second using H.264 compression. If you prefer to trade off some resolution for a higher frame rate, rates of 50 or 60 frames per second are alternately available at HD (1,280 x 720 pixel) resolution.
Movies include stereo audio, either from a built-in stereo mic or a 3.5mm microphone jack in the left side of the camera body, a relatively unusual option in an affordable DSLR. And you can also control the exposure mode for movie capture, with choices of Program, Aperture-priority, Shutter-and-Aperture priority, or Manual exposure -- but not Shutter-priority -- on offer.
And while it can't record 4K ultra-high def movies ordinarily, the Pentax K-S2 is able to create 4K time-lapse movies in-camera. It also offers an unusual "Star Stream" movie mode, which merges multiple frames to create moving star trails in your final video.
Wi-Fi / NFC
Another first for a Pentax DSLR is the presence of in-camera Wi-Fi wireless networking connectivity, complete with Near Field Communications (or NFC) for quick and easy pairing with Android devices. Through a free "Image Sync" app for both Android and iOS smartphones and tablets, the K-S2 can be controlled remotely, complete with a live view feed and the ability to adjust variables such as shutter speed, aperture and ISO sensitivity. It's a much more integrated solution than in past Pentax DSLRs, which at best have offered compatibility with Eye-Fi cards for image transfer, or with Pentax-branded Flucards for image transfer and remote control.
Wired connectivity in the K-S2 includes USB 2.0 High Speed data, a Type-D Micro HDMI high-definition video output, and the aforementioned 3.5mm microphone jack and flash hot shoe.
Images and movies are stored on Secure Digital cards, courtesy of a single SD card slot that is compatible with SDHC, SDXC and UHS-I cards. It also supports Eye-Fi and Flucard types, although given the in-camera Wi-Fi connectivity, there would seem to be little reason to use either.
Power comes courtesy of a proprietary D-LI109 lithium-ion battery pack, the same type used in the earlier Pentax K-S1 and K-50, among others. Battery life is rated at 410 shots on a charge to CIPA testing standards, unchanged from both earlier cameras. Like the K-S1 before it, the Pentax K-S2 is no longer compatible with AA batteries, so you'll want to look to the K-50 instead if you need support for these in the camera body. (And the K-3 can also accept AA batteries courtesy of its optional portrait / battery grip.)
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