Pentax K-5 II vs. Sony RX1: An Expert’s In-Depth Camera Comparison for Serious Photographers

Choosing between the Pentax K-5 II and the Sony RX1 is like deciding between two distinct philosophies in photography gear. On one side, you have the Pentax K-5 II - a robust APS-C DSLR designed for the enthusiast who appreciates traditional handling and weather-sealed durability. On the other, the Sony RX1 emerges as a compact full-frame powerhouse, perfectly suited for those who prioritize image quality and portability without sacrificing sensor performance.

Having spent over 15 years in the trenches testing, comparing, and pushing cameras to their limits across genres, I’m here to walk you through a comprehensive, nuanced usage-driven comparison of these two cameras. From sensor technology to autofocus, from ergonomics to video performance, I’ll share direct hands-on insights and technical analysis that you won’t find in spin-driven marketing fluff.

Let’s dive in.

Size and Ergonomics: Bulky Body Meets Pocket-Friendly Classic

When you pick these two cameras up, you’ll instantly notice how differently they approach form and handling.

Pentax K-5 II: This DSLR carries a mid-sized, solidly-built body at 760g, complete with a pentaprism optical viewfinder and decent heft that inspires confidence. The body dimensions of 131x97x73mm give it a clubby feel - perfect if you like a substantial grip that won’t easily get knocked about in an active shoot. It sports weather sealing, which is a significant plus for outdoor shooters braving unpredictable conditions.

Sony RX1: Meanwhile, the RX1 is a marvel of compact camera design at just 482g and 113x65x70mm. While it’s a “large sensor compact,” it feels closer to a premium rangefinder in handling than a traditional DSLR. No weather sealing and a more delicate build reflect its design priority - portability and stealth over rugged durability.

If you crave an all-weather, in-your-hands strong presence for long lens use or demanding environments, the Pentax wins ergonomics hands down. For street photographers, travelers, or anyone needing a pocketable powerhouse, the RX1’s compactness is a revelation.

Design & Control Layout: Clubs for Thumbs or Minimalist Elegance?

The control schemes couldn't be more different between these two.

Pentax K-5 II: The K-5 II gives you traditional DSLR clubs for thumbs. Physical dials for exposure compensation, shutter speed, ISO, and a top LCD status screen put instant control at the ready. It’s a tactile delight for those accustomed to quickly tweaking settings without diving into menus. Programmable buttons offer flexibility for preferred custom functions, and the pentaprism viewfinder ensures a bright, lag-free frame.

Sony RX1: The RX1 is minimalist in pursuit of compactness. You get fewer dedicated buttons and dials; many functions are menu-driven or rely on a single mode dial. There’s an optional electronic viewfinder accessory, but the default setup encourages live-view shooting on its 3-inch LCD. This stripped-back approach requires a slightly different workflow that rewards those comfortable with menus and slower adjustments.

For photographers who value immediate, manual controls - especially for fast-paced genres - Pentax’s physical dials reign supreme. But if ease of carry and minimalist design appeal, the RX1’s controls are cleverly optimized for discreet shooting.

Sensor Technology & Image Quality: APS-C Versus Full Frame, A Sensor Wars Story

This is where things get really interesting: an APS-C Pentax paired against a full-frame Sony.

Pentax K-5 II Sensor: Features a 16MP APS-C CMOS sensor (23.7x15.7mm) with a PRIME II processor. It employs a traditional Bayer filter array with an anti-aliasing filter. At DxOMark, it scores a respectable 82 overall, including a 23.8-bit color depth and 14.1 stops of dynamic range - a sweet spot for detailed landscapes and skin tone gradation.

Sony RX1 Sensor: Packs an imposing 24MP full-frame (35.8x23.8mm) CMOS sensor, also Bayer filtered with an AA filter. DxOMark awards it an overall 93 score, boasting 25.1-bit color depth and an impressive 14.3 EV dynamic range. Its low-light ISO performance is superb, nearly doubling the Pentax’s (2534 vs. 1235 at 18% SNR), due to a combination of physical sensor size, newer design, and processing.

Bottom line: with its larger sensor and higher megapixel count, the Sony RX1 offers superior image quality straight out of the gate - better resolution, cleaner high ISO shots, and richer color fidelity. That said, the Pentax K-5 II’s sensor holds up strongly against many APS-C competitors, delivering solid image quality that’s more than adequate for most web and print uses.

Image Processing and Autofocus: Prime II Magic Versus Contrast Focus Focused

Looking under the hood, autofocus and processing shape real-world shooting.

Pentax K-5 II: Its PRIME II processor may be “older tech” by 2024 standards but was cutting edge in 2013. It enables respectable continuous shooting of 7fps and supports phase-detection autofocus with 11 AF points, 9 of which are cross-type. The AF system includes face detection and tracking, even animal detection is missing (a downside). Autofocus in low light gets a little sluggish, but overall it’s reliable and direct. It also impresses with sensor-based image stabilization, a rarity in DSLRs of its class, helping sharpness in challenging conditions.

Sony RX1: Relies entirely on contrast-detection autofocus with 25 points but no phase detection. This choice reflects the RX1’s compact form and the limitations of its fixed lens system. While focus acquisition is accurate, it’s comparatively slower - especially for moving subjects. Continuous autofocus is absent, so wildlife or sports shooters may feel hamstrung. Continuous shooting is capped at 5fps, fewer than the Pentax.

For portraits, landscapes, and street photography, both cameras will autofocus competently, but for fast action or wildlife, Pentax’s phase-detection system outguns Sony’s contrast-only approach.

Build Quality and Weather Sealing: Can These Bodies Take the Heat?

If durability is on your checklist, the Pentax leads comfortably.

Pentax K-5 II: Offers extensive weather sealing against dust and moisture, ideal for rugged outdoor work. The sturdy magnesium alloy frame ensures solid reliability through rough environments and lots of use.

Sony RX1: No official weather sealing or rugged construction here. The build quality is excellent for a compact but lacks protection from the elements.

The takeaway: field photographers tackling unforgiving climates should lean on the Pentax. If you shoot mostly indoors or in controlled conditions, the RX1’s build won’t hold you back.

Handling the Interface: From Viewfinders to LCDs

No discussion is complete without addressing the user interface.

Pentax K-5 II: Sports a 3-inch fixed TFT LCD with 921k dots and an optical pentaprism viewfinder giving 100% coverage and 0.61x magnification. The viewfinder is bright, clear, and lag-free - preferred for critical manual focusing or fast action. The screen serves its purpose well but is not touch-enabled.

Sony RX1: Also has a 3-inch (albeit slightly higher resolution at 1229k dots) Xtra Fine TFT LCD optimized for live view framing. The RX1 offers an optional external optical/electronic hybrid viewfinder, but it’s bulky as an add-on. No touchscreen here either.

For those who swear by OVFs, the Pentax delivers higher usability out of the box. However, if you primarily shoot via LCD or appreciate higher live-view resolution, the RX1 displays are a bit more refined.

Lens Ecosystem and Flexibility: Giving Pentax a Big Advantage

The Pentax K-5 II supports the KAF2 mount with over 150 lenses available - vintage and modern - all suitable for various photographic needs from ultra-wide landscapes to macro close-ups.

Conversely, the Sony RX1 has a fixed 35mm f/2 lens - compact, sharp, and bright, but it means you’re locked into one focal length and aperture range (F2.0-22.0). This simplicity is a double-edged sword. It fosters creativity within constraints but sacrifices flexibility.

If your style requires swapping lenses - for portraits, wildlife, or macro - the Pentax’s extensive ecosystem is invaluable. The RX1 excels as a dedicated 35mm compact with stellar optics but isn’t a system camera.

Real-World Performance Across Photography Genres

Let’s get practical with how these two cameras handle specific photography styles and use cases.

Portrait Photography

The RX1’s full-frame sensor and 35mm f/2 lens produce beautiful bokeh and creamy subject separation, excellent for skin tones and flattering portraits. The higher resolution and color depth provide fine gradations in facial detail.

The Pentax K-5 II with its APS-C sensor and a compatible fast prime in the KAF2 lineup can also deliver excellent portraits, though the crop factor 1.5x changes framing dynamics (effective 50mm on a 35mm equivalent). The built-in stabilization helps in low light, while its reliable phase-detection AF locks onto eyes and faces well.

Landscape Photography

Pentax’s weather sealing and higher burst speed (for bracketed exposures) make it more practical in the field. Combined with dynamic range of 14.1 stops, you can capture wide tonal ranges, although not quite as much as the RX1 at 14.3 stops.

The RX1’s full-frame sensor shines in landscape detail and cleaner shadows. Its fixed 35mm lens provides a natural wide-angle field of view, but its lack of weather sealing is a limitation outdoors.

Wildlife and Sports Photography

Here the Pentax is better suited overall due to faster 7fps burst rates, phase-detection AF with cross points, and weather sealing. The RX1’s 5fps and contrast AF struggle tracking fast subjects, plus the limited lens focal length restricts reach.

Street and Travel Photography

The RX1 stands out due to its small size, discreet design, and excellent image quality. Its 35mm lens is a classic focal length for street shooters. Despite fewer controls, its portability and silent operating nature make it ideal for candid moments.

Pentax’s larger body and heft do weigh on discretion and portability, but it offers greater control and battery life (980 shots vs. RX1’s 270).

Macro and Close-up

Neither camera specializes in macro without additional lenses or accessories. Pentax’s mount allows macro lenses; the RX1 has limited options, though its lens focuses reasonably close for general close-ups.

Night and Astrophotography

The RX1’s superior high ISO performance is a clear advantage here, allowing cleaner long exposures at higher sensitivities. Pentax’s stabilization helps reduce shake but noise will be higher beyond ISO 1200.

Video Capabilities: Basic and Functional Versus Slightly More Flexible

Both cameras offer Full HD 1080p recording, but they differ in nuances.

Pentax K-5 II: Shoots 1920x1080 at 25fps using Motion JPEG format. Offers microphone input but no headphone jack. Lacks 4K or advanced video features.

Sony RX1: Supports 1080p at 60, 50, 25, and 24fps with MPEG-4 and AVCHD formats, enabling smoother motion capture. Also includes microphone input but no headphone monitoring. No image stabilization means handheld needs care.

For casual video, the RX1 has a slight edge with frame rates and codecs, but neither camera targets videographers.

Battery Life, Storage, and Connectivity: The Practicalities of Use

Pentax’s D-LI90 battery offers roughly 980 shots per charge, catering to full-day shoots without spares. Sony’s NP-BX1 barely hits 270, forcing you to carry multiple spares.

Both cameras rely on single SD card slots, with Sony’s RX1 adding compatibility with Memory Stick formats.

Connectivity is basic on both - no Bluetooth or WiFi on Pentax, only Eye-Fi compatibility (wireless SD cards) on Sony. Both have HDMI and USB 2.0 ports but no modern 5GHz WiFi or USB-C.

Pricing and Value Assessment: Cheapskate or Premium Splurge?

The Pentax K-5 II retails around $830 (body only), offering rugged reliability, extensive lens support, and respectable image quality for a relatively modest investment.

The Sony RX1 demands a hefty premium at roughly $2800 - a price-conscious buyer’s nightmare - but you’re paying for a compact, high-end full-frame experience and exceptional optics.

If you want the highest image quality in a pocketable form and don’t mind spending, the RX1’s price is justified. For those budget-sensitive or preferring a system camera with more lenses and weatherproofing, the Pentax K-5 II delivers strong bang-for-your-buck.

Sample Image Gallery: See It to Believe It

If you want to get a sense of what these cameras produce in the real world, here’s a handy side-by-side samples gallery from both cameras showcasing portraits, landscapes, and more.

Pentax K 5 II front Pentax K 5 II screen back Sony RX1 front Sony RX1 screen back

Performance Ratings: How They Stack Up Overall

DxOMark’s standardized testing gives us an authoritative benchmark:

• Sony RX1 clearly outpaces Pentax K-5 II in sensor performance scores, low light ISO, and color depth.
• Pentax K-5 II scores consistently well within APS-C DSLR territory but falls short of full-frame offerings.

Specialized Genre Performance: Which Camera Shines for Your Style?

Breaking it down to genre points, here’s where each camera excels or struggles.

• Wildlife & Sports: Pentax leads (continuous AF & burst)
• Portraits & Landscapes: Sony edges out (sensor size, color fidelity)
• Street & Travel: Sony wins for discretion and portability
• Macro: Pentax more versatile with lenses
• Night/Astro: Sony better low noise and ISO
• Video: Sony more versatile frame rates

Final Verdict: Who Should Buy What?

Choose the Pentax K-5 II if you:

• Need a weather-sealed, rugged DSLR for outdoor work
• Want access to a huge lens ecosystem with specialized optics
• Prefer full manual controls and optical viewfinder immediacy
• Shoot action, wildlife, or sports requiring fast AF and burst
• Are budget-conscious but don’t want to compromise durability
• Value longer battery life for extended shoots

Go for the Sony RX1 if you:

• Crave the absolute best image quality in a compact form factor
• Prioritize portability, street shooting, travel, or daily carry
• Shoot mostly portraits, landscapes, or casual low-light work
• Don’t mind the single fixed lens and limited burst speed
• Want the flexibility of HD video at multiple frame rates
• Can absorb the higher price point as a worthy premium for quality

To wrap up, both the Pentax K-5 II and Sony RX1 hold up brilliantly in their respective niches, reflecting design choices that serve very different photographers. Your best pick hinges on what you shoot, how you shoot, and which compromises you’re willing to accept. As someone who’s pushed both cameras through varied environments and lighting, I can confidently say: you really can’t go wrong, provided you’re clear on your priorities.

Happy shooting!