Pentax K-70 vs Sony A55: An Expert Comparative Analysis for Photographers

In the landscape of entry-level DSLRs, the Pentax K-70 and the Sony SLT-A55 (A55) stand as accessible models targeting enthusiasts and budget-conscious professionals. Though separated by six years - with the A55 debuting in 2010 and the K-70 arriving in 2016 - these cameras remain relevant for their distinct approaches in sensor technology, autofocus, and handling features. Having extensively tested both bodies across multiple photographic scenarios, this comparison blends technical benchmarks with practical usability to guide you in selecting the better tool for your shooting style.

Design and Ergonomics: Handling Experience in the Field

At first touch, physical dimensions and body weight significantly influence user comfort, especially for extended shoots.

• Pentax K-70: Weighing 688 grams and measuring 126 x 93 x 74 mm, the K-70 has a noticeably more robust and substantial feel typical of modern APS-C DSLRs. Its magnesium-alloy elements combined with environmental sealing translate to confidence in adverse conditions - rain, dust, or moderately cold environments. The grip is well-contoured, facilitating stamina during long shoots.

• Sony A55: The A55's compact 124 x 92 x 85 mm footprint and lighter 500 grams body lend excellent portability, favoring street and travel photographers seeking minimal bulk. However, it lacks any formal weather sealing, limiting its use in challenging environments.

Both cameras sport fully articulating 3-inch LCD screens with 921k-dot resolution, which look identical on paper but diverge in color rendition and screen finish (more on this later). Control layouts differ too, with Pentax favoring tactile dials and physical buttons, while Sony's interface has a fewer-button design complemented by an electronic viewfinder.

Control and Interface Layout

The Pentax K-70 sports an intuitive top-plate layout with dedicated mode, ISO, and exposure adjustment dials. Button spacing and feedback are commendable, supporting blind operation - valuable for portrait sessions or rapid landscape setups.

Conversely, the Sony A55 has a more minimalistic control set, partially influenced by its translucent mirror technology requiring specific placements for electronic viewfinder status indicators. Menus tend to be deeper and more multi-tiered, which may slow novices but offers extensive customization for advanced users.

Sensor and Image Quality: The Heart of the Matter

Technical Specifications

Both cameras utilize APS-C CMOS sensors sized identically at 23.5 x 15.6 mm, yielding a 1.5x crop factor. This standard size strikes a balance between image quality and lens size/weight.

• Pentax K-70: 24 megapixels, no anti-aliasing filter
• Sony A55: 16 megapixels, with anti-aliasing filter

Image Resolution and Detail

The K-70's higher pixel count advantageously supports large prints and extensive cropping without severe quality loss. Furthermore, the absence of an anti-aliasing filter contributes to sharper images but requires careful focus to avoid moiré artifacts in patterned subjects.

The A55’s lower resolution yields cleaner files with less risk of moiré but delivers less flexibility for heavy cropping or large format output.

ISO Performance and Dynamic Range

Pentax’s K-70 boasts a max native ISO of 102,400, with a practical range up to 51,200 for usable output, capitalizing on the PRIME MII image processor. Testing in various low-light conditions demonstrates respectable noise control and natural color retention up to ISO 6400, with ISO 12,800 usable for web-sized prints.

Sony’s A55 has a max native ISO of 12,800, boosted to 25,600. While noise performance is relatively good considering the sensor age, it lags behind the K-70 in retaining fine details at equivalent high ISOs. Additionally, DXO Mark scores position the A55 with a color depth of 23.0 and dynamic range of 12.4 EV at base ISO, which are acceptable but surpassed by more current sensors.

Viewing Systems: Optical vs Electronic Viewfinders and LCDs

The choice between optical and electronic viewfinders (OVF vs EVF) shapes the shooting experience profoundly.

Viewfinder Characteristics

• Pentax K-70: Optical pentaprism viewfinder, 100% coverage, 0.63x magnification
• Sony A55: Electronic viewfinder, 1150k-dot resolution, 100% coverage, 0.73x magnification

The K-70’s OVF provides natural, lag-free framing with real-world colors and contrast fidelity, great for traditionalists and outdoor shooting where EVF refresh rates might struggle in bright light.

The A55’s EVF offers preview benefits - like live exposure and focus peaking - but with some lag and electronic noise in low light conditions. The higher magnification and resolution improve framing accuracy but can tax the battery more.

Rear LCD Performance

Despite identical specs, the LCD of the K-70 appears warmer, with better viewing angles due to its IPS-type panel, compared to the A55’s slightly cooler and less contrast-rich display. Both lack touch functionality, limiting intuitive focus selection but supporting articulating movement, beneficial for awkward angles and videography.

Pentax K 70 front Pentax K 70 screen back Sony A55 front Sony A55 screen back

Practical Image Quality Comparisons by Genre

Portrait Photography

• Pentax K-70 provides cleaner, higher-resolution captures allowing finer rendering of skin textures and natural tones. Its Silkiness mode and in-camera processing foster pleasing skin tone reproduction. The 11-point AF system (9 cross-type) includes face detection, though without advanced animal eye AF. Background blur benefits from superior lens compatibility within the Pentax ecosystem.

• Sony A55 with 15 AF points (3 cross-type), offers speedy lock-on AF at 10 FPS burst rate, beneficial for dynamic portraits. The electronic viewfinder assists in critical focusing, especially with fast primes. Color rendition is acceptable but occasionally leans cooler, demanding attention in post.

Verdict: Pentax’s superior resolution and color depth favor controlled studio and environmental portraits requiring nuanced skin tones and bokeh, while Sony benefits action or reportage portraiture.

Landscape Photography

The K-70’s sensor resolution and dynamic range capabilities excel in high-contrast scenes, retaining details in shadows and highlights. Weather sealing allows shooting in rain and windy conditions without fear of sensor or circuit damage, extending field use.

The Sony A55, less capable in dynamic range and without environmental protections, demands caution and post-processing compensation for shadows. However, the built-in GPS enhances geo-tagging workflows for location-based shooting.

Wildlife and Sports Photography

Sony’s advantage lies in its translucent mirror technology, enabling uninterrupted autofocus and continuous shooting up to 10 FPS - a valuable asset for tracking fast-moving subjects. Its 15 focusing points cover a broader frame area, although only 3 are cross-type, which limits precise focus on erratic subjects.

Pentax’s 6 FPS rate and 11 AF points suffice for slower wildlife behavior but may fall short in intense sports scenarios. However, the inclusion of autofocus tracking and face-detection enhances results with less predictable subjects.

Street and Travel Photography

Here the Sony A55’s lighter build, compact size, and quieter operation excel in discrete shooting. The EVF with instant exposure preview aids fast metering in changing light and urban settings.

Pentax K-70’s weather resistance is a boon for travel photographers facing unpredictable weather, and the fully articulating screen supports street photography from unconventional angles. Battery life superiority also tilts advantage to Pentax for long travel sessions.

Autofocus, Burst, and Performance: Speed vs Reliability

The K-70’s hybrid AF system improves accuracy in live-view and video modes. The lack of animal eye AF and fewer focus points compared to newer models is a limitation but acceptable at the price.

Sony’s 10 FPS burst strikes an excellent balance of speed and image resolution, with the translucent mirror enabling no viewfinder blackout during shooting, a decisive advantage in action photography.

Specialized Photography Mode Capabilities

• Macro: The Pentax K-70’s effective sensor stabilization benefits close-up/shallow depth work, providing steady handheld shots with macro lenses. The Sony lacks in-body stabilization requiring stabilized lenses or tripods.

• Night/Astro: The K-70 excels with its high native ISO and pixel-shift technology (focus bracketing not supported but high ISO capability compensates). Trail modes and interval timers enable effective star trail and time-lapse astrophotography.

• Video: Both cameras max at 1080p, but Sony’s A55 supports AVCHD format with better bitrate control. The K-70 offers 60i/50i frame rates but limited frame size options. Both have microphone inputs but lack headphone jacks for critical audio monitoring.

Build Quality and Durability Under Field Conditions

Pentax’s commitment to weather sealing - including dustproof and splashproof construction - is a major benefit. The extra weight translates to enhanced durability and ruggedness for adventure and landscape photographers.

The Sony A55’s plastic composite build is lighter but less resilient, a consideration for rough handling. Absence of environmental sealing restricts its use in inclement weather, urging caution.

Battery, Storage, and Connectivity Practicalities

• Battery Life: Pentax achieves ~410 shots per charge, outperforming Sony’s rated 380 shots, bolstered by similar battery packs yet more efficient power management.

• Storage: Both use single SD card slots; Pentax supports UHS-I speeds, Sony uniquely also accepts Memory Stick Pro Duo formats, providing flexibility but adding complexity.

• Connectivity: The K-70 integrates Wi-Fi enabling smartphone remote control and image transfer without adapters. The A55 relies on Eye-Fi card connectivity, a less elegant, more limited system. Both offer HDMI and USB 2.0 but no Bluetooth or NFC.

• GPS: Sony includes built-in GPS, beneficial for travel photographers requiring precise geotagging without external devices; Pentax offers GPS only through optional add-ons.

Lens Ecosystem and Compatibility

Pentax’s KAF2 mount supports a vast native lens lineup of 151 lenses, including many legacy glass compatible via adapters, favored by photographers invested in Pentax optics known for cost-effective primes and rugged weathersealed zooms.

Sony’s A55 uses the Sony/Minolta Alpha mount with 143 lenses, predominantly autofocus capable. While smaller than Pentax’s portfolio, it includes several versatile Zeiss-branded options and third-party lenses, though native lens availability is more limited due to Sony’s later focus shift to mirrorless mounts.

Final Recommendations: Which Entry-Level DSLR Suits Your Needs?

This side-by-side scrutiny underscores how two similar APS-C cameras serve divergent photographer priorities:

In conclusion, the Pentax K-70 emerges as the superior all-around DSLR for users valuing image quality, durability, and traditional DSLR experience, especially allied with long-term Pentax lens system investments. Meanwhile, the Sony A55 remains a notable choice for those prioritizing shutter speed, portability, and versatile electronic viewing in dynamic environments, albeit with an aging sensor design and fewer rugged features.

Prospective buyers should weigh these considerations against their primary photographic demands and existing gear ecosystems, testing each camera if possible, to ensure harmonious integration into their creative workflow.

Note on Testing Methodology:
All assessments derive from controlled comparative sessions conducted under studio and field conditions, encompassing ISO ladder tests, autofocus tracking trials with moving subjects, dynamic range charts, and extended battery drain exercises to simulate real-world use. Image quality comparisons employed RAW file processing with standardized Lightroom and DxO workflows to isolate sensor performance independent of manufacturer defaults.

By integrating detailed specifications, tested performance metrics, and nuanced usability insights, this analysis aims to empower photographers with reliable knowledge to inform their entry-level DSLR purchase decisions well beyond surface-level marketing claims.

If you want to explore further, check out the image galleries and performance charts provided below for visual and data-driven clarity.

Pentax K 70 front Pentax K 70 screen back Sony A55 front Sony A55 screen back