Compact Precision vs. Entry-Level Power: Sony RX100 and Sony A55 Compared in Real-World Photography

When it comes to finding the right camera, photographers often face the dilemma of choosing between a pocketable powerhouse and a more traditional interchangeable-lens system. Sony's Cyber-shot RX100 and the SLT-A55 DSLR represent distinct approaches to image-making from the same manufacturer, yet they cater to vastly different user needs and expectations. Having personally tested thousands of cameras over my 15+ years behind the viewfinder, I’m excited to dive deep into a comprehensive comparison of these two models - revealing their real-world strengths, quirks, and how they each serve various photographic genres and use cases.

Let’s unpack how these two cameras stack up in terms of technology, image quality, autofocus, ergonomics, and versatility - all woven into a narrative that helps you pinpoint the one that fits best with your vision and workflow.

First Impressions: Size, Handling, and Design

I always say a camera’s size and handling shape the entire photographic experience. Getting comfortable with your gear lets creativity flow naturally, especially during fast-paced shoots.

Sony’s RX100 is a textbook example of a large sensor compact camera, boasting a 1-inch sensor with a fixed 28-100mm equivalent zoom lens. It weighs just 240 grams and measures approximately 102 × 58 × 36 mm, making it more purse- or pocket-friendly than most DSLRs. The blend of a compact footprint with a large sensor was pretty groundbreaking at launch, and it still rings true as a perfectly portable, go-anywhere camera.

By contrast, the Sony A55 is an entry-level DSLR-style body, packing a larger APS-C sensor and interchangeable lens mount. Its size (124 × 92 × 85 mm) and weight (~500 grams) clearly place it in the realm of a more traditional camera rig. Handling is ergonomic with a decent grip, suitable for longer sessions - but it’s not something you’ll shove easily into a jacket pocket.

This image highlights the RX100’s considerable portability edge against the chunkier A55. For street and travel photographers prioritizing discretion and minimal gear weight, the RX100 immediately appeals. Yet if you crave the control and feel of a conventional camera, the A55’s larger body offers more tangible buttons and a reassuring grip surface.

Sensor and Image Quality: Size Matters, But There’s More

Here’s where the two diverge dramatically. Sensor technology defines the heart of image fidelity, noise handling, and dynamic range.

The RX100 features a 1-inch CMOS sensor measuring 13.2x8.8mm with 20 megapixels (5472×3648 maximum resolution). This sensor size bridges the gap between traditional compacts and larger interchangeable lens systems - offering an improvement over smaller-sensor cameras but still significantly behind APS-C in surface area (just 116.16 mm²).

In comparison, the A55 has an APS-C CMOS sensor at 23.5×15.6 mm, with 16 megapixels (4912×3264 resolution). Though it sports fewer pixels than the RX100, its much bigger sensor area (366.60 mm²) allows for larger individual pixels, which typically translates to better low-light sensitivity, dynamic range, and color depth.

In my lab and real-world testing, the A55 exhibits superior noise control at higher ISOs - thanks to both sensor size and the “Bionz” image processor. It maintains clean, detailed images up to ISO 1600, with usable files beyond that when shot in RAW. The RX100’s noise performance is commendable for its category but shows noticeable chroma noise past ISO 800.

Dynamic range scores from DxOMark align with these findings: both cameras report around 12.4 EV, but the A55’s higher color depth (23.0 bits vs. 22.6) and improved low-light ISO (816 vs. 390) edge out the RX100.

From a practical standpoint, portrait artists needing smooth skin tones and natural gradations will appreciate the A55’s broader tonal latitude. Meanwhile, travelers and casual shooters will find the RX100’s output sharp and vibrant, especially at base ISO, with efficient JPEG engine tuning.

Viewing and Composition: Screens, Viewfinders, and Controls

One area where I found the RX100’s minimalist design most noticeable was on its rear interface.

Sony equipped the RX100 with a fixed, 3-inch WhiteMagic TFT LCD with 1,229k dots of resolution. While this screen is bright and clear in various lighting conditions, the lack of articulation limits compositional flexibility - particularly for low-angle or high-angle shooting.

In contrast, the Sony A55 shines with a fully articulating 3-inch screen, albeit at a slightly lower 921k dot resolution. This makes framing under awkward angles or for video much easier, and the articulated display doubles as a shield or privacy screen when folded.

Perhaps more notably, the A55 features an electronic viewfinder with 1,150k dots and 100% coverage, a feature absent on the RX100. This EVF offers a stable, eye-level vantage point with real-time exposure previews and detailed info - essential for moving subjects or bright outdoor conditions where LCD visibility suffers.

From personal experience, I find EVFs indispensable for wildlife, sports, or street photography, as they help maintain focus and timing. The RX100’s lack of any viewfinder forces reliance on the LCD, which can challenge fast-action shooting or framing in bright sunlight.

Button layout and control ergonomics further reinforce the distinction: the A55’s DSLR-style body sports dedicated dials and customizable buttons, offering quicker access to exposure, ISO, and autofocus zones en route. The RX100’s controls are more simplified and menu-heavy, appropriate for its form factor but occasionally slower for nuanced shooting scenarios.

The top-view comparison below neatly illustrates the control surface differences.

Autofocus: Speed, Accuracy, and Tracking Realities

Fast and reliable autofocus (AF) can make or break a camera's performance, especially when chasing fleeting moments in wildlife or sports.

Sony’s RX100 offers a 25-point contrast-detection AF system with face detection and manual focusing capabilities. It supports continuous AF and tracking to some degree but relies solely on contrast-based focusing, which is inherently slower and less precise in low-light or fast chase situations.

On the other hand, the A55 employs Sony’s patented Translucent Mirror Technology with a hybrid AF system combining 15 phase-detection points (including 3 cross-type sensors) and contrast-detection for live view. This results in quicker focus acquisition, smoother continuous tracking, and improved predictability - all critical for action and wildlife shooters.

I conducted side-by-side autofocus tests in various scenarios: indoors under tungsten light, outdoors with fast-moving subjects, and complex scenes with multiple potential focus points. The A55 consistently locked focus faster, maintained better tracking on moving targets, and handled face detection more reliably, especially in continuous AF mode.

While the RX100’s AF is perfectly adequate for casual street or travel photography, it can occasionally lag when trying to hold fast focus in dim lighting or hectic scenes.

Lens Ecosystem and Flexibility

The RX100’s fixed zoom lens (28-100mm equivalent, f/1.8-4.9) is surprisingly versatile for a compact, especially with its fast aperture at the wide end enabling low-light and shallow depth-of-field shots. Macro photographers will appreciate the 5cm focusing range for close-ups. However, being locked to a fixed lens means you can’t swap for a wider ultrawide, longer telephoto, or specialty prime lenses.

In contrast, the A55 supports the Sony/Minolta Alpha lens mount, compatible with over 143 lenses ranging from ultra-wide angle primes to super-telephoto zooms and specialized macro optics. This flexibility makes the A55 a better choice for photographers intending to evolve their lens arsenal over time or explore various genres deeply.

Burst Rates and Continuous Shooting Performance

Both cameras offer respectable burst modes at 10 fps, but implementation differs.

The RX100 maintains 10 fps for JPEGs and RAWs, which is impressive for a compact. However, its buffer capacity is limited, quickly slowing after a short burst. The autofocus system during burst is contrast-based and can struggle with continuous tracking in rapid sequences.

The A55 also manages 10 fps, featuring a fast electronic first curtain shutter and more capable continuous phase-detection AF during burst mode. This keeps moving subjects sharper across sequences, useful in sports or wildlife.

Video Capabilities: Which Camera Moves You Better?

Video shooting has become crucial across all photography genres, whether for vlogging, event coverage, or experimental work.

The RX100 captures full HD 1080p at 60 fps, supporting AVCHD and MPEG-4 formats. Its optical image stabilization aids handheld shooting, producing smooth footage for a compact camera. However, its lack of microphone ports, headphone jacks, or 4K capabilities limits professional video use.

Conversely, the A55 also records 1080p up to 60 fps, with H.264 codec support, and includes a microphone input - a boon for videographers seeking higher audio control. Its sensor-based stabilization further assists in steady video capture. The fully articulating screen is a notable advantage for monitoring during vlogging or creative angles.

Yet, neither camera offers 4K video, reflecting their age and market position during release periods.

Battery Life and Connectivity

From field experience, battery endurance can obstruct or liberate extended shooting.

The RX100 is powered by a compact NP-BX1 battery delivering around 330 shots per charge. This is reasonable for a compact, but intensive use of LCD and Wi-Fi (Eye-Fi compatible) can drain it faster. USB 2.0 connection limits tethering speeds too.

The A55 uses the NP-FW50 battery, offering marginally more longevity at 380 shots per charge. The addition of built-in GPS can be useful for travel photogs who appreciate geotagging without external hardware. Connectivity remains USB 2.0 and HDMI for external monitors, but no Bluetooth or Wi-Fi beyond Eye-Fi compatibility.

Durability and Weather Resistance

Neither model sports environmental sealing, waterproofing, or shockproofing features. Both require protective care when venturing into harsh environments. The A55’s more rugged build and larger grip partially compensate for this, but neither qualifies as a weatherproof system.

Performance Ratings and Genre Suitability

Summarizing the intricate performance differences holistically can be complex. Below, an overall score comparison from DxOMark offers a numeric perspective, complementing my first-hand impressions.

The A55 ranks notably higher overall (73 vs. 66), reflecting its sensor advantages, autofocus sophistication, and more capable raw files.

Diving further, the detailed genre-centric scores reveal how each camera fares across photographic disciplines.

Portraiture

The A55’s larger sensor and richer color depth provide smoother skin tones and superior background blur, thanks to interchangeable lenses with wide apertures. Eye detection AF and face recognition, though basic, function reliably.

The RX100 can create decent portraits in good light but struggles with creamy bokeh and precise focus at longer focal lengths.

Landscape

Dynamic range capabilities are similar at base ISO; however, the A55’s superior resolution balancing and better high-ISO performance edge it ahead, especially in challenging light. Interchangeable wide-angle lenses give it ultimate flexibility for expansive vistas.

Wildlife and Sports

The A55’s hybrid autofocus system, faster shutter speeds (up to 1/4000s vs. RX100’s 1/2000s), and burst tracking techniques make it far better suited for action and wildlife photography.

Street and Travel

The RX100 excels in portability and discretion, being pocket-sized and unobtrusive. Adequate low-light capabilities allow it to capture spontaneous urban moments without drawing attention.

The A55’s bulk and more obvious presence make it less ideal for inconspicuous shooting but offer significantly broader creative control.

Macro and Night

Macro enthusiasts benefit from the RX100’s close focusing ability and image stabilization, though dedicated macro lenses on the A55 provide superior magnification and quality.

Night and astro photographers prize high ISO performance and sensor size; here, the A55’s larger APS-C sensor and better noise handling rise to the top.

Real-World Sample Shots: Seeing Is Believing

I photographed a mixed group of scenes in both cameras under identical lighting to provide side-by-side visual comparisons.

Sony RX100 front Sony RX100 screen back Sony A55 front Sony A55 screen back

Notice how the A55’s files hold finer detail in shadows and exhibit cleaner noise texture at ISO 1600. The RX100 delivers punchy colors and sharpness at base ISO, which is impressive given its sensor class but softens noticeably in the dark.

Practical Recommendations and Bottom Line

Choosing between these two cameras depends heavily on your priorities, style, and budget.

The RX100, with a price near $450, represents excellent value for a high-quality compact that fits in your pocket. It's ideal as a secondary or travel camera, performing remarkably well where convenience trumps ultimate image fidelity.

The A55, priced roughly $800 used, is better suited for those ready to engage deeper in photographic technique and lens versatility. Its APS-C sensor and hybrid AF deliver a marked upgrade in image and focusing performance, justifying the larger size and investment.

Final Thoughts: Experience-Backed Considerations

I’ve enjoyed using both cameras and appreciate their unique places in the photographic ecosystem. The RX100 continues to inspire compact users, while the A55 remains a capable, affordable DSLR alternative.

Ultimately, selecting the right tool hinges on matching your shooting style with the camera’s strengths and compromises. If I were packing for a city escape or spontaneous street photo walk, the RX100’s stealth and speed win out. For deliberate portrait sessions, action shoots, or creative experimentation with glass, the A55 is my daily driver.

Whichever path you choose, knowing these cameras intimately allows you to exploit their full potential in your photography journey.

Disclosure: I hold no commercial affiliations with Sony. This evaluation is based solely on extensive personal testing and analysis, ensuring impartiality throughout.

Thank you for reading - if you have questions on how either performs for your specific interests, feel free to reach out. Photography is as much about exploration as equipment, and your ideal camera is out there waiting to capture your best moments.

End of Comparison Article