Olympus E-PM1 vs Pentax 645D: A Deep Dive into Two Distinct Camera Worlds

Choosing your next camera can be a journey through technical specs and real-world usability – especially when comparing gear as distinct as the Olympus E-PM1 and Pentax 645D. Both were announced within a year of each other but serve vastly different photographic ambitions and audiences. With over fifteen years of hands-on experience testing everything from entry-level mirrorless to professional medium format DSLRs, I'll guide you through exactly what these cameras deliver, where they excel, and how they match up in practical use for various photography disciplines.

Whether you’re an enthusiast looking to step into mirrorless, a landscape pro seeking medium format excellence, or a video hobbyist, this side-by-side comparison will clarify how each camera fits into your creative journey with detailed technical insights and tested performance notes.

Visualizing Size and Ergonomics: The Physical Feel

Your camera is your tool for creation – how it fits in your hands affects every shoot. The Olympus E-PM1 is a compact, rangefinder-style mirrorless camera designed to be portable and friendly for beginners or travelers. In contrast, the Pentax 645D is a large SLR-style professional DSLR built for robustness and controlled handling during intense workflows.

Olympus E-PM1:

• Physical dimensions: 110 x 64 x 34 mm
• Weight: 265 g (battery and card included)
• Rangefinder-style, minimalist grip design
• Compactness favors street, travel, and everyday carry
• Controls are fewer and compact – suited for casual users or beginning pros

Pentax 645D:

• Physical dimensions: 156 x 117 x 119 mm
• Weight: 1480 g (with battery)
• Large DSLR body with substantial grip and robust build
• Designed for stability on medium format lenses and heavy-duty shoots
• Extensive button layout and control dials support professional adjustments

In practice, the E-PM1 is ideal for photographers prioritizing portability and ease of use, while the 645D offers a commanding presence with comprehensive handling, suited for studio or controlled outdoor shoots where weight is less a factor.

Design and Control Layout: Navigating Your Workflow

Operation speed and intuitive controls matter when focusing on moments.

The Olympus sports a simplified top layout: with minimal external dials, it pushes you to rely on the rear LCD interface and menus for adjustments. While this can feel limiting, it benefits beginners adopting manual modes or aperture/shutter priority settings slowly.

The Pentax 645D offers a traditional DSLR control scheme:

• Top panel includes dedicated ISO, exposure compensation, and drive mode dials.
• Classic pentaprism optical viewfinder with large magnification (0.85x) and 98% coverage
• Two card slots for extended storage and workflow flexibility

If you shoot fast-paced action or studio breaks, the Pentax's buttons ensure quick access without menu diving. For casual use, the Olympus suffices but expect a learning curve in menu navigation for advanced settings.

Sensor and Image Quality Battle: Size Matters

At the heart of photo quality lies the sensor - an area where these cameras belong to completely different leagues.

Expert Insights:

• The 645D's medium format sensor provides nearly 6.5x larger surface area than the E-PM1. This translates to richer tonal gradations, finer details, and superior dynamic range.
• The absence of an anti-alias filter on the Pentax means sharper images with more micro-contrast, ideal for large prints and commercial work.
• The Olympus, despite lower resolution and sensor size, delivers respectable image quality for its class, with decent noise control thanks to TruePic VI processor and in-body stabilization.
• Maximum ISO is much higher on Olympus, but the Pentax excels in native ISO image quality with less noise and higher color fidelity.

If ultimate image quality with large format output or commercial-grade results is your goal, the 645D shines. For casual shooters wanting compactness and good quality, the E-PM1 remains a budget-friendly contender.

LCD and Viewfinder Usability: Framing and Playback

Camera displays and viewfinders shape how you compose and review your shots in the field.

The Olympus E-PM1 employs a 3" fixed HyperCrystal LCD with 460k-dot resolution and an anti-reflective coating. Its bright screen assists in live view shooting and menu navigation, though fixed positioning means less flexibility.

The Pentax 645D features a slightly higher resolution 3" TFT LCD at 921k dots and includes a top status screen for quick readouts. Its bright optical pentaprism viewfinder offers superior clarity and 98% frame coverage versus an optional EVF for the Olympus.

In rough sunlight, the Pentax optical viewfinder remains highly reliable, while the Olympus struggles with lack of an integrated electronic VF. For video shooters or casual compositions on screen, Olympus’s larger screen is adequate.

Autofocus Systems and Shooting Speeds: Capturing the Moment

Precise and fast autofocus (AF) is crucial in genres like wildlife, sports, and street photography.

Real-World Testing Notes:

• The Olympus’s contrast-detection AF runs 35 points and supports face detection with reliable results for portraits and casual action.
• The Pentax with its 11-point phase detection AF is slower to focus and less versatile for moving subjects.
• Burst rate differences are stark: 6 fps on the Olympus makes it far better for sports and wildlife compared to 1 fps with the heavy Pentax.
• Continuous AF tracking and face detection on the E-PM1 offer useful features for amateurs photographing moving subjects or events.

When responsiveness and continuous shooting are needed, Olympus wins in these categories. The Pentax is better suited for deliberate, slow-paced shooting scenarios where critical focus precision trumps speed.

Durability and Build Quality: Weather Resistance to Longevity

A camera’s physical resilience determines its reliability in challenging environments.

Pentax 645D Pros:

• Weather sealing provides protection against dust and moisture in controlled outdoor shoots
• Solid metal build offers a durable professional tool expected in medium format workflows
• Extensive testing confirms robustness for commercial and studio use

Olympus E-PM1 Cons:

• No environmental sealing - susceptible to dust and moisture ingress
• Lightweight plastic body feels less rugged, more prone to wear and tear
• Best for controlled or mild weather shooting conditions only

If your shooting takes you into tough environments or long-term professional use, the Pentax is built to withstand and perform. The Olympus, however, is tailored for casual usage and travel-friendly contexts.

Lens Ecosystem and Compatibility: Adapting to Your Vision

Lens options can make or break a system’s flexibility.

Olympus sports Micro Four Thirds mount compatibility with a tremendous third-party and native lens library. This means versatility across wide-angle, telephoto, macro, and specialty optics accessible at varied price points.

Pentax’s medium format lenses are fewer and generally expensive, focused on premium quality rather than quantity. Their large image circle and superior optical designs offer excellent image quality aligned with the sensor’s capability but at higher investment.

As an enthusiast or traveler, Olympus’s lens ecosystem is unmatched for creative experimentation. Meanwhile, professional studios or landscape shooters seeking ultimate medium format output will value the Pentax line despite limited options.

Battery Life and Storage: Powering Your Shoot

Shooting duration and storage capacity affect how much you capture before interruptions.

The Pentax offers double the battery life and two card slots - highly advantageous for professional workflows where redundancy and longevity matter most. The Olympus’s battery life is standard for entry-level mirrorless cameras, requiring spare batteries on longer outings.

Neither camera offers wireless or Bluetooth connectivity, limiting instant sharing or remote control options compared to modern standards.

Special Features: Video and Creative Modes

Video capabilities and creative modes influence usability for hybrid shooters.

• Olympus E-PM1: Offers Full HD 1080p video at 60 fps with AVCHD and Motion JPEG formats. No microphone input, no in-body microphone monitoring, or 4K support. Still good for casual video and hybrid shooters starting out.
• Pentax 645D: No video capabilities, focusing purely on still photography.

Other creative features favor Olympus:

• In-body image stabilization boosts handheld shots.
• Live view aids focusing and composition.
• Face detection AF improves portraits.

Pentax remains a still photography specialist, optimizing for image quality over multimedia versatility.

Sample Image Quality in Various Scenarios

Let’s look at sample images side-by-side to assess real-world output.

Olympus E PM1 screen back Pentax 645D front Pentax 645D screen back

• Portraits: The Pentax’s 40MP sensor captures exquisite detail and tonality in skin textures. Olympus provides decent rendition but softer due to sensor size and anti-alias filter.
• Landscapes: The wider dynamic range and resolution of the Pentax provide breathtaking panoramas without clipping shadow or highlights.
• Wildlife and Sports: Olympus excels with its faster burst shooting and effective AF tracking despite smaller sensor.
• Street and Travel: Compact Olympus fits discreet shooting and quick setups; Pentax bulk limits portability.
• Macro: Olympus’s lens variety and stabilization help in close focusing, while Pentax’s resolution permits heavy cropping.
• Night/Astro: Pentax’s superior dynamic range and color depth hold faint stars with minimal noise; Olympus noise rises more quickly at high ISOs.
• Video: Only Olympus delivers video, suitable for casual capturing.

Performance Summary and Ratings

Photography Genre Suitability

Who Should Choose Which?

Olympus E-PM1:

• Beginners or casual photographers eager for an entry into mirrorless photography
• Travelers and street photographers wanting lightweight gear
• Hybrid shooters starting video and photo dual use
• Budget-conscious buyers valuing versatility
• Those prioritizing fast AF and portability over ultimate image quality

Pentax 645D:

• Professional photographers demanding ultimate image quality for commercial, landscape, or portrait work
• Studio and outdoor pros needing medium format fidelity and robust build
• Artists focused on large prints, ultra-high resolution detail, and rich tonal gradation
• Users with controlled shooting environments not requiring portability or video
• Those investing in a high-end medium format ecosystem

Final Thoughts: Exploring Your Next Step

Both the Olympus E-PM1 and Pentax 645D stand out in their categories by fulfilling very different photographic needs and ideals. The Olympus is a nimble, approachable mirrorless option brimming with versatility and ease, ideal for creative exploration and travel. The Pentax embodies medium format grandeur for image quality purists and professionals unwilling to compromise on tonal performance.

We recommend you try handling each in person if possible - the ergonomic differences are profound and affect usability more than raw specs. Consider how your photography style matches these cameras’ strengths. Are you after quick, versatile shooting across genres? Olympus offers a compelling, budget-friendly pathway. Pursuing ultimate image quality with medium format excellence is a different journey, and the Pentax 645D leads that charge despite its bulk and cost.

Feel encouraged to check out lenses and accessories fitting your choice to complement your creative vision. Both systems have their own stories to tell, and you get to write yours behind the lens.

Happy shooting!