Olympus E-M5 III vs. Pentax K-70: An In-Depth Comparison for Discerning Photographers

Selecting a camera that harmonizes with your photographic ambitions, skill level, and shooting style requires a meticulous look beyond headline specifications. The Olympus OM-D E-M5 III and the Pentax K-70, while both targeting enthusiast-level photographers, embody distinctly different design philosophies and technological heritages. This comprehensive comparison draws from extensive hands-on testing across diverse genres, technical bench assessments, and real-world usability evaluations to help clarify which model aligns with your creative and operational needs.

Form Factor and Handling: Mirrorless Sophistication Versus DSLR Solidity

Olympus E-M5 III pursues a compact, lightweight mirrorless format with a body weighing just 414 grams and dimensions of 125 x 85 x 50 mm. The camera’s SLR-style mirrorless body is designed for portability without sacrificing control, boasting an intuitive grip and well-thought-out button placement for frequent settings access. Its articulating touch-enabled 3-inch LCD with 1,040k dots enhances live view framing flexibility and touch interactions, ideal for video and challenging angles.

Conversely, the Pentax K-70 adheres to a more traditional entry-level DSLR form factor, markedly bulkier and heavier at 688 grams and 126 x 93 x 74 mm. Its build conveys ruggedness and familiarity for DSLR users, with a larger grip and more tactile buttons but lacking touchscreen functionality. Although heavier, the K-70 integrates full weather sealing, proving advantageous in adverse conditions.

The physical disparity implies that photographers prioritizing travel, street, or casual shooting may find the E-M5 III’s portability and touchscreen highly beneficial. In contrast, the K-70’s heft and robust DSLR ergonomics favor those who regularly shoot outdoors and value a solid interface over compactness.

Control Layout and Customizability

Both cameras offer manual controls including shutter priority, aperture priority, and manual exposure modes. The Olympus’s electronic viewfinder (EVF) with 2,360k-dot resolution delivers a close-to-final preview with exposure and color accuracy feedback, enhancing precise framing and critical focus accuracy. The Pentax employs a traditional optical pentaprism viewfinder, providing zero lag and natural viewing but without exposure feedback, which could hinder beginner users learning exposure adjustments on the fly.

The E-M5 III supports 121 autofocus points with contrast and phase detection hybrid AF, yielding faster and more versatile autofocus across various points in the frame. The K-70 provides 11 autofocus points (9 cross-type), relying solely on phase detection AF, a configuration that, while reliable, does not deliver the same precision or coverage breadth.

The Olympus also supports fully articulating touchscreen operation, allowing touch-to-focus and touch-shutter - a workflow advantage unattainable in the Pentax’s non-touch interface.

Sensor Technology and Image Quality Considerations

Sensor Formats and Resolution:

The Olympus E-M5 III utilizes a Four Thirds 17.4 x 13 mm MOS sensor with a 20.4-megapixel resolution, integrated with a TruePic VIII processor. The micro four-thirds sensor area measures 226 mm² and employs a native ISO range of 200-25,600 (expandable to 64 ISO). Notably, it incorporates an anti-aliasing filter to minimize moiré at the cost of some fine detail resolution.

Pentax K-70 sports an APS-C 23.5 x 15.6 mm CMOS sensor, offering a larger sensor area of 367 mm² and higher resolution at 24 megapixels. Significantly, it eschews an anti-aliasing (AA) filter to maximize sharpness, enabling more capture of fine texture detail - albeit with potential moiré artifacts in dense patterns.

Image Quality Impact:

From testing under controlled studio and field conditions, the K-70’s larger sensor provides superior dynamic range and better noise handling at moderate to high ISOs. Pentax’s ability to push ISO up to 102,400 (albeit with extreme noise) enables more flexibility in low-light scenarios. Olympus’s maximum 25,600 ISO ceiling, combined with smaller sensor dimensions, results in a noise floor that becomes noticeable beyond ISO 6400, especially in shadow retention when compared to the APS-C alternative.

However, Olympus’s 5-axis in-body image stabilization contributes significantly during handheld shooting, allowing longer exposure times without blur - a compelling advantage in low light or macro scenarios. This means the smaller sensor’s inherent limitations in noise can be somewhat mitigated by stabilization-enabled longer exposures.

Both cameras shoot RAW, enabling advanced post-processing with more latitude, but the K-70’s larger pixel pitch and omission of an AA filter make it the preferable choice for photographers placing utmost priority on ultimate detail retention and dynamic range.

Display and Viewfinder: User Interface and Compositional Aids

The Olympus’s 3-inch 1,040k-dot fully articulating touchscreen enhances usability, especially in video and unconventional shooting stances, such as overhead or low to the ground. Touch-to-focus and intuitive menu navigation reduce fumbling, which becomes apparent during extended handheld sessions or videography.

The Pentax provides a similar 3-inch screen but with 921k-dot resolution and no touch functionality. Its articulating mechanism is robust but slower to access when rapid repositioning is needed. The optical viewfinder excels for photographers favoring traditional shooting styles and those who rely heavily on optical feedback without lag or digital artifacts.

Photographers invested in hybrid shooting - stills plus video - will appreciate the E-M5 III’s interface, as touchscreen responsiveness drastically improves workflow speed and framing accuracy.

Autofocus and Burst Shooting Performance

The Olympus E-M5 III’s autofocus system is one of its strongest assets. Featuring 121 focus points, it combines contrast and phase detection AF to deliver swift subject acquisition, with continuous autofocus tracking capabilities suitable for dynamic subjects. Face detection is effective, particularly for portraiture, but lacks dedicated animal eye autofocus present in newer models.

Continuous burst shooting at up to 30 fps (electronic shutter) or sustained 10 fps with mechanical shutter provides considerable advantage for capturing wildlife and sports action.

Comparatively, the Pentax K-70’s 11 autofocus points, while cross-type, are more limited and correspondingly slower in acquisition and tracking speeds. Burst shooting peaks at ~6 fps, acceptable for entry-level sports photography but falling short for professionals seeking high frame-rate sequences.

Thus, Olympus is better poised for fast-paced scenarios such as wildlife, action, and sports, while Pentax best serves moderately paced shooting environments.

Olympus E M5 III front Olympus E M5 III screen back Pentax K 70 front Pentax K 70 screen back

Practical Imaging Tests Across Genres

Portraiture:
Olympus’s effective face detection and ability to combine high-res EVF framing facilitate precise focusing on eyes and subtle facial features. The micro four-thirds sensor delivers good depth of field control aided by the crop factor but lacks the natural bokeh smoothness and subject-background separation achievable with the Pentax’s APS-C sensor paired with fast prime lenses. The K-70’s larger sensor offers creamier defocus and more lifelike skin tones, although Olympus achieves respectable color fidelity.

Landscape:
Pentax’s superior resolution and dynamic range provide an edge in landscape, where fine detail and wide tonal gradations across shadows and highlights are paramount. Olympus’s in-body image stabilization assists in handheld shooting at slow shutter speeds beneficial for hand-held twilight and long exposure landscapes, offsetting some sensor size disadvantages.

Wildlife and Sports:
Olympus’s faster autofocus with a denser AF point array and 30 fps burst rate outperform Pentax’s more modest AF and 6 fps speed, making it the better candidate for wildlife and sports requiring rapid subject tracking.

Street Photography:
The E-M5 III’s compact, lightweight mirrorless body offers discretion and quieter operation thanks to the electronic shutter option - valuable in candid scenarios. Pentax is bulkier and more conspicuous but benefits from an optical viewfinder that many street shooters find more natural for seeing through the lens.

Macro:
Olympus’s 5-axis stabilization and high shutter speed ceiling encourage sharp close-ups without a tripod. The smaller sensor’s greater depth of field inherently eases focus stacking and bracketing; however, Pentax’s superior sensor resolution and dynamic range yield images with cleaner detail rendition when using macro lenses.

Night and Astro Photography:
Pentax’s wider ISO range and generally lower noise performance under extreme low-light conditions are advantageous here, although Olympus’s stabilization enables longer exposures handheld. Olympus lacks native dedicated astro modes but includes time-lapse functionality shared with Pentax.

Video:
Olympus shoots 4K UHD at 24p with MOV H.264 compression and supports external microphones, making it more suited to casual videographers and hybrid shooters. The Pentax is limited to Full HD 1080p up to 60i, and lacks 4K capabilities. Neither camera features headphone jacks for audio monitoring, restricting professional audio control.

Build, Durability, and Weather Sealing

Both cameras offer environmental sealing appropriate for enthusiast use but neither is fully waterproof, shockproof, or freeze-proof. The Pentax K-70 features a well-executed weather sealing design, sealing over 70 points, including the memory card and battery door, rated to resist dust and moisture in challenging conditions. Olympus’s E-M5 III also carries comprehensive sealing but benefits from its smaller body which may limit exposure risk during strenuous outdoor use.

Lens Ecosystem and Mount Compatibility

Olympus employs the Micro Four Thirds (MFT) mount, granting access to a substantial complement of over 100 lenses from Olympus, Panasonic, and third parties. This range includes ultra-compact primes, versatile zooms, specialized macro and fisheye lenses, which coupled with the camera’s sensor multiplier of 2.1x extends effective reach greatly for telephoto and wildlife applications.

Pentax K-70’s Pentax KAF2 mount supports a large legacy of over 150 lenses, encompassing decades of high-quality optics, from affordable primes to pro-class HD lenses. The full-frame compatible K-mount lenses provide excellent versatility, but with a crop factor of 1.5x, telephoto reach is somewhat less extended than the MFT system.

For photographers invested in a wide range of lenses or those integrating legacy optics, Pentax presents compelling value; however, modern autofocus and optical image stabilization in Olympus lenses may outperform older Pentax lenses lacking such features.

Battery Life and Storage Convenience

Pentax’s DSLR design confers a battery life advantage of approximately 410 shots per charge, compared to Olympus’s 310 shots. This is typical for mirrorless cameras, which consume more power due to electronic viewfinders and sensor-based stabilization.

Both cameras support SD cards; Olympus supports faster UHS-II cards offering improved write speeds and buffering for high frame rate shooting, while Pentax is compatible with UHS-I cards only. The single card slot design in both cameras may be a bottleneck for professional workflows requiring redundant backups.

Connectivity, Wireless Features, and Workflow Integration

Olympus benefits from built-in Wi-Fi and Bluetooth for remote control and image transfer to mobile devices with relative ease, enhancing tethered shooting and social media sharing workflows. Pentax has built-in Wi-Fi but lacks Bluetooth integration, potentially requiring a separate GPS module for geotagging.

USB 2.0 ports on both cameras limit tethering speed; thus, professionals requiring fast data offload may find these interfaces a constraint.

Price-to-Performance Analysis and Final Recommendations

At current retail pricing, the Olympus E-M5 III carries a substantial $1,199 price tag reflecting its advanced sensor stabilization, hybrid AF system, 4K video capability, and compact mirrorless build. The Pentax K-70, priced around $649, positions itself as a budget-friendly DSLR with a superior larger sensor, robust weather sealing, and a substantial lens ecosystem at a more accessible cost.

Who Should Buy the Olympus E-M5 III?

• Photographers prioritizing portability and silent operation - street, travel, and hybrid still/video shooters.
• Wildlife and sports photographers requiring fast, accurate autofocus and high frames per second.
• Users invested in Micro Four Thirds lenses desiring an advanced stabilization system.
• Videographers seeking 4K video with external mic support and articulating touchscreen control.

Caveats: Smaller sensor limits dynamic range and high ISO performance relative to APS-C. Battery life is modest.

Who Should Consider the Pentax K-70?

• Landscape, portrait, and night photographers who benefit from a larger APS-C sensor and superior dynamic range.
• Enthusiasts desiring rugged, weather-sealed DSLR handling with access to extensive K-mount lenses.
• Budget-conscious buyers seeking 24MP detail at a significantly lower cost.
• Photographers resistant to touchscreen or mirrorless system adaptations who prefer an optical viewfinder.

Trade-offs: Slower AF, lower burst rates, no 4K video, and heavier body reduce suitability for rapid action or hybrid shooting.

Summative Perspective

Both cameras exemplify distinct niches within the market. The Olympus E-M5 III epitomizes the matured mirrorless segment’s strengths - speed, stabilization, compactness, and video finesse - well suited for dynamic genres and modern workflows. The Pentax K-70 doubles down on proven DSLR robustness, larger sensor advantages, and optical viewfinder experience appealing to photographers favoring traditional design with serious image quality on a leaner budget.

Selecting between these two models hinges on your priority spectrum - whether it leans towards agility and hybrid features or sensor size and optical heritage.

Appendix: Technical Profile Summary

This balanced, in-depth comparison aims to empower both enthusiasts and professionals with nuanced insights derived from rigorous hands-on experience and technical scrutiny. Your ultimate choice should be aligned with your shooting subject preferences, operational workflows, and ecosystem investments.