Pentax K-5 vs Sony RX100

Choosing Your Next Camera: Pentax K-5 vs Sony RX100 - A Hands-On Comparison from a Veteran Reviewer

As someone who has logged thousands of hours testing cameras across disciplines - from shooting wildlife in dense forests to capturing fleeting street moments in busy urban jungles - deciding on the right camera is never one-size-fits-all. Recently, I had a chance to revisit two beloved models that represent quite different philosophies: the Pentax K-5, an advanced DSLR with a solid heritage of ruggedness and image quality, and the Sony RX100, a groundbreaking large-sensor compact that redefined pocketability and performance in a small body. This head-to-head offers a blend of detailed technical analysis, real-world testing anecdotes, and candid assessments to help you understand which camera fits your shooting style and priorities.

Let’s dive in.

First Impressions: Size, Handling, and Ergonomics

Right out of the box, the physical presence of these two couldn’t be more different, reflecting their distinct design goals.

The Pentax K-5 commands a substantial yet comfortable presence. With its robust magnesium alloy body, roughly 131mm wide, 97mm high, and 73mm deep, it feels purposeful and reassuring in the hands of someone who enjoys shooting with quad grips and extensive button controls. Weighing 740 grams, it carries a reassuring weight that balances well with Pentax’s extensive lineup of K-mount lenses.

On the flip side, the Sony RX100 is delightfully pocketable - compact and lightweight at just 240 grams and barely twice the thickness of a smartphone (102 x 58 x 36 mm). Ergonomically, it can feel a bit tight for those with larger hands, and there’s a trade-off in fewer physical controls, but for travel photographers and street shooters who prize discretion and portability, this camera excels.

Ergonomics go beyond size though. The top view layouts reveal that the K-5 offers traditional DSLR physical dials for ISO, exposure compensation, and drive modes - fast to access with tactile feedback. The RX100 relies more on menus and multifunction dials, which can slow you down in dynamic shooting scenarios unless you’re intimately familiar with its interface.

For me personally, the K-5’s handling enhances my confidence when framing action or weaving through trail hikes - every control feels within reach. But the RX100 wins points for spontaneous shooting when bulk is a barrier.

Sensor and Image Quality: The Heart of Performance

The proverbial “image quality” debate between larger-sensor DSLRs and compact cameras is nuanced, and I rely on both lab testing and real-world shooting to sort through the claims.

The Pentax K-5 sports a 16MP APS-C CMOS sensor (23.7 x 15.7 mm), delivering a sensor area of 372.09 mm². This significantly larger sensor than the RX100’s 1-inch CMOS (13.2 x 8.8 mm, approx. 116.16 mm²) means it gathers more light, offering better dynamic range, color depth, and high ISO performance - critical in many professional and enthusiast scenarios.

Quantitatively, DxOMark rates the K-5 with an overall score of 82, color depth of 23.7 bits, dynamic range at 14.1 EV, and low-light ISO rating of 1162. In contrast, the RX100 scores 66 overall, 22.6 in color depth, 12.4 EV in dynamic range, and a low-light ISO threshold around 390. While impressive for its class, the RX100’s sensor is inevitably limited compared to the K-5’s APS-C.

What does this mean practically?

In portrait sessions, the K-5’s sensor and lens ecosystem allow for smooth gradations in skin tone, subtle warmth, and superior bokeh with prime lenses. The RX100 can produce sharp images but backgrounds tend to be less creamily blurred, given the smaller sensor and zoom lens aperture ranging F1.8 to F4.9.

For landscape photography, the K-5’s higher dynamic range shines in retaining details in shadows and highlights - especially in sunrise or forest scenes. On the RX100, I found images required more cautious exposure, often leaning on HDR bracketing to compensate.

Night and astrophotography also favor the K-5. The higher ISO usability and longer shutter speeds combined with Pentax’s renowned sensor stabilization offer star trails and sharp nightscapes that the RX100 struggles with unless under optimal conditions.

That said, I must commend Sony’s RX100 for packing a proper 20MP sensor (5472x3648 resolution) into such a small body, enabling surprisingly detailed images under good lighting - even usable RAW files for further editing.

Autofocus Systems: Precision and Speed in Various Scenarios

The autofocus (AF) system is a critical factor where performance nuances really show during fast-moving or critical-focus shoots.

The Pentax K-5 uses an 11-point AF with 9 cross-type sensors - offering phase-detection autofocus capabilities on its DSLR mirror system. It supports AF modes like single, continuous, selective, and face detection during live view. Importantly, its AF tracking is solid for sports and wildlife subjects, coupled with a decent 7 fps burst speed - speedy for its release era.

Conversely, the Sony RX100 relies on a 25-point contrast-detection autofocus array, lacking phase-detection. While its AF speed is quick for a compact and supports face detection and tracking, it won’t match DSLR AF precision and reliability in low contrast or fast-action circumstances. The RX100 pulls off 10 fps continuous shooting, which is impressive for the class, but focus hunting can occasionally interrupt bursts.

In my wildlife tests - tracking small birds flitting among branches - the K-5’s AF system consistently nailed subjects, even in dappled forest light. The RX100 more often missed fleeting wingbeats or lost track during erratic motion.

For street photography, the RX100’s rapid AF and silent operation can be advantageous, allowing quick candid shots without drawing attention. The K-5’s louder mirror slap can be disruptive in quiet settings but excels for deliberate portrait or event work.

Build Quality and Durability: Ready for Adventure or Convenience?

Pentax is famously dedicated to weather sealing and ruggedness - this factor strongly influences a camera’s lifespan in harsh conditions.

The K-5 features a magnesium alloy chassis with comprehensive weather sealing - dustproof and splash resistant. During stormy mountain shoots, I trusted the K-5 to withstand rain and mud, which its predecessors did not consistently manage.

The RX100, despite its refined build and premium feel, is not weather sealed. It’s more delicate in heavy rain or dusty environments - requiring careful protection. It serves better as a grab-and-go camera for controlled or urban conditions where environmental hazards are minimal.

Build quality also includes the reliability of buttons and dials over extended use. The K-5’s mechanical controls feel robust and designed for professional engagement, while the RX100’s compact controls, though well-engineered, suffer more wear with intensive use - as I’ve seen across several compact cameras I’ve tested over the years.

Viewing Experience: Optical vs Digital Displays

The way you compose and review images fundamentally affects shooting flow.

The K-5 uses an optical pentaprism viewfinder covering 100% of the frame with 0.61x magnification. This viewfinder delivers a bright, clear window with natural colors and no lag - ideal for action and precision framing. For me, shooting outdoors in bright light, this optical viewfinder is irreplaceable, maintaining full situational awareness.

By contrast, the RX100 has no viewfinder; composition relies on the 3-inch rear LCD with 1229k-dot resolution and WhiteMagic TFT LCD technology. The screen brightness and resolution are impressive for a compact, but in very bright sunlight, glare can challenge framing. While it supports live view exposure simulation, the lack of eye-level finder means more hand-held shooting at arms-length, which can occasionally introduce camera shake.

Pentax’s fixed 3-inch, 921k-dot LCD in the K-5 is smaller and less bright, but its optical viewfinder compensates for real-time framing, especially with moving subjects.

Lens Options and Flexibility: Expanding Creativity

A camera body is only as good as the lenses you pair with it.

The K-5 benefits from the Pentax KAF2 mount with compatibility for over 150 lens options - from affordable primes to weather-sealed telephotos. This vast ecosystem covers nearly every focal length and specialty lens type (macro, tilt-shift, fisheye), allowing photographers to tailor their kit rigorously.

In contrast, the RX100 has one fixed zoom lens - 28-100mm equivalent at F1.8-4.9 max aperture. It’s surprisingly versatile in range for a pocket camera, but obviously limits opportunities for creative optics, perspective control, or reaching distant subjects. The lens delivers excellent sharpness and contrast for the class but can’t replicate DSLR telephoto or macro performance.

For those who love experimenting with different lenses or working professionally needing specific optics, the K-5’s system gives unmatched flexibility. For casual users or travelers wanting simplicity, the RX100’s lens is a remarkably effective all-in-one.

Battery Life and Storage: Power on the Go

Shooting for extended periods requires reliable battery performance.

The Pentax K-5 uses the D-LI90 battery pack, rated for approximately 980 shots per charge - a robust endurance. In my fieldwork, this meant less frequent battery swaps or the need to carry multiple spares, an important factor in remote or extended photo safaris.

The RX100’s NP-BX1 battery offers around 330 shots per charge, significantly less but understandable given size constraints. For long travel days, I’ve found carrying extra batteries or a portable USB charger essential with the RX100, especially if shooting video or reviewing images frequently.

Storage-wise, both cameras accept SD/SDHC/SDXC cards, with the RX100 uniquely supporting Sony’s proprietary Memory Stick Duo format as well. Both rely on a single memory card slot, requiring careful management of capacity during critical shoots.

Connectivity and Extras: Modern Conveniences

While the K-5 lacks built-in wireless connectivity - only optional GPS modules for location tagging - the RX100 introduced Eye-Fi card compatibility and NFC, features helping streamline quick image transfers and social sharing.

Video capabilities are another consideration.

The K-5 offers Full HD 1080p video at 25 fps using Motion JPEG codec - a bit chunky by today’s standards and lacking advanced codecs, but sufficient for casual video work or integrating clips into storytelling projects. It includes a microphone port but no headphone jack.

The RX100 shoots smoother 1080p at 60 fps and supports AVCHD and MPEG-4 formats. Optical image stabilization aids video smoothness, a clear advantage over the K-5’s sensor-based stabilization which doesn’t assist video recording as effectively. However, the RX100 lacks external mic input, limiting audio enhancements.

Performance Scores and Real-World Use Cases

In aggregate, the K-5 scores higher in tested image quality, low-light sensitivity, and ruggedness, while the RX100 excels in portability, burst shooting speed, and user-friendly video functionality. Detailed genre-based performance evaluation sheds more light:

• Portrait: K-5’s sensor size and lens options provide superior skin tone rendition and bokeh quality. The RX100 is respectable but more limited for shallow depth running.

• Landscape: K-5’s dynamic range and weather sealing triumph; fantastic for outdoor adventure.

• Wildlife: Faster AF and longer reach via K-mount lenses favor the K-5; RX100 best for casual sightings.

• Sports: K-5’s tracking AF and 7 fps put it slightly behind hardcore sports bodies, but superior to RX100’s contrast AF.

• Street: RX100’s discreet profile makes it an excellent street shooter’s companion.

• Macro: K-5 paired with macro primes outperforms RX100’s close focusing limit.

• Night/Astro: K-5’s sensor and long exposure afford greater astrophotography prowess.

• Video: RX100 leads with higher frame rates, better codecs, and superior stabilization.

• Travel: RX100’s compactness is unbeatable; K-5 needs a dedicated bag but offers more versatility.

• Professional: K-5’s RAW support, comprehensive controls, and build quality meet many pro demands.

Sample Imagery: Seeing the Results First Hand

Pentax K 5 front Pentax K 5 screen back Sony RX100 front Sony RX100 screen back

Here, you can observe two landscapes shot side-by-side at base ISO, the K-5 rendering more nuanced tonal gradations and sharpness, while the RX100 captures warmth and color vibrance but with slightly less shadow detail. Portraits from the K-5 illustrate beautiful background separation and eye focus, whereas RX100 portrait shots feel flatter, typical of compact sensors and zoom lenses.

Final Thoughts: Who Should Choose What?

The Pentax K-5 is a powerhouse for enthusiast and semi-professionals seeking a rugged DSLR with high-quality image output, versatility across genres, and compatibility with a rich lens ecosystem. It shines in portrait, wildlife, landscape, and professional photographic work where control, durability, and image quality matter most.

The Sony RX100, by contrast, champions convenience without sacrificing too much on image quality. It’s perfect for travelers, street photographers, vloggers, or enthusiasts who want one pocket-sized tool that handles everyday shooting with speed and decent video - without lugging additional gear.

Summing Up My Recommendations

• Choose the Pentax K-5 if:

  • You prioritize image quality, especially in low light or demanding conditions.
  • You want a durable, weather-sealed build for outdoor adventures.
  • You need a flexible system with extensive lens choices.
  • You often shoot portraits, wildlife, or landscapes where sensor size and control matter.
  • Battery life and ergonomic controls impact your workflow.

• Opt for the Sony RX100 if:

  • You want a discreet, ultra-compact camera for travel and street photography.
  • You value speed and ease of use over ultimate image quality.
  • Video recording with smooth stabilization and higher frame rates is important.
  • You prefer a convenient zoom range in a fixed lens.
  • Portability and quick sharing capabilities trump manual control depth.

Both cameras serve as excellent examples of their categories - DSLR and large sensor compact. They illustrate how technological choices create distinct photographic experiences. In the end, your final call should hinge on your preferred shooting style, use cases, and how much gear you’re willing to carry.

If you’re interested in seeing more sample images or test charts from my evaluation, or have questions about specific shooting situations, don’t hesitate to engage - I’m always eager to help fellow photographers find the right tools for their creative journey.

Happy shooting!