Pentax 645Z vs Sony RX100 V: A Deep Dive by a Veteran Camera Tester

As someone who's spent over 15 years testing hundreds of cameras - from medium format workhorses to pocket-sized super-compacts - I was thrilled to sit down and put the Pentax 645Z and Sony RX100 V head-to-head. These two couldn’t be more different at first glance: one is a robust medium format DSLR, the other a compact large-sensor point-and-shoot. Yet both hold passionate followings and serve divergent yet intersecting photographic ambitions.

In this comprehensive comparison, I’ll walk you through every major photography discipline and use case, backed by hands-on experience and technical rigor. You’ll get authentic insight into how these cameras perform across portraiture, landscapes, wildlife, sports, macro, night shooting, video work, travel practicality, professional workflow, and more. Plus, I’ll analyze ergonomics, autofocus, sensor tech, battery life, lens ecosystems, and price-to-performance - all helping you make the smart choice tailored to your style and budget.

Let’s kick off by sizing up their physical presence, which often sets the tone for how a camera feels in practice.

Size and Ergonomics: Medium Format vs Pocket Power

Handling the Pentax 645Z immediately reminds me of carrying a professional medium format camera that demands respect. It’s a sizable and weighty beast: 156 x 117 x 123 mm and a solid 1550 g. The body feels rock-solid and built to endure tough shooting conditions. The 645Z’s grip is generous, designed for stability during long shoots or with heavy lenses.

In contrast, the Sony RX100 V’s 102 x 58 x 41 mm and 299 g frame redefines portability. It slips into nearly any jacket pocket or bag compartment with ease. This camera screams discreet, quick-capture capability. Its metal chassis feels premium yet lightweight, making it perfect for street or travel photographers who favor spontaneity.

From my years testing, the Pentax is an investment in presence and endurance, great if you anticipate landscapes, studio work, or pro gigs that prioritize handling over stealth. The Sony shines in mobility and instant readiness, ideal for shooters on the move or those seeking a high-caliber compact companion.

Design and Control Layout: Intuitive or Minimalist?

Looking down at the top controls, the Pentax 645Z shows its professional DSLR heritage: dedicated dials for shutter speed, ISO, and exposure compensation, plus well-placed function buttons. These tactile controls create a workflow that can be second nature to experienced shooters who want minimal digging through menus. The tilting 3.2" LCD and pentaprism optical viewfinder provide versatility in composition, although the OVF only covers 98% of the frame - a minor downside but worth keeping in mind for pixel-peepers.

Sony’s RX100 V offers a more stripped-back, minimalistic interface optimized for compact use. The absence of an articulated touchscreen is a little dated, though the tilting screen is bright and sharp with 1229k dots. Its electronic viewfinder packs higher resolution (2359k dots) and 100% coverage, delivering precise previewing despite the smaller magnification. Controls lean heavily on the control wheel and function buttons, which can feel non-intuitive at first, especially if you’re accustomed to more physical dials.

In practice, I appreciated the Pentax for deliberate shooting sessions and the Sony for scenarios demanding quick adjustments on-the-fly, though neither offers touchscreen advantages which some modern rivals include.

The Heart of the Image: Sensor Size and Image Quality

Here lies the most profound difference - sensor size. The Pentax 645Z is a bona fide medium format camera, sporting a 44 x 33 mm CMOS sensor with a whopping 51 MP resolution (8256 x 6192). This sensor dwarfs the Sony RX100 V’s 1" BSI-CMOS at 13.2 x 8.8 mm and 20 MP (5472 x 3648). The difference in sensor area is a staggering 1452 mm² vs 116 mm² respectively, directly influencing image quality potential.

From my controlled lab and real-world testing:

• Dynamic range: Pentax’s 645Z delivers an outstanding 14.7 EV, allowing remarkable highlight retention and shadow recovery even in toughest lighting. Sony’s RX100 V performs admirably for its class at 12.4 EV, but naturally can’t match the latitude and refinement of medium format.

• Color depth: Pentax’s 26-bit color depth translates into smoother tonal gradations - especially visible in landscape skies and skin tones. The Sony’s 22.8-bit depth is strong for a compact, but occasionally shows minor posterization in subtle texture transitions.

• Low light ISO: The 645Z feels like a revelation. Its ISO native range spans 100–204,800 (!) and despite the high pixel count, noise at ISO 4500 and above can be cleanly managed, thanks to larger pixels and advanced PRIME III processing. Sony’s RX100 V maxes out at ISO 12,800 (boosted 25,600) and while BSI-CMOS tech enhances low-light sensitivity, noise is noticeably more apparent above ISO 1600.

These figures reflect what I’ve encountered shooting nightscapes, portraits, and wildlife: the Pentax produces breathtaking images that rival studio lights even under submissive ambient conditions, while the Sony remains a capable performer for handheld low-light snaps but with trade-offs.

Eye and Autofocus Performance: Precision vs Speed?

The Pentax 645Z uses a hybrid autofocus system with 27 focus points and phase/contrast detection. While phase detection helps speed up initial focus acquisition, Pentax’s traditional AF system is somewhat conservative compared to mirrorless rivals. Notably, it lacks advanced animal-eye detection and multi-area AF is limited.

In the field, this camera excels in discerning focus accuracy for portraits and landscapes, with good face detection, but struggles to keep up under fast-action or erratic wildlife scenarios. The continuous shooting rate of 3 fps is modest and narrows its utility for high-speed bursts.

The Sony RX100 V boasts an extensive 315-point phase-detection AF system integrated across the sensor, supported by sophisticated autofocus algorithms. I found its tracking capability exemplary for a compact, locking onto moving subjects with agility and reliable face detection. Eye AF, while only for humans and without animal-eye support, performs capably, assisting in portrait shoots on the go.

The RX100 V’s burst shooting at 24 fps with continuous AF tracking is blisteringly fast for capturing fleeting moments - ideal for sports or street photography where timing is everything.

Portrait Photography: Rendering Beauty and Character

When focusing on portrait work, both cameras serve distinct needs.

The Pentax 645Z’s medium format sensor enables exquisite skin tone gradations. The lack of an anti-aliasing filter boosts sharpness while retaining natural texture, making portraits luminous and lifelike under studio or natural settings. Paired with Pentax 645AF2 lenses famed for buttery bokeh, this system captures eyes with surgical precision, accentuating their sparkle without over-sharpening.

The RX100 V, with its 24–70mm f/1.8-2.8 equivalent lens, offers respectable shallow depth of field and creamy background separation - impressive for a compact. The autofocus locks quickly onto faces, smoothing skin textures somewhat via internal processing, which I noticed can make it a good ‘social media’ shooter. However, the smaller sensor limits highlight roll-off and subtle skin tone nuances - especially in challenging lighting.

Use the RX100 V for environmental portraits or snapshots where mobility overrides ultimate image quality. Choose the Pentax for professional or artful portraiture demanding maximum detail and control.

Landscape Photography: Dynamic Range and Weather Durability

The Pentax 645Z shines for landscape photographers who need the full tonal palette and rugged build. Its highly weather-sealed body survives freeze and dust exposure impressively - a must when I’ve taken it to alpine locations with unpredictable conditions.

The exceptional dynamic range combined with 51 MP resolution enables large prints with incredible clarity and detail. Landscape shooters benefit from the manual exposure modes, exposure bracketing, and the ability to tether files for post-processing flexibility.

The RX100 V’s compactness is a strength on travel hikes and urban panoramas, but it lacks environmental sealing and the resolution to produce gallery-sized prints. Dynamic range is decent but can clip highlights in harsh sunlight, requiring careful exposure or post-processing correction.

Neither camera offers in-body stabilization on the Pentax, where I rely on sturdy tripods, while the Sony’s optical stabilization helps handheld landscape or cityscapes during slower shutter speeds.

Wildlife and Sports Photography: Speed and Agility

Given its medium format lineage, the Pentax 645Z struggles with speed. Its 3 fps burst and AF system are better suited for deliberate manual focus or slower-moving animals. The limited autofocus coverage and lack of animal-eye detect mean you’ll need patience and skill rather than autofocus wizardry.

On the other hand, the Sony RX100 V amazes for a compact: 24 fps continuous shooting and 315-point autofocus track fast trains of athletes or errant birds with remarkable precision. Its silent electronic shutter option reduces shutter noise - helpful in wildlife situations.

For professionals chasing action, the RX100 V is surprisingly agile, though its sensor size limits ultimate image quality. The Pentax is better as a targeted wildlife landscape tool, especially when absolute image quality takes precedence.

Street and Travel Photography: Discretion or Presence?

The Sony RX100 V’s diminutive size, quieter shutter, and tilting screen make it a champion of candid street and travel photography. Its excellent autofocus speed aids quick captures, and built-in Wi-Fi connectivity (with NFC) facilitates immediate image sharing - a modern traveler’s dream.

The Pentax 645Z is decidedly more cumbersome and conspicuous. Its weight and size make it less ideal for long roaming sessions or spontaneous street shots. The absence of wireless and touchscreen controls is a disadvantage when immediate sharing or rapid interface access is useful.

Battery life favors the Pentax though: rated for 650 shots per charge versus the Sony’s 220. Consider packability and stamina vs image fidelity when deciding here.

Macro, Night, and Astro Photography: Precision and Sensitivity

The Pentax’s sensor size, combined with its viable minimum shutter speed (down to 30 seconds) and excellent dynamic range, produces exceptional night and astro photos. I’ve enjoyed astrophotography sessions with this camera capturing detailed star fields, helped by manual exposure controls and a low native ISO base of 100. The lack of in-body stabilization places more emphasis on sturdy support gear.

Sony’s RX100 V allows close focusing at 5 cm, delivering satisfying macro detail for a compact, but its sensor size and lens limit ultimate magnification and shallow depth effects. Night gear aficionados will find respectable performance at ISO 1600–3200, but it cannot rival medium format noise handling or dynamic range. However, the RX100 V’s electronic shutter speeds up to 1/32,000s offer creative exposure flexibility and silent shooting for sensitive environments.

Video Features: 4K vs Full HD and Stabilization

Surprisingly, the Pentax 645Z only offers Full HD video (up to 1920x1080 at 60i), without 4K capabilities. Audio quality benefits from a microphone input, but no headphone jack limits monitoring precision on set. With no in-body stabilization, handheld video demands external aids like gimbals.

Conversely, the RX100 V captures 4K UHD at 30p (though slightly cropped), with XAVC S codec providing excellent bitrates. Optical image stabilization stabilizes handheld footage impressively, and its built-in flash can double as fill light during run-and-gun shoots. Microphone input is absent but many casual videographers find built-in mic adequate.

For professional videographers, Pentax is limited; for vloggers and hybrid shooters prioritizing video, Sony’s RX100 V is the clear winner despite microphone peripherals limitations.

Build Quality, Weather Sealing, and Durability

Pentax’s hallmark is toughness: dustproof, freezeproof, and well weather sealed, the 645Z withstands harsh environments, making it invaluable for fieldwork. Its glass-reinforced body and ergonomic grips instill confidence during extended shoots.

Sony RX100 V, while solidly built with premium materials, lacks official environmental sealing. This means photographers must carefully protect it in inclement conditions - something I take care to remember on humid or rainy travels.

Your shoot locations and expected conditions weigh heavily when choosing here.

Lens Ecosystem and Compatibility: Versatility or Fixed?

The Pentax 645Z’s medium format 645AF2 mount opens doors to an array of dedicated medium format lenses - from prime portraits to wide-angle landscapes. This system flexibility profoundly influences the quality and shooting experience. I’ve had excellent results pairing the 645Z with specialized lenses offering creamy bokeh and sharp corners - a rarity for a compact system.

Sony RX100 V has no interchangeable lenses. Its built-in 24-70mm equivalent zoom is impressively versatile for a pocket camera but can’t be swapped for specialized optics. This is a logical tradeoff for portability but limits ultimate creative reach and optical quality enhancements.

Battery Life and Storage: Longevity vs Convenience

Pentax’s D-LI90 battery outperforms the RX100 V’s NP-BX1, comfortably delivering about 650 captures per charge compared to 220. This advantage shines on long trips or shoots without nearby charging options.

Storage is also better managed on the Pentax with dual SD/SDHC/SDXC slots, offering redundancy or extended storage space. Sony’s single slot supports SD and Memory Stick formats, acceptable but a slight limitation for professionals.

Connectivity and Wireless Features

Wireless connectivity is a structural weakness for the Pentax - there is no built-in Wi-Fi or Bluetooth, and GPS is optional via external accessories. In our fast-paced digital sharing world, this can be a bottleneck.

Sony’s RX100 V includes NFC and Wi-Fi, easing smartphone pairing, wireless image transfer, and remote shooting. This reflects its role as a hybrid street/travel device aiming for immediacy.

Price-to-Performance: Who Gets More Bang for the Buck?

Pentax 645Z’s price hovers north of $5000, targeting advanced enthusiasts and professionals willing to invest in uncompromising image quality and durability. The costs of lenses and accessories are similarly high but justified by medium format output.

Sony RX100 V retails near $1000, an excellent value for photographers seeking a premium compact with strong autofocus, excellent video, and good image quality in a portable package.

Real-World Sample Images: Seeing Is Believing

Pentax 645Z front Pentax 645Z screen back Sony RX100 V front Sony RX100 V screen back

Comparing raw sample shots under controlled conditions reveals the pigeonhole nature of these two cameras. The 645Z delivers stunning detail with buttery smooth gradients in portraits and impeccable textures in landscapes. Meanwhile, the RX100 V excels in quick street snaps, delivering color-accurate JPEGs straight out of the camera suitable for everyday sharing without extensive post-processing.

Camera Scores Across Genres: A Clear Contrast

Putting these cameras side-by-side through the lens of genre scores:

• Portrait: Pentax dominates with color depth and bokeh control.
• Landscape: Pentax leads on resolution and weather sealing.
• Wildlife & Sports: Sony RX100 V outpaces with autofocus and burst speed.
• Street & Travel: Sony’s compact size and connectivity win hands down.
• Macro: Pentax’s lenses offer more precision but Sony’s close focusing lens is surprisingly capable.
• Night/Astro: Pentax has the edge due to sensor size and noise control.
• Video: Sony is superior thanks to 4K and stabilization.

Final Thoughts: Who Should Buy Which?

I want to be transparent - I have no affiliations with Pentax or Sony, but I have thoroughly tested both cameras using standardized lab charts, in the field, and across varied lighting conditions over weeks.

• Choose Pentax 645Z if:

  • You demand top-tier image quality for portraits, landscapes, or fine art.
  • You need a durable, weather-sealed camera designed for harsh conditions.
  • You value medium format sensor size and interchangeable lenses.
  • You prefer a camera more suited for controlled shooting at events, studio, or nature expeditions.
  • Budget is flexible and image excellence is your top priority.

• Choose Sony RX100 V if:

  • You want a powerful all-in-one compact that fits in your pocket.
  • You shoot fast-paced subjects - street, travel, sports - where speed and agility matter.
  • You need strong autofocus, 4K video, and wireless connectivity.
  • You prioritize convenience, portability, and video capabilities alongside solid image quality.
  • You seek an affordable, accessible camera with excellent lens quality for a fixed zoom.

Summary

The Pentax 645Z and Sony RX100 V may inhabit different photographic worlds but each excels within its sphere. The 645Z is a medium format titan - slow but sublime in quality and endurance - while the RX100 V is a master-class compact that delivers versatility, speed, and instant gratification.

When deciding, ask yourself: do you want the ultimate image fidelity and hands-on control? Or a pocket-sized dynamo that keeps pace with your fast-moving lifestyle? Both cameras reward careful users; the right one depends on your unique creative path.

For photographers who value expertise and trust firsthand testing insights, I hope this thorough comparison helps you confidently select your next camera companion.

Happy shooting!

All images are used with permission and provide visual context to the in-depth technical and experiential discussions.