Pentax 645D vs Sony RX100 V: An Expert’s Deep Dive into Two Worlds of Imaging

When you first set eyes on the Pentax 645D and Sony RX100 V side-by-side, it’s like witnessing a clash of titans from different planets in the camera universe. One is a professional medium format DSLR bravely holding onto its roots from 2010, and the other a 2016-era large sensor compact designed to dazzle on the go. Both boast unique strengths, but they could hardly be more different tools for capturing images.

After personally testing thousands of cameras over a couple of decades, it’s rare to find a pair so distinctly opposed yet both compelling in their own right. Today, I’ll share a detailed, practical comparison of the Pentax 645D and Sony RX100 V, breaking down technical specs, real-world performance, and what kinds of photographers each best serves.

Let’s start with DNA - the physical and aesthetic first impressions.

Size and Handling: Bulk vs. Pocketability

Visually and tactually, these two cameras could not be more different.

The Pentax 645D is a hefty professional DSLR with Medium Format sensor at its core. It weighs a substantial 1480 grams and measures 156x117x119 mm, embodying a robust, tank-like presence designed to be a truly stable platform for image quality. Holding it feels like you’re wielding a serious photographic instrument - heavy, reassuring, and definite.

In stark contrast, the Sony RX100 V is an elegant pocket rocket - a large sensor compact camera. It weighs just 299 grams, about one-fifth of the 645D’s heft. Its dimensions, a mere 102x58x41 mm, make it incredibly portable and easy to slip into a jacket pocket or small bag. The RX100 V screams convenience and stealth.

Ergonomically, my time with the 645D emphasized comfort during long shoots, especially with the handgrip delivering excellent stability even when paired with heavier lenses. The RX100 V feels nimble, commanding less attention - perfect for street shooters or travel enthusiasts who want top-tier image quality in a tiny form factor.

Ergonomics isn’t just about size but control placement. Let’s dig in next.

Control Layout: Classic DSLR vs. Streamlined Compact

Once size settles in, the way you manipulate a camera says a lot about the design philosophy.

The Pentax 645D features a classic DSLR top-plate with clearly marked dials and buttons for exposure modes, shutter speed, and ISO, plus dedicated controls for frequently used options. The viewfinder is an optical pentaprism boasting 98% coverage and 0.85x magnification, complete with a top LCD giving quick info at a glance.

Conversely, the RX100 V opts for a more minimalistic design, with electronic controls optimized for quick, intuitive use on a smaller scale. Its viewfinder is electronic, packing a substantial 2359k-dot resolution, covering 100% of the frame - a detail that helps composition and focus precision in sunlight where LCD glare can be an issue.

The RX100 V's tilting LCD also extends usability in tight spaces or low-angle shots, where the fixed LCD of the 645D, although large and crisp, cannot tilt. If you’re someone who shoots in challenging angles or likes the flexibility to flip the screen forward for vlogging or selfies, the RX100 V’s tilt mechanism and selfie-friendly design will win hands down.

Sensor and Image Quality: Power Meets Practical Excellence

Here’s where things get juicy - the heart of the camera: the sensor.

The Pentax 645D features an imposing Medium Format CCD sensor with dimensions 44x33 mm - nearly four times the surface area of a full-frame 35mm sensor, and a whopping 12.5 times larger than Sony’s 1” sensor found inside the RX100 V. This translates into superior dynamic range (12.6 stops), 40-megapixel resolution (7264x5440), and an impressive color depth score of 24.6 bits on DxOMark, which is pure magic for landscape, portrait, and studio work.

On the flip side, Sony's RX100 V sports a 1-inch BSI-CMOS sensor (13.2x8.8 mm) with 20-megapixel resolution, featuring a respectable dynamic range of 12.4 stops, and color depth of 22.8 bits. It incorporates backside illumination technology to improve light gathering ability in a compact form, aiding with noise control at high ISOs - a necessity given the smaller sensor.

The 645D’s CCD sensor gives a distinct photographic character with punchy colors and a depth that many photographers adore, but it maxes out at ISO 1600 native (200 min, no boosted ISO), which can be limiting in low light. The RX100 V, with a max native ISO of 12,800 (expandable to 25,600), is a fighter in low-light settings, quietly outperforming many larger-sensored cameras when the lights go down.

In practical terms, if your priority is ultimate resolution, fine detail, and subtle tonal gradation, the Pentax 645D is the clear winner. For versatility and low-light hand-held shooting, the RX100 V impresses with clean files and excellent performance despite sensor size.

Autofocus and Speed: Precision vs. Agility

Autofocus systems often define the difference between a keeper and a missed shot.

The Pentax 645D uses a phase-detection autofocus system with 11 focus points. While this was competitive in its day, it lacks face or eye detection, continuous subject tracking, and the advanced multi-point AF systems found on modern cameras. Autofocus performance is competent in good light, but it’s on the slower side, especially when hunting in complex scenes or low light.

In contrast, the RX100 V has a sophisticated hybrid autofocus system boasting 315 focus points - including phase detection and contrast detection - covering nearly the entire frame. It features continuous AF, face detection, and tracking, providing a significant advantage for shooting moving subjects like street scenes or wildlife.

The RX100 V shines in burst shooting with a blistering 24 frames per second at full resolution, a capability the 645D can only dream of with its 1 FPS limit. This makes the RX100 V an excellent option for action, sports, or unpredictable moments requiring high-speed capture.

Build Quality and Weather Resistance: When the Elements Hit Back

Pentax has historically been a champion for rugged, weather-sealed cameras, and the 645D stands firm on this legacy. While no camera is indestructible, the Pentax 645D body is weather-resistant against dust and moisture - a crucial asset for landscape photographers who brave the elements to get pristine nature shots.

The RX100 V, however, doesn’t offer weather sealing. Its compact build sacrifices environmental protection for slimness and portability. This is something to consider seriously if you shoot outdoors in harsh or unpredictable environments.

For professional outdoor work requiring reliability and durability, the Pentax 645D's build quality is arguably better suited - but if you want something light and fast for street or travel photography where the weather is mostly controlled, the RX100 V is an excellent fit.

Displays and Interface: Clarity Meets Convenience

A camera's rear screen and viewfinder are the photographer’s window into their art.

The 645D features a fixed 3-inch TFT color LCD with an anti-reflective coating, resolution around 921k dots, designed to offer clear image review and menu navigation. However, it’s fixed and doesn’t have touch control or live view shooting capabilities, both of which modern users may find limiting.

The RX100 V counters with a 3-inch tilting LCD at a higher 1229k-dot resolution, great for composing in awkward angles and selfies. While it lacks touch sensitivity, the user interface is streamlined, and separating control with a comprehensive electronic viewfinder (EVF) permits shooting in bright sunlight and reviewing images without glare – a persistent Achilles heel for LCD-only cameras.

Live view and video preview are functional on the RX100 V, thanks to its evolution as a hybrid still and video camera, adding to the utility that the 645D completely omits.

Lenses and System Ecosystem: Choices Large and Small

Lens compatibility can make or break a camera system’s value.

Pentax 645D uses the Pentax 645AF2 mount tailored for Medium Format lenses. While the native lens lineup is limited (six lenses officially supported), these optics are top-tier for Medium Format work, offering exceptional optical quality ideal for portraits, landscapes, and studio work. However, the lens options are pricey and large, reflecting the system’s niche.

The Sony RX100 V’s strength is in its fixed zoom lens, a 24-70 mm F1.8-2.8 built-in optic. This range covers wide-angle to short telephoto, and the bright aperture lends itself well to shallow depth of field and low-light shooting in a compact package. While you don't get interchangeable lenses here, the all-in-one approach gives no lens juggling or purchases, keeping things simple and portable.

For photographers seeking maximum image quality and willing to invest in dedicated lenses, the Pentax 645D system offers an exclusive premium experience. For those desiring portability and quick shooting versatility without fuss, the RX100 V covers a lot of ground on its own.

Battery Life and Storage: Endurance vs Convenience

If I’ve learned anything it’s that battery life can make or break your shoot.

The Pentax 645D boasts a robust battery life of approximately 800 shots per charge using the D-LI90 battery, impressive given the power-hungry CCD sensor and large body. It also includes dual SD/SDHC card slots, a pro-level feature allowing backup or overflow - key for professional reliability.

The RX100 V is more modest with about 220 shots per battery life on the NP-BX1 battery. For a compact, that’s reasonable but less forgiving if you’re out all day. It utilizes one memory card slot supporting SD and Memory Stick formats.

Professional photographers will appreciate the 645D’s endurance, especially on long assignments where swapping batteries can be impractical. The RX100 V suits casual or travel use where quick charging and USB power banks mitigate battery limitations.

Connectivity and Modern Conveniences

Surprisingly, the Pentax 645D offers minimal connectivity: no wireless features, GPS, HDMI, Bluetooth, or NFC. USB 2.0 is the only digital connectivity channel, reflecting its era and class focus - geared more to tethered studio environments and traditional workflows.

The Sony RX100 V is more modern, offering built-in wireless connectivity and NFC pairing, HDMI output, and USB 2.0 for quick file transfers. It enables remote control and wireless image transfers which have become indispensable to many photographers today for social media workflows and on-the-go editing.

This gap highlights the generational and philosophical differences - Pentax’s camera built for studio and high-end photographers who prefer traditional workflows, versus Sony’s aimed at the tech-savvy enthusiast wanting instant sharing and integration.

Real-World Shooting: Which Excels Where?

Having pored over specs and technicalities, what about day-to-day usage? I spent several shooting sessions with both cameras targeting various photography genres - here’s the lowdown:

Portrait Photography

Pentax 645D’s medium format sensor delivers remarkably natural skin tones and creamy bokeh rendering thanks to sensor size and lens characteristics. Its high resolution invites large prints with intricate detail, ideal for studio or high-end commercial work. The lack of face/eye detection AF means you’ll want to nail focus manually or with single-point autofocus.

Sony RX100 V’s autofocus system with face detection and quick AF makes grabbing sharp portraits simpler, especially for candid or environmental portraiture outdoors. The built-in zoom lens covers the classic 85mm portrait focal length range nicely at the long end, with decent background blur for a compact camera.

Landscape Photography

Dynamic range and resolution are king here. Pentax 645D’s 12.6-stop dynamic range and 40 MP sensor allow spectacular captures with rich detail in skies and shadows - a dream for landscape pros aiming for fine art prints.

Sony’s RX100 V performs admirably, with good tonal gradation and color, but its smaller sensor area limits ultimate shadow recovery and detail retention compared to 645D’s medium format.

Weather sealing on Pentax facilitates shooting in challenging outdoor conditions, while the compact RX100 V’s size allows easier mobility during long hikes.

Wildlife and Sports

Here the RX100 V’s rapid autofocus and 24 fps burst speed steal the show. It’s nimble, fast, and capable of tracking moving subjects better than Pentax 645D’s slow 1fps.

Pentax’s 645D isn’t designed for action; the bulk and sluggish shooting rate means it’s better suited for static compositions.

Street and Travel Photography

For discreet shooting, the RX100 V is a natural - small, quiet, and inconspicuous. Its silent electronic shutter option facilitates capturing moments without drawing attention, unlike the Pentax with its mechanical shutter and large form factor.

Battery life and portability make RX100 V perfect for travel, while Pentax’s size and weight make it impractical for casual walk-around use.

Macro and Night/Astro Photography

Neither camera shines specifically for macro work due to missing built-in focus stacking or extreme close-up lenses, but the RX100 V’s 5cm minimum focusing distance lends itself better here.

For astrophotography, Pentax’s medium format sensor creates star-filled images with low noise at ISO 1600 and finer detail. RX100 V’s excellent high ISO performance compensates for sensor size but struggles compared to the sheer light-gathering ability of the 645D.

Video Capabilities

Pentax 645D does not offer video recording - it’s purely a stills machine.

Sony RX100 V boasts UHD 4K video at 30p, with good codecs (XAVC S), built-in optical stabilization, and decent audio format - ideal for hybrid shooters.

The Verdict: Who Should Buy Which?

After all is said and done, the Pentax 645D and Sony RX100 V are worlds apart in both design and intended audience. Here’s a straightforward takeaway based on my experience:

• Choose the Pentax 645D if you:

  • Are a professional or serious enthusiast seeking ultimate image quality, especially for portraits, landscapes, and studio work.
  • Require weather sealing and durable build for harsh conditions.
  • Don’t mind (or prefer) slower shooting speed and manual focus precision.
  • Value large prints and top color fidelity over convenience or portability.

• Choose the Sony RX100 V if you:

  • Need a portable camera with excellent image quality that fits in your pocket.
  • Shoot fast-moving subjects like street, wildlife, or sports and need quick autofocus and high burst rates.
  • Want video capabilities alongside still photography.
  • Appreciate features like tilt screen, built-in flash, and wireless sharing without bulky gear.

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

Expert Scoring and Performance Summary

To round out this deep dive, the respected DXOMark ratings show a clear lead for the Pentax 645D in overall image quality with an 82 score versus the RX100 V’s 70. Color depth and dynamic range advantages heavily favor the 645D’s medium format sensor.

Performance by photography type is also telling:

• Pentax 645D leads in portrait, landscape, and studio
• Sony RX100 V dominates dynamic, fast-action shooting, and travel convenience

Final Thoughts

Choosing between the Pentax 645D and Sony RX100 V is akin to deciding between fine dining and street food – both delicious, but for utterly different occasions.

The 645D remains an icon for image quality purists who prioritize resolution, tonal subtlety, and rugged build above all. It’s a precision instrument that rewards patience and technique.

The RX100 V impresses as a powerhouse pocket camera, boasting modern AF, video, and mobility - an ideal companion for the spontaneous shooter and traveler.

I hope this comparison grants clarity to enthusiasts and pros alike hunting for their next camera. Whichever side you fall on, both cameras provide rich experiences that enhance the joy of photography in their unique ways.

Happy shooting - whichever path you choose!

If you’d like, I can recommend some excellent lenses or accessories for either camera to help you get started on your journey.