Panasonic GX850 vs Pentax 645D: A Comprehensive Comparison for Enthusiasts and Professionals

In an era where camera technology spans from lightweight entry-level mirrorless models to colossal medium-format DSLRs, discerning photographers often face complex choices. The Panasonic Lumix DMC-GX850 and the Pentax 645D embody two ends of that spectrum. Despite both bearing the camera moniker, these machines cater to fundamentally different objectives, user skill levels, and practical shooting scenarios.

Drawing upon years of extensive, hands-on evaluations of thousands of cameras, this article offers a rigorous, methodical comparison revealing their strengths and limitations. The goal is to clarify the real-world usability, performance nuances, and technical capabilities of these two cameras. Our emphasis is on measurable, experience-backed attributes to empower enthusiasts and professionals to make informed purchasing decisions aligned with their precise photographic discipline and workflow.

First Impressions: Size, Handling, and Ergonomics

Physical design and handling markedly influence shooting comfort and operational effectiveness. The Panasonic GX850 is a compact, rangefinder-style mirrorless camera weighing just 269 grams with dimensions of 107x65x33 mm, designed with portability in mind. Conversely, the Pentax 645D is a substantial professional DSLR, tipping the scales at 1480 grams and measuring 156x117x119 mm, built for robust use in demanding environments.

The GX850’s minimal footprint is ideal for travel photographers, street shooters, and casual users who prioritize inconspicuousness and ease of carry. It fits comfortably in one hand with intuitive thumb placement on the rear touchscreen. However, its compact form factor sacrifices physical controls and grip bulk, which can challenge prolonged handheld sessions or rapid adjustments under pressure.

By contrast, the 645D’s pronounced heft and ergonomic contours offer excellent stability, especially when paired with heavy medium-format lenses. Its traditional DSLR layout accommodates large buttons and dials easily operated with gloves or in adverse conditions. The solid build integrates weather sealing, further enhancing dependability for landscape and studio photographers who subject their gear to the elements.

Design Philosophy: Control Layout and Interface

Control intuitiveness and interface design shape user engagement and productivity during shoots. The GX850 employs a modern interface with a tilting 3-inch touchscreen as its control centerpiece and offers minimal dedicated physical buttons.

The lack of a dedicated viewfinder and reliance on the screen alone may impede framing in bright outdoor environments. That said, touchscreen AF point selection and gesture navigation provide a responsive experience for casual and enthusiast users prioritizing simplicity. Customization options are limited, though exposure compensation, aperture, and shutter priority modes are supported.

The Pentax 645D’s professional DSLR heritage reveals itself in an array of physical controls, including a top plate LCD for quick status monitoring, mechanical dials for shutter speed and exposure compensation, and a pentaprism optical viewfinder covering 98% of the frame at 0.85x magnification.

The absence of a touchscreen may displease some, but the interface offers immediate feedback and tactile precision highly valued by studio and medium-format photographers. Its design complements deliberate, methodical shooting styles emphasizing manual exposure control and lens adjustment.

Sensor Technology: Size, Resolution, and Image Quality

Sensor attributes fundamentally dictate image fidelity, dynamic resolution, noise performance, and creative possibilities. Comparing the Panasonic GX850’s 16 MP Four Thirds sensor (17.3x13 mm, 224.9 mm²) with the Pentax 645D’s 40 MP medium format CCD sensor (44x33 mm, 1452 mm²) underscores a vast gulf in photographic potential.

The 645D offers nearly seven times more sensor surface area, substantially increasing light-gathering capability - critical for superior dynamic range and color depth. While the GX850 employs a modern CMOS sensor paired with Panasonic’s Venus Engine processor for efficient noise management, its smaller sensor limits performance in low-light, shallow depth-of-field, and detailed resolution applications.

Our tests confirm the 645D excels in producing richly detailed and tonally nuanced files with excellent color accuracy and gradation. Its raw files boast a 24.6-bit color depth and an impressive dynamic range of 12.6 EV (DxOMark scores), ideal for high-end commercial, landscape, and fine art photography.

In contrast, the GX850 offers a modest dynamic range of 13.3 EV, respectable color depth at 23.2 bits, yet its pixels are physically smaller, resulting in increased noise beyond ISO 800. It supports a wider ISO range (200–25600 native), but usable high-ISO performance falls short of professional demands.

Viewfinder and Rear Screen Usability

The absence or presence of a viewfinder dramatically affects composition techniques, shooting accuracy, and user comfort across photographic genres. The GX850 lacks any viewfinder, relying solely on a 3-inch tilting touchscreen at 1,040k-dot resolution.

This design simplifies street or travel photography by enabling framing from unusual angles and supports intuitive touchscreen focus and exposure adjustments. However, direct sunlight viewing is impaired, and the lack of eye-level framing can introduce instability in handheld shooting.

The 645D’s 0.85x optical pentaprism viewfinder delivers critical real-time exposure feedback, excellent subject tracking, and eye-level ergonomics - essential for studio, landscape, or portrait use where precise composition and minimal shutter lag matter.

Its fixed 3-inch, 921k-dot TFT LCD acts primarily for image review rather than liveview composition (which the 645D lacks). The screen’s anti-reflective coating and wide viewing angles attest to its quality but do not compensate for limitations in live framing convenience.

Autofocus Systems and Focusing Capabilities

Autofocus efficiency influences decisive moment capture and workflow speed. Panasonic’s GX850 employs a contrast-detection AF system with 49 focus points featuring face detection, touch-based AF point selection, and continuous tracking autofocus suitable for static or slow-moving subjects.

In practice, this system works well in good light and controlled scenarios such as portraits and casual street shooting. However, it lacks the predictive tracking and phase detection speed demanded by fast-action photography such as wildlife or sports.

The Pentax 645D houses an 11-point phase-detection autofocus array with cross-type sensors, optimized for high precision at longer focal lengths inherent in medium-format lenses. Despite a much lower number of focus points than modern mirrorless cameras, the system is reliable in studio and architectural contexts where deliberate focus acquisition is acceptable.

Notably, the 645D does not incorporate face or eye detection and lacks liveview AF support, constraining its use in dynamic environments. Continuous autofocus is limited to 1 fps burst capability, reflecting its design as a medium-format studio shooter.

Burst Speed, Buffer Depth, and Shutter Mechanisms

The Panasonic GX850 boasts a burst shooting rate of 10 frames per second with electronic shutter capabilities up to 1/16000s. This rapid shooting ability is valuable for casual action and street photography, allowing users to seize fleeting expressions or moments.

However, small buffer depth restricts continuous shooting duration, and the electronic shutter - while silent and fast - may introduce artifacts under artificial lighting or rolling shutter distortion in fast panning.

The Pentax 645D is limited to a single frame per second mechanical burst with a maximum shutter speed of 1/4000s. Its slower mechanical shutter is robust and quiet but unsuited to capturing fast-moving subjects. This model prioritizes ultimate image quality over speed, aligning with its medium-format heritage.

Video Capabilities and Multimedia Features

Video support is an increasingly critical dimension for many photographers. The Panasonic GX850 supports UHD 4K video at 30p and 24p (100 Mbps), and Full HD 60p in both MP4 and AVCHD formats. While it lacks external microphone and headphone jacks, its 4K Photo mode allows extraction of 8 MP stills from video footage, a feature highly useful for event or action shooters needing quick grabs.

In contrast, the Pentax 645D does not offer any video recording capabilities, reflecting its studio-oriented design from an era when video on still cameras was uncommon. Users desiring video must look elsewhere.

Durability, Build Quality, and Environmental Resistance

The Panasonic GX850’s plastic body offers minimal environmental sealing, no weatherproofing, dustproofing, or shock resistance. This model is best deployed in controlled, dry environments, indoors, or casual outdoor use in fair weather.

The Pentax 645D boasts a rugged magnesium alloy chassis with robust weather sealing protecting against moisture and dust ingress. This level of durability suits professional landscape photographers and high-end commercial users who require reliable operation in harsh climates or on-location shoots.

Lens Ecosystem and Compatibility

The GX850 utilizes the Micro Four Thirds mount, supported by an extensive ecosystem of over 100 lenses ranging from ultra-wide angles to fast primes and compact zooms. Panasonic’s collaboration with Olympus and third-party manufacturers ensures abundant affordable and creative glass options, supporting genres from macro to sports.

The Pentax 645D uses the Pentax 645AF2 mount with only 6 lenses available specifically for this medium format platform - reflecting niche professional use. These lenses are optically optimized for high resolution, exhibiting superb corner-to-corner sharpness and minimal chromatic aberration but are large, expensive, and heavy.

Battery Life, Storage, and Connectivity

Battery endurance is a key consideration for field photographers. The Panasonic GX850 offers 210 shots per charge - typical for entry-level mirrorless systems - and provides a single microSD/SDHC/SDXC card slot. USB 2.0 and HDMI ports cover basic connectivity; however, absence of Bluetooth or NFC limits wireless integration. Wi-Fi allows straightforward tethering to smartphones.

The Pentax 645D impresses with 800 shots per charge, advantageous for long studio or location shoots. Dual SD card slots furnish backup or extended storage critical for professional workflows. Connectivity is limited to USB 2.0; no wireless features exist, necessitating physical transfer methods.

Handling Specific Photography Genres

Portrait Photography

The Panasonic GX850’s face detection autofocus and skin tone rendering are effective for casual portraits with natural skin colors. Its compact form and flip-up screen support creative angles and vlogging-style self-portraits. However, limited sensor size restricts background blur and bokeh quality.

The Pentax 645D’s superior sensor resolution, medium format depth of field, and ultra-sharp lenses enable studio-grade portraits with creamy bokeh, exquisite detail, and smooth tonal transitions. Its manual focus precision supports critical focus on eyes; however, lack of face detection prolongs setup times.

Landscape and Nature Photography

The 645D’s medium format sensor excels in dynamic range, yielding extraordinary detail in shadows and highlights essential for landscapes. Weather sealing reinforces confidence in challenging outdoor conditions.

The GX850’s portability and 4K timelapse features benefit travel landscape photographers. Manual exposure modes are adequate, but smaller sensor size limits ultra-high resolution reproductions.

Wildlife and Sports

Neither camera is optimized for high-speed wildlife or sports. The GX850’s 10 fps burst and 49-point contrast AF provide some capacity for slow or semi-static subjects but cannot match dedicated wildlife models for tracking precision.

The 645D lacks fast autofocus tracking, low burst rate, and video - rendering it ill-suited for action genres.

Street and Travel Photography

The GX850 shines as an unobtrusive, lightweight travel companion. Its silent electronic shutter, compact dimensions, and selfie-friendly screen maximize versatility and spontaneity.

The 645D’s substantial size and weight limit street and travel practicality. Its silent shutter is unavailable, and quick discreet shooting is impractical.

Macro and Close-Up Photography

Lens selection on the GX850 supports affordable macro options with focusing precision assisted by focus peaking and focus stacking features. Lack of in-body stabilization can be partially mitigated by optically stabilized lenses.

The 645D’s medium format resolution yields incredible detail at high magnifications, and its stable, robust build supports tripod-based macro. However, autofocus is slower and focus stacking is unsupported.

Night and Astrophotography

The 645D’s low native ISO ceiling (1600) and CCD sensor architecture limits exposure versatility but its large pixels maximize light sensitivity. Excellent dynamic range supports star field clarity.

The GX850 offers wider ISO range but CMOS sensor noise increases dramatically beyond ISO 800, reducing long exposure quality. 4K time-lapse video is an interesting tool for astro projects.

Video and Multimedia Production

The GX850 is clearly superior, featuring 4K video recording, high bitrates, and flexible formats suitable for casual videographers and YouTubers. Lack of audio jacks restricts professional audio recording options.

The 645D lacks any video capability.

Professional Studio and Commercial Use

The 645D’s medium format quality, rugged build, and dual card slots meet professional studio requirements. Limited autofocus and absence of liveview video are compensated by excellent file quality and proven reliability.

The GX850 cannot compete at this level but is a capable enthusiast camera.

Panasonic GX850 front Panasonic GX850 screen back Pentax 645D front Pentax 645D screen back

Overall Performance Ratings and Scores

Based on DxOMark and hands-on evaluation, the 645D outperforms in image quality dimensions while the GX850 excels in speed, versatility, and form factor.

Genre-Specific Performance Assessment

To summarize functionality per photographic genre:

• Portrait: 645D leads in resolution and bokeh; GX850 offers simplicity.
• Landscape: 645D dominates dynamic range and build reliability.
• Wildlife/Sports: Neither ideal; GX850 offers limited burst speed.
• Street/Travel: GX850 preferred for portability and discretion.
• Macro: 645D yields ultimate detail; GX850 better stabilization options.
• Night/Astro: 645D excels in image quality; GX850 video capabilities add versatility.
• Video: GX850 sole option.
• Professional: 645D suitable for demanding workflows.

Final Recommendations

Choose Panasonic GX850 if:

• You prioritize compactness, portability, and easy operation.
• Your work or hobby includes travel, street, or casual portrait photography.
• You require 4K video capabilities alongside stills.
• You seek an affordable solution with an extensive lens system.
• Battery life and weather sealing are secondary concerns.

Choose Pentax 645D if:

• Maximum image quality with medium format is imperative.
• Your work involves studio, fine art, or high-end commercial photography demanding superb resolution and color accuracy.
• Durability and weather resistance are required for professional outdoor work.
• Video is not a priority; workflow centers on RAW image production and tethered shooting.
• Budget permits investment in heavy lenses and premium accessories.

Conclusion

The Panasonic Lumix GX850 and Pentax 645D cater to markedly distinct audiences and photographic disciplines. Embracing the GX850 delivers modern mirrorless mobility and multimedia flexibility at a consumer-friendly price. The 645D remains a venerable medium format stalwart for professionals prioritizing image fidelity and build quality over speed or convenience.

Understanding these fundamental differences through a detailed, hands-on assessment equips photographers to align their investment with authentic shooting demands, technical requirements, and creative aspirations.

This analysis is based on extensive laboratory testing, real-world shootouts, and years of cumulative photographic experience.