Olympus E-M10 IV vs Pentax K-S1: An In-Depth Practical Comparison for Photography Enthusiasts

Choosing a camera is never just about specs on paper or flashy marketing buzzwords. After putting both the Olympus OM-D E-M10 IV and the Pentax K-S1 through their paces in a variety of real-world scenarios, I’m here to share insights that you won’t find just by scrolling through spec sheets. Having shot portraits in golden hour glow, chased falcons in windy conditions, and squeezed these cameras into tight street corners, I want to help you decide which system fits your style, budget, and creative vision.

So grab a coffee (or whatever fuels your shutter finger), and let’s dig into this matchup between Olympus’s compact Micro Four Thirds mirrorless contender and Pentax’s mid-size DSLR classic.

Size, Ergonomics, and Handling: Pocketability vs. Grip

First impressions often hinge on how the camera feels in hand - and right off, the differences here are stark.

The Olympus E-M10 IV boasts a svelte, highly portable SLR-style mirrorless form factor measuring 122×84×49mm and weighing a lighter 383g with battery. It fits snugly in small bags and doesn’t demand a gym membership to tote it around on long travel days. The smaller Four Thirds sensor lets Olympus shave off bulk, appealing immediately to travelers or street shooters who prize discreteness.

Conversely, Pentax’s K-S1 sits as a mid-size DSLR at 121×93×70mm and quite a hefty 558g. It feels robust, with a heft that some find reassuring for stability when shooting wildlife or landscapes. Its deeper grip offers a confident hold, especially when paired with larger Pentax lenses. However, it’s less pocket-friendly and demands a backpack or dedicated camera bag to haul around comfortably.

Olympus packs modernity into its body with a clean control layout, touchscreen interface, and a tilting 3.0-inch LCD. Pentax’s fixed 3.0-inch screen lacks touchscreen but features illuminated buttons - handy when shooting in dim environments or late-night events.

For beginners or those switching from smartphones, Olympus’s touchscreen usability sweetens the deal, allowing intuitive focusing and menu navigation. Pentax puts more emphasis on traditional DSLR controls, preferred by tactile shooters who like physical dials for shutter speed and aperture.

Sensor Technology and Image Quality: Cropped Sensors with Big Impacts

Here’s where gearheads and pixel-peepers start to salivate. Both cameras sport 20MP APS-C or smaller sensors but take very different approaches:

• Olympus E-M10 IV features a Four Thirds CMOS sensor measuring 17.4×13mm (about 226 mm²) with a 2.1x crop factor.
• Pentax K-S1 rocks a larger APS-C CMOS sensor sized 23.5×15.6mm (some 366 mm²) with a 1.5x crop factor.

A bigger sensor often translates to better low-light performance due to larger photosites (pixels), improved dynamic range, and shallower depth of field images - yes, the elusive creamy bokeh. Pentax scores higher in color depth (23.5 bits vs. Olympus N/A) and dynamic range (13 EV vs. Olympus N/A on DxO Mark data), reflecting richness in tone transitions and detail recovery from shadows or highlights.

But don’t discount Olympus yet. Its TruePic VIII processor brings efficient noise management at higher ISOs up to 25600 native sensitivity. The sensor also uses an anti-alias filter, which slightly softens images but reduces moiré - great for landscapes or cityscapes with repetitive patterns.

Pentax’s lack of an anti-alias filter means razor-sharp details but exposes you to occasional moiré artifacts, which serious landscape or architectural shooters should manage through workflow correction.

In practice, I found Pentax has an edge when shooting in low-light indoor or astrophotography settings due to its sensor size and cleaner high ISO output. Olympus produces excellent results for street and travel photography, where portability paired with a versatile lens ecosystem compensates.

Autofocus and Performance: Speed, Tracking, and Accuracy in the Field

Nothing kills a moment faster than missed focus, so autofocus is paramount.

Olympus’s E-M10 IV features a contrast-detection-only AF system with 121 focus points utilizing on-sensor phase detection assist, allowing eye and face detection and even touch focusing on the rear screen. It maxes out continuous shooting at 8.7 frames per second - impressive for entry-level mirrorless.

Pentax K-S1 relies on traditional phase-detection AF with 11 AF points, some cross-type, designed to lock quickly even in dim light. It’s an older system but reliable for its class, shooting 5.4 fps continuous bursts.

In wildlife or sports shooting where fast-moving subjects dictate AF performance, Olympus’s advanced algorithm with more AF points offers better subject tracking and focus accuracy, especially with eye-detection. I tested bird-in-flight autofocus under overcast skies; Olympus kept higher keeper rates, while Pentax lagged behind, occasionally hunting for focus at critical moments.

On the other hand, Pentax benefits from optical viewfinder clarity and zero lag, helpful for precise manual focusing or when shooting fast-action under consistent lighting.

Build Quality and Weather Sealing: Toughness and Reliability Where It Counts

While neither camera is fully weather-sealed or ruggedized, Pentax slightly edges out in durability styling.

Both cameras lack environmental sealing, waterproofing, or crushproof certification, so neither will weather a rainstorm without extra protection. The Olympus feels solid but plastic-bodied, while the Pentax’s polycarbonate shell offers a more substantial grip.

Interestingly, Pentax DSLRs generally have a reputation for long-lifespan shutter durability and sturdy build quality, stemming from their DSLR lineage aimed at advanced amateurs and enthusiasts who favor reliability.

For professionals shooting outdoor landscapes, wildlife, or travel, Olympus’s lighter body means packing extra protective gear is easier, but Pentax’s robust handling inspires confidence in rougher shooting conditions.

Screen, Viewfinder, and Interface: Framing and Feedback When Every Second Counts

The E-M10 IV sports a bright 3.0-inch tilting touchscreen LCD with 1040k-dot resolution and a 2,360k-dot electronic viewfinder providing 100% coverage and 0.62x magnification.

Pentax K-S1 features a fixed 3.0-inch LCD with 921k-dot resolution (no touch) and an optical pentaprism viewfinder offering 100% field of view with 0.64x magnification.

Electronic viewfinders allow you to preview exposure and white balance adjustments in real time - great for instant feedback, especially in tricky lighting. Olympus’s tilting touchscreen also enables quick focus point selection by tap and reliable selfie mode, a boon for vloggers and casual videographers.

Pentax’s optical viewfinder offers pristine clarity with zero electronic lag or blackout, perfect if you love manual focusing or shooting during fast action sequences, though it lacks exposure preview.

The interface on Olympus is snappy and touchscreen-friendly, easing novice use. Pentax leans toward traditional DSLR menus and customizable buttons including illuminated controls, beneficial in dark environments but steeper on learning curve.

Lens Lineup and Ecosystem Compatibility: Options for Every Genre

Lens availability often steers system choice for career or hobby photographers with specific ambitions.

Olympus benefits from the mature Micro Four Thirds mount system with 107 lenses available, produced by Olympus and partners like Panasonic and Sigma. These range from compact wide-angles to high-quality telephotos and specialized primes, prized for portability and value.

Pentax’s KAF2 mount enjoys 151 lenses, including many excellent Pentax primes and APS-C and full-frame optics, with third-party support from Tokina and others. The larger APS-C sensor benefits from lenses designed for more medium-format style bokeh and image quality, albeit at greater size and weight.

Olympus’s smaller sensor multiplies focal length by 2.1x, so a 25mm lens acts like a 50mm equivalent, useful for telephoto reach on a budget but less ideal for shallow depth-of-field portraits.

Pentax’s 1.5x crop means 50mm lenses remain closer to classic portraits, delivering a more natural field of view and superior bokeh.

Battery Life and Storage: Keeping the Shots Coming

You don’t want your battery dying mid-hike or halfway through a wedding reception.

Olympus E-M10 IV claims approximately 360 shots per charge using the standard BLS-50 battery, with SD/SDHC/SDXC UHS-II card support.

Pentax K-S1 offers a slightly longer battery life of 410 shots, powered by the D-LI109 battery pack with a single SD card slot (SD/SDHC/SDXC supported).

In practice, battery life on both cameras depends on usage patterns - utilizing live view or EVF can drain mirrorless cameras faster. Olympus’s compact form factor lends itself well to carrying spare batteries, and some third-party grips are available for extended shooting.

Pentax’s DSLR-style battery tends to last longer due to optical viewfinder reliance, which consumes less power.

Connectivity and Video Capabilities: Modern Needs vs. Classic Strengths

While both cameras support basic video and wireless features, Olympus shines as the more modern, video-friendly option.

E-M10 IV offers 4K UHD video recording at up to 30fps with H.264 codec and linear PCM audio, alongside 1080p options up to 60fps. Unfortunately, there is no external microphone or headphone jack, limiting audio control for serious videographers.

Pentax limits video to Full HD 1080p at 30fps or below with H.264 encoding but boasts illuminated buttons, which help during video operation in dark scenarios.

For wireless, Olympus builds in Wi-Fi and Bluetooth, allowing instant image transfer and remote shooting via app - a major win for travel and social media photographers.

Pentax supports Wi-Fi indirectly through Eye-Fi card compatibility but lacks native Bluetooth or NFC.

Real-World Performance Across Photography Genres

To truly understand these cameras, I shot test sequences in the major photography styles enthusiasts care about:

Olympus E M10 IV front Olympus E M10 IV screen back Pentax K S1 front Pentax K S1 screen back

Portraiture

• Olympus delivers pleasing skin tones with its in-camera color profiles and effective face/eye detect AF. Its smaller sensor means less background blur at similar apertures - bokeh is decent but not dreamy. The effective 50mm equivalent lens makes portraits easy but less intimate.
• Pentax shines here - the APS-C sensor delivers smoother bokeh and richer tonal gradations, especially with fast primes. AF is accurate but slower to lock compared to Olympus.

Landscape

Pentax’s superior dynamic range and higher resolution make it superb for landscapes - fine details in shadows and highlights are retained with ease. Olympus performs well, especially combined with in-body 5-axis stabilization, but the smaller sensor limits extreme crops.

Wildlife and Sports

Olympus’s faster burst rate and denser AF points give it a clear edge for tracking erratic subjects. Pentax’s DSLR optical viewfinder helps maintain eye contact with fast action but struggles to keep up with autofocus speed, making it less ideal for serious sports shooters.

Street and Travel

Olympus’s compact size, light weight, and silent shutter mode win street photography hearts. Its touchscreen and wireless connectivity also fit modern travel workflows. Pentax’s larger body and weight can be cumbersome in crowded urban environments but offers durability and grip for longer outings.

Macro and Night Photography

Neither brand specializes in macro at this level, but Olympus gives an advantage with focus bracketing for stacking in post. For night and astrophotography, Pentax’s larger sensor and higher ISO capabilities yield cleaner noise handling and more detail retention in long exposures.

Video

Olympus delivers practical 4K video and touchscreen operation, suitable for casual videography. Pentax remains a still photography machine with basic HD video, not aimed at cinematographers.

Performance Ratings and Value Overview

Note: Ratings reflect combined lab measurements and in-field experiences.

Specialized Genre Scores for Different Photography Styles

Who Should Buy the Olympus OM-D E-M10 IV?

If you are a beginner or enthusiast valuing portability, ease-of-use, and modern conveniences like 4K video and wireless transfers - Olympus’s E-M10 IV is a compelling choice. For street photography, travel, casual portraits, and vlog-style video projects, it ticks many boxes without burning a hole in the wallet.

Its compact size and powerful in-body stabilization mean you can work with smaller lenses and less gear, a huge win when mobility is king. The 121-point contrast-based AF system with face/eye detection is impressively accurate for a camera in this price range.

However, if you demand superb low-light high ISO performance, longer battery life for all-day shoots, or razor-sharp portraits with classic DSLR bokeh, Olympus’s sensor size and lenses may feel limiting.

Who Should Opt for the Pentax K-S1?

Pentax lovers who hunger for a traditional DSLR feel, bigger APS-C sensor, and robust build quality will find the K-S1 rewarding. Photographers focusing on landscape, portraiture, and astrophotography should appreciate the dynamic range and image detail, especially when using the excellent Pentax lens lineup.

Its optical pentaprism finder offers one of the brightest and clearest views in this segment, and the sensor’s lack of anti-aliasing filter promises the sharpest images with well-chosen glass.

That said, the autofocus system is not built for speed or continuous shooting excellence. Its larger size and weight make it less convenient for travel or street photography, while limited video features and connectivity may disappoint hybrid shooters.

Final Thoughts: The Versatile Mirrorless vs. The Classic DSLR

In an era rapidly shifting toward mirrorless innovation, the Olympus E-M10 IV embodies the trend of compact, versatile cameras delivering respectable image quality with excellent handling.

Pentax’s K-S1, though introduced in 2014, remains a testament to DSLR reliability and superior sensor performance, especially valued by photographers who prefer optical viewfinders and traditional handling over touchscreen technology.

Your choice hinges on priorities:

• Go Olympus if you want a pocketable system with advanced autofocus, modern user interfaces, and video functionality for everyday creativity and travel.

• Choose Pentax if you want larger sensor quality, optical clarity, and classic DSLR ergonomics for serious landscape, portrait, and astrophotography work that prioritizes image quality over size.

Whichever you pick, both cameras offer surprisingly robust performance at their price points, and knowing their strengths ensures your photography adventures will be well-equipped and rewarding.

I hope this comprehensive comparison helps you cut through the noise and zero in on the camera that matches your photographic ambitions and shooting style. Happy shooting!