The Pentax K-70 vs Sony RX100 III: A Deep Dive into DSLR and Compact Excellence

When faced with choosing a camera in today’s market flooded with options, photographers often find themselves at a crossroads - balancing sensor size, portability, and feature sets against budget and shooting preferences. I’ve spent extensive sessions with both the Pentax K-70 and the Sony RX100 III, two cameras launched within a couple of years but aimed at distinct user bases. Yet, both appeal to enthusiasts chasing quality and adaptability. Here, I unpack their strengths, caveats, and ideal use scenarios from the well-tested vantage point of having pushed both cameras through demanding fieldwork and studio tests.

Handling and Ergonomics – When Size Means More Than Weight

At first touch, these cameras could not be more different. The Pentax K-70, a compact SLR body, tips the scales at approximately 688 grams with a solid grip and somewhat imposing dimensions - 126x93x74 mm. It clearly caters to photographers craving the tactile, traditional DSLR experience complete with a pentaprism viewfinder and the reassuring heft that often correlates with durability and stability.

In contrast, the Sony RX100 III is a jewel of compactness: just 290 grams and 102x58x41 mm of primarily magnesium alloy goodness. It fits easily into a jacket pocket or purse, making it an exceptional travel companion. However, compactness comes at the expense of that full DSLR-type grip, sometimes requiring a bit more care in handholding, especially in challenging shooting conditions.

The Pentax benefits from a weather-sealed body - a notable advantage for landscape or outdoor shooters who can’t afford downtime in damp or dusty environments. Sony’s RX100 III, while robust in build quality, lacks such sealing, placing some limitations on its use in more severe weather.

Both cameras feature intuitive control layouts, but the Pentax K-70 shines in physical dials and customizable buttons, making quick manual adjustments convenient during shoots. The RX100 III’s fewer buttons and dependence on menus reflect its compact design philosophy, which might feel restrictive to photographers accustomed to DSLR command immediacy.

Sensor Technology and Image Quality – APS-C Versus 1” Sensor Dynamics

The heart of any camera is its sensor, and here lies one of the most defining differences. The K-70 packs an APS-C CMOS sensor measuring 23.5 x 15.6 mm with 24 megapixels - true high-resolution territory. It does away with the anti-aliasing filter, enabling sharper images, though at a slight risk of moiré in certain scenes. With a native ISO range nominally from 100 to an astounding 102,400, it confidently carries shooters through low-light scenarios, though noise becomes increasingly apparent past ISO 6400 in real-world use.

Sony’s RX100 III sports a smaller 1" BSI-CMOS sensor (13.2 x 8.8mm) with 20 MP. BSI (backside illumination) technology enhances its low-light performance, and while it trails the APS-C in sheer sensor area (116.16 mm² vs 366.60 mm²), it remains formidable for a compact sensor. Its native ISO tops out at 12,800, lower than the Pentax but generally producing excellent noise control for its class.

Real-world testing showed the K-70 delivering richer details, wider dynamic range, and better highlight retention, especially noticeable in landscape and studio shots. The RX100 III’s dynamic range, as evidenced by DXOmark scores (12.3 EV versus typical APS-C ranges closer to 14+ EV in comparable cameras), is more limited, resulting in images that sometimes require cautious exposure to preserve shadow or highlight detail.

Color depth differentiation is noticeable too: the Pentax’s larger sensor affords smoother gradations, particularly crucial in portrait photography where subtle skin tone differentiation matters.

Autofocus and Shooting Performance – Precision Versus Speed

Pentax’s K-70 comes with 11 autofocus points, 9 of which are cross-type - a modest AF array by modern standards. It combines phase-detection and contrast-detection autofocus systems, a hybrid approach that provides decent accuracy in varying lighting conditions. Eye and face detection are present, enhancing portrait shooting precision, but animal-eye AF is notably absent. Continuous shooting peaks at 6 fps, respectable for entry-level DSLRs.

Sony’s RX100 III bundles 25 AF points using contrast-detection only (no phase detection), typical of compacts of that era, but the system is known for smooth and quiet focusing. Its continuous burst hits 10 fps - nearly double the Pentax speed - basic proof that compacts can keep pace in quick action shooting, albeit with buffer limits in RAW capture.

In wildlife or fast sports scenarios, the K-70’s phase-detection ensures more reliable focus tracking despite slower burst rates. For casual sports or street shooting, RX100’s faster frame rate offsets slightly less robust focus tracking. Neither camera supports animal-eye AF, which is an increasingly sought-after feature in modern shooting environments.

Viewfinder and Rear Display – Finding Your Framing Sweet Spot

Pentax’s optical pentaprism viewfinder covers 100% of the frame with 0.63x magnification, providing an immersive shooting experience crucial for daylight compositions where LCD use is impractical.

The RX100 III features a pop-up electronic viewfinder (EVF) with a resolution of 1440k dots and full coverage, a rarity and a boon in large sensor compacts. The electronic VF presents immediate exposure previews, a key professional workflow advantage.

Rear screens on both are 3 inches but differ markedly in flexibility and resolution: the K-70 has a fully articulated LCD with 921k-dot resolution, ideal for low-angle or overhead shots, whereas the RX100 III’s screen tilts upward and downward in a simpler tilting mechanism but offers a slightly higher 1229k dots. Neither support touch input, a slight disappointment given their release timeframe.

Overall, the Pentax excels in usability under varied shooting angles, critical for photographers who work extensively with manual focusing or in macro scenarios.

Lens Ecosystem and Compatibility – Freedom Versus Convenience

A cornerstone of the K-70’s appeal lies in its Pentax KAF2 mount, supporting over 150 lenses including legacy glass - which pentaxians cherish for cost-effective experimentation - and current high-performance primes and zooms. The full DSLR lens ecosystem is huge, ranging from ultra-wide landscapes to telephoto wildlife and macro optics.

The RX100 III has a fixed 24-70mm equivalent f/1.8–2.8 lens, wide enough for landscapes and portraits, yet limited telephoto reach that challenges wildlife and sports applications. On the plus side, the lens is sharp, bright, and closes focus to 5 cm, making it surprisingly adept at casual macro work within its compact form factor.

Thus, the RX100 III offers convenience and versatility for travel and street photographers looking for pocketability with decent zoom, while the K-70 beckons those who want a more specialized and expandable toolkit.

Image Stabilization and Flash Capabilities – Keep It Steady, Light It Right

Both cameras incorporate image stabilization but differ markedly in approach. Pentax’s sensor-shift stabilization works on all lenses, enhancing handholding capability across vintage or modern glass. This is a major plus for low-light shooting and video.

Sony applies optical stabilization within the lens itself, effective but limited to the fixed lens design.

Pentax K 70 front Pentax K 70 screen back Sony RX100 III front Sony RX100 III screen back

Regarding flash systems, the K-70 includes a built-in pop-up flash with standard modes and supports external flashes via its hot shoe - integral for studio photographers and event shooters requiring creative lighting.

The RX100 III’s built-in flash is minimalistic, with no hot shoe for external flash units, reflecting its compact design constraints. It’s fine for fill-flash in daylight but won’t satisfy advanced flash users.

Video Capabilities – The Cinematic Edge

Video-wise, both shoot Full HD 1080p, but Sony holds the edge with additional frame rates (up to 60p interlaced and progressive) and formats (XAVC S), catering more to enthusiasts who desire higher-quality video capture. The RX100 III also offers slow-motion at 120 fps in 720p.

Pentax’s video codec options are more basic: MPEG-4 and H.264, with interlaced 50i/60i capture but no 4K or high-speed formats. That said, Pentax provides a microphone port - a welcome feature for improved audio recording - lacking on the Sony.

Neither has headphone jacks, limiting on-site audio monitoring.

Battery Life and Storage – Longer Haul Versus Compact Convenience

Pentax’s K-70 holds the endurance crown with approximately 410 shots per charge (CIPA standard), reflecting efficient power management and a larger battery size typical of DSLRs.

The RX100 III’s smaller battery delivers about 320 shots per charge - a commendable figure for a compact but potentially limiting for long excursions without spares.

Both support single card slots: Pentax uses SD/SDHC/SDXC (UHS-I compatible), Sony supports SD cards plus Memory Stick Duo variants, offering flexible media choices.

Connectivity and Extras – The Wireless Bridge

Wireless networking is built into both. K-70 includes Wi-Fi for remote control and image transfers, but no Bluetooth or NFC.

Sony RX100 III features NFC and Wi-Fi, facilitating quicker wireless pairing for smartphone remote shooting and sharing through their PlayMemories app ecosystem - a handy perk for social shooters and travel bloggers.

GPS is optional on Pentax; Sony lacks GPS outright.

Performance Scores and Final Verdict

Analyzing overall performance ratings synthesized from lab and field results, the Pentax K-70 solidly scores as a workhorse DSLR with advantages in image quality, versatility, and robust build. The RX100 III ranks highly among compacts, especially for image quality relative to size, autofocusing speed, and video features.

Let’s break that down for distinct photographic disciplines in practice:

• Portraiture: Pentax’s larger sensor and better color depth yield superior skin tones and creamy bokeh, thanks also to its lens options. Sony’s fast lens is credible but limited by sensor size; helpful eye detection improves efficacy.
• Landscape: Pentax dominates with higher resolution and weather sealing; the articulating screen enables tricky compositions. Sony’s compact size helps portability but sacrifices some image quality potential.
• Wildlife: Pentax autofocus and lens choices edge out overall, but Sony’s rapid burst rate grants some advantage in action capture when portability is paramount.
• Sports: Pentax’s 6 fps and phase-detection AF handle sequences well; Sony’s burst speed is faster but less reliably focused at long range.
• Street: Sony excels due to stealth, pocketability, and quick startup, although Pentax is usable if size is not an issue.
• Macro: Pentax’s expandable lens range and IBIS produce sharper close-ups without a tripod; Sony’s close focusing lens is surprisingly capable for casual macro.
• Night/Astro: Larger APS-C sensor in the Pentax wins for noise control at high ISO, though neither is a dedicated astro camera.
• Video: Sony’s feature set is stronger, with superior codec support and frame rates, but Pentax’s mic port is a plus for serious videographers.
• Travel: Sony’s compactness and versatility seem obvious winners, though battery life favors Pentax for extended tours.
• Professional Work: Pentax’s RAW files with robust metadata, DSLR reliability, and external flash support suit professional workflows better; Sony is ideal as a secondary camera.

Who Should Buy Which?

When deciding between these two, it boils down primarily to your shooting style and priorities.

• Buy the Pentax K-70 if:
  You prioritize image quality, lens versatility, and ruggedness for outdoor or studio shooting. It suits enthusiasts willing to carry a mid-sized DSLR for portraits, landscapes, and serious photography where manual control and weather resistance matter. Its higher ISO ceiling and articulate screen appeal across disciplines.

• Choose the Sony RX100 III if:
  Portability, autofocus speed, and advanced video features top your list. This compact packs a punch for travel, street, and casual macro shooting, offering quick operation without the bulk. It’s a brilliant pocket camera when you need high-quality images but don’t want (or need) the complexity of an interchangeable lens.

In essence, the Pentax K-70 embodies the traditional DSLR spirit for well-rounded photographic exploration, while the Sony RX100 III masters the art of compact, high-performance photography with impressive speed and portability. Both cameras carve out strong individual niches, proving that excellence doesn’t always mean one size fits all.

If you’re curious to see how these comparisons pan out in images or want to dive deeper into specific technical benchmarks across genres, I’ve included detailed sample shots and analytic charts throughout this review for your convenience.

Happy shooting!