Olympus E-M5 III vs Pentax K-3 II: The Battle of Advanced Classics for the Discerning Photographer

When seasoned photographers ask me for advice on the Olympus OM-D E-M5 III and the Pentax K-3 II - two stalwarts from different generations and sensor philosophies - I always dig beyond the spec sheets. Both cameras reshape the meaning of advanced in their own ways: Olympus’s E-M5 III (2019) is a feature-packed mirrorless marvel with Micro Four Thirds heritage, while Pentax’s K-3 II (2015) represents an ergonomic, rugged APS-C DSLR that lasts longer than some friendships.

Having extensively tested both in the field across disciplines - portraits to wildlife, landscapes to astro - I’m here to guide you through an honest, practical comparison and help you decide which deserves that coveted spot in your kit. Buckle up for a nuanced ride!

Getting a Feel for It: Size, Weight, and Ergonomics

Before diving into sensor sizes and pixels, the first impression always boils down to how a camera feels in hand. Let’s start by sizing up these two contenders.

The Olympus E-M5 III is surprisingly compact and lightweight for an advanced camera at just 414 grams and dimensions around 125 x 85 x 50 mm. Its Micro Four Thirds design philosophy embraces portability without sacrificing substantial control or lens ecosystem - quite a feat.

Compare that to the Pentax K-3 II’s much larger, robust DSLR body: at 800 grams and a chunkier 131 x 100 x 77 mm, it’s a mid-size SLR that demands respect (and a strong routine to carry it around all day).

The E-M5 III’s grip is snug and serviceable for long shoots, though if you have larger hands, the relatively smaller chassis may feel a bit less substantial. Pentax’s deep grip, classic SLR heft, and fully articulated controls evoke an analog camera vibe that many maestros swear by for extended sessions - especially in tough conditions.

Both cameras have weather sealing, but the Pentax’s build quality feels thicker, sturdier, even ready to battle the elements like a tank - if you’re into serious landscape or wildlife photography in unforgiving terrain, that extra protection might be a decisive factor.

Design and Control Layout: The Photographer’s Command Center

Ergonomics aren’t just about size - button placement and control logic are pivotal for quick adjustments under fire.

The Olympus E-M5 III brings a modern twist to the SLR-style mirrorless body: fully articulating 3-inch touchscreen LCD at 1040k dots, lush electronic viewfinder (EVF) with 2.36M-dot resolution, and an intuitive menu system. Touch-to-focus and customizable dials feel responsive, making it a joy for photographers who value quick, precise adjustments with minimal fuss.

Pentax K-3 II’s design is a throwback but with home-grown expertise - all physical buttons, no touchscreen, and a conventional 3.2-inch fixed LCD. The top-plate LCD offers quick readouts - handy for those who prefer no-nonsense analog-style shooting. The optical viewfinder is bright, crisp, and covers 100% of the frame, albeit lacking eye-detection autofocus integration found on modern mirrorless.

For usability, it boils down to preference: if you love tactile controls and optical viewfinder authenticity, Pentax’s layout rings true. Want more features at your fingertips with touch support? Olympus steers that win.

The Heart of the Image: Sensor Size, Resolution & Image Quality

Now let’s talk about the all-important sensor battle - the core of imaging performance.

The Pentax K-3 II sports a 24-megapixel APS-C CMOS sensor (23.5 x 15.6 mm), lacking an anti-aliasing filter for razor-sharp images. APS-C remains the DSLR standard, balancing high resolution and good noise control, with better native ISO headroom up to 51200.

On the flip side, Olympus’s E-M5 III houses a 20-megapixel Four Thirds sensor (17.4 x 13 mm) with a native ISO range topped at 25600 (with extended ISO 64 at the low end). The smaller sensor footprint means a 2.1x crop factor and naturally less light-gathering capability compared to APS-C but benefits from in-body 5-axis sensor stabilization to compensate.

How do these specs translate in real-world image quality? Despite the smaller sensor, Olympus’s processor - a TruePic VIII - efficiently extracts detail with commendable noise handling up to ISO 6400, making it perfect for outdoors and daylight work. Pentax, with its larger sensor and no AA filter, delivers sharper images with superior dynamic range and color depth (DxO’s rated 23.6 bits color depth, 13.6 stops dynamic range), particularly visible in landscape and studio portrait scenarios.

Bottom line: If ultimate resolution and dynamic range are priorities - landscapes, studio portraits - Pentax K-3 II leads the pack. For versatility with stabilization and respectable image quality, particularly in handheld or unstable conditions, Olympus E-M5 III holds strong.

Viewing and Interface: Where the Photographer Sees the World

Taking a peek at how each camera puts its frame in front of your eye:

Olympus’s fully articulated touchscreen stands out for vlogging, macro work from low angles, and shooting tricky compositions - plus it supports touch-to-focus and swipe-customizable menus. The EVF, while smaller than DSLRs, allows 100% coverage with digital overlays like histograms, focus peaking, and live exposure previews.

Meanwhile, the Pentax K-3 II sticks to a fixed 3.2-inch LCD and a traditional optical pentaprism viewfinder - bigger and more natural to the eye, but no digital enhancements (eye detection autofocus aside). Its top plate LCD helps you confirm settings at a glance without peeking rearward.

In short, Olympus’s screen advances usability with live data; Pentax’s optical prowess caters to classic photography purists.

Autofocus Systems: Fast & Furious or Classic Precision?

Autofocus performance often makes or breaks usability, especially in action or wildlife shooting.

Olympus boasts a hybrid autofocus system with 121 contrast and phase detection points, face detection, and eye detection autofocus - catering very well to moving subjects and photographers who want a bit of automation help. Continuous autofocus modes here go up to a blazing 30fps burst rate with tracking using the electronic shutter, fantastic for fleeting moments.

Pentax K-3 II uses a 27-point AF system with 25 cross-type sensors, also with face detection but no eye detection or animal eye AF (Olympus lacks this too). Its continuous shooting cap is modest at 8.3 fps, which is respectable but well behind Olympus’s mirroring mirrorless efficiency.

In practical use, Olympus feels more agile when tracking birds in flight or sports, especially in good light, while Pentax delivers dependable, if slower, focus acquisition better suited for steady, deliberate shooting.

Performance by Photography Genre: Which Makes Your Life Easier?

Let’s visit the studios, the field, the streets, and the wild - to see how each camera performs discipline by discipline.

Portrait Photography

Portrait shooters crave exquisite skin tones, subtle bokeh, and sharp eye focus. Olympus’s capable eye detection and 5-axis stabilization let you shoot handheld in softer light with smooth results. The smaller sensor means less compression of background; portraits have a slightly deeper depth of field for the same aperture.

Pentax’s larger APS-C sensor, combined with no AA filter, offers punchier detail and creamier bokeh with fast lenses, excelling in controlled lighting studios. Its color rendering leans toward natural warmth, flattering skin tone reproduction.

Winner? Pentax edges out for pure image quality and background separation. Olympus wins on autofocus convenience and handheld versatility.

Landscape Photography

Pentax’s edge here is significant - superior dynamic range, higher native resolution, and a weather-sealed body built like a fortress empower stunning wide vistas and detailed shots. Its sensor captures more nuanced tones in shadows and highlights.

Olympus’s smaller sensor means a tradeoff in ultimate detail, but the in-body stabilization helps compensate in tricky tripod-less scenarios or low light. Its articulating screen lets you compose rooftop or ground-level shots easily.

Winner? Pentax’s larger sensor and rugged nature make it the landscape champ.

Wildlife

This is where Olympus’s lightweight and fast shooting burst rate become critical. The 2.1x crop factor essentially extends telephoto reach - often handy when photographing elusive birds or animals. Its 30fps burst with continuous autofocus is a rare luxury here.

Pentax, while offering solid build and APS-C sensor vistas, is slower (8.3 fps) and heavier, making long hikes harder.

Winner? Olympus for speed and reach advantage; Pentax if you prioritize image quality for big prints.

Sports Photography

Speed and tracking accuracy dominate this genre. Olympus’s hybrid AF with face/eye recognition and a blistering 30 fps burst rate is a boon for fast paced sports.

Pentax keeps up respectably but is no match in focus responsiveness or frame rate for action sequences.

Winner? Olympus.

Street Photography

Portability, discrete operation, and quick focus matter here. Olympus’s smaller size, touchscreen operation, and silent shutter mode make it more agile and less obtrusive - a huge bonus for candid street shots.

Pentax’s bulk and shutter noise might draw more attention; its fixed LCD limits shooting angles.

Winner? Olympus.

Macro Photography

The Olympus E-M5 III shines due to its stabilization and articulated screen, aiding precision and comfort at close distances. The 5-axis IS combined with focus bracketing/stacking support opens refined macro work.

Pentax struggles here given no focus bracketing or stacking and fixed rear screen.

Winner? Olympus.

Night and Astro Photography

High ISO performance and long exposures govern night shots. Pentax’s cleaner APS-C sensor with ISO up to 51200 outperforms Olympus in noise control and image quality. Its weather sealing and built-in GPS for star trail logging also add practical value for night shooters.

Olympus’s limited maximum ISO and smaller sensor size mean more noise, but stabilization can help with handheld starscapes of the Milky Way.

Winner? Pentax.

Video Capabilities

Olympus offers 4K UHD (4096 x 2160) at 24p with 237 Mbps bitrate, HDMI out, microphone input but no headphone jack. No eye autofocus in video but decent stabilization for handheld clips.

Pentax tops out at 1080p 60i/30p, with microphone and headphone jacks - good ergonomics but no 4K or advanced video features.

Winner? Olympus’s 4K support makes it more versatile for hybrid shooters.

Travel Photography

Balancing weight, versatility, and battery life is key. Olympus’s lightweight body and excellent image stabilization make it a perfect travel companion for street, landscapes, and portraits in one package.

Pentax gains points for battery life (720 shots vs 310) and dual card slots, but the weight and bulk might slow you down over long treks.

Winner? Olympus for portability; Pentax for endurance and file security.

Professional Use

Pro workflows demand file quality, reliability, and integration with peripherals. Pentax’s APS-C sensor’s RAW files deliver better latitude for editing. Dual storage slots reduce risk.

Olympus offers a modern USB 2.0 interface (not the speediest), built-in wireless (Bluetooth), but only one SD slot and more limited tethering.

Winner? Pentax for pro photographers needing robust backup and editing latitude.

Build Quality, Weather Sealing & Battery Life

Both cameras are weather sealed, but Pentax’s larger, sturdier body inspires confidence on long expeditions. However, Olympus also impresses with a solid magnesium alloy chassis and splash-proof rating despite its compactness.

Battery life highlights a significant difference: Pentax K-3 II’s 720 shot CIPA rating doubles Olympus’s 310 shots. This matters on extended shoots or when traveling off-grid.

Lens Ecosystems: What’s in Your Arsenal?

Olympus’s Micro Four Thirds mount boasts over 100 lenses, including excellent primes and fast zooms from Olympus, Panasonic, and third parties - a massively versatile ecosystem great for everything from macro to super-telephoto (noting the crop factor).

Pentax’s KAF2 mount accesses 151 lenses including legacy glass, modern SDM autofocus lenses, and a slew of weather sealed, rugged optics - a treasure trove for DSLR purists or those invested in Pentax glass.

Connectivity, Storage & Extras

Olympus’s built-in Wi-Fi and Bluetooth allow quick image transfer and camera control - handy for social media-centric travelers.

Pentax requires optional Wi-Fi and offers GPS built-in - prized for geo-tagging landscapes and adventure shots.

Storage is another point: Pentax sports dual SD card slots (UHS-II), Olympus has a single slot - so consider your backup needs.

Let’s Put a Bow on It: Performance Scores and Overall Verdict

A glance at performance ratings shows Olympus shining in autofocus speed and burst rate, video, and portability, while Pentax captures better image quality, battery life, and build durability.

The detailed breakdown confirms Olympus excels at wildlife, sports, street, video, and macro, whereas Pentax dominates landscapes, portraits, night, and professional reliability needs.

Sample Images - Giving You a Visual Taste

Enough talk! Here’s a gallery of sample images side-by-side for you to eyeball the nuances yourself.

Olympus E M5 III front Olympus E M5 III screen back Pentax K 3 II front

Who Should Buy Which Camera?

Choose the Olympus E-M5 III if:

• You want a lightweight, compact system that excels at fast action (sports, wildlife)
• You prioritize in-body stabilization and 4K video
• You appreciate touchscreen controls and modern interface features
• You shoot a lot handheld or need flexible articulation for macro or vlogging
• Portability and fast autofocus count above all

Choose the Pentax K-3 II if:

• You demand superior image quality with high dynamic range and resolution for landscapes or portraits
• You need a rugged DSLR body with long battery life and professional dual card slots
• You desire classic optical viewfinder experience and direct tactile control layout
• You work often in night/astro photography or professional workflows needing the best RAW latitude
• You already own or plan to invest in Pentax’s vast, weather-sealed lens ecosystem

Final Thoughts from the Field

I’ve lugged both these cameras through dawn hikes in Yosemite, intense soccer games, intimate studio setups, and long hours of street wandering in Paris. The Olympus E-M5 III impressed me with its nimble focus, whisper-quiet shutter, and video chops; it felt like a Swiss Army knife, ready for anything without weighing me down.

The Pentax K-3 II, in contrast, felt like a reliable workhorse where image quality and robustness are king - the type of camera you trust to keep shooting no matter what, that rewards patience and deliberate craftsmanship.

Neither camera is “better” universally - they simply serve different philosophies and demands. Choosing one means aligning your priorities: speed and versatility with Olympus, quality and endurance with Pentax.

If you found this detailed tour helpful or have questions about specific uses, drop a comment or reach out. I love geeking out on cameras that inspire us to create - and I hope whichever you pick keeps firing your passion for years to come. Happy shooting!

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Author: A seasoned camera tester with 15+ years examining and shooting with digital cameras across genres - committed to honest, practical reviews you can trust.