Sigma DP1 vs Sony A55

Sigma DP1 vs Sony SLT-A55: An Expert Comparison of Two Distinct APS-C Cameras

In the broad landscape of APS-C sensor cameras launched in the late 2000s and early 2010s, the Sigma DP1 and Sony SLT-A55 represent two polar approaches to image-making. The Sigma DP1 marks a bold experiment in compact large-sensor photography with its fixed-lens design centered on image quality above all, while the Sony SLT-A55 emerges as a versatile entry-level DSLR alternative incorporating innovative SLT mirror technology, robust autofocus, and video capabilities. This detailed comparison explores these cameras from the standpoint of photographers and imaging professionals who demand nuanced, practical insights grounded in extensive experience with mid-tier APS-C cameras.

Design and Ergonomics: Compactness versus Handling

The Sigma DP1, classified as a large sensor compact, targets portability with a physical footprint of 113x60x50 mm and a lightweight body at just 270 grams. Its unassuming profile makes it an unobtrusive tool for travel or street photographers prioritizing discretion and mobility. The fixed 28 mm equivalent lens further simplifies the user experience but limits compositional flexibility.

Conversely, the Sony A55 occupies the space of a compact SLR, with dimensions of 124x92x85 mm and a heftier 500-gram body. The deeper grip and larger physical presence lend themselves better to controlled handling, especially with longer lenses. This design benefits users engaged in extended shooting sessions, such as wildlife or sports photographers, who require stability and physical control.

While the DP1 lacks a viewfinder entirely, the Sony A55 employs a 100% coverage electronic viewfinder, supporting precise framing and exposure assessment in bright environments where LCD screens falter. This difference influences usability deeply depending on shooting conditions and preferences.

Sony’s more traditional DSLR-style button layout offers a higher degree of tactile control, with a 3-inch articulating screen, advantageous for shooting at awkward angles. The Sigma’s fixed 2.5-inch LCD with modest 230k-dot resolution restricts composability and user interface interactivity. The absence of touchscreen capabilities in both cameras makes reliance on traditional dials and buttons obligatory.

Sensor Technology and Image Quality: Foveon X3 Versus Conventional CMOS

A defining characteristic differentiating these cameras is their sensor technology. The Sigma DP1 showcases a Foveon X3 APS-C sized sensor (20.7 x 13.8 mm), a unique CCD-derived design capturing color information across three layers of pixels, theoretically yielding superior color fidelity and micro-detail rendition. However, the resultant 5-megapixel resolution (2640x1760) is modest by contemporary standards, impacting output size and cropping flexibility.

Sony’s A55 features a more conventional 16MP (4912x3264) CMOS sensor sized at 23.5x15.6 mm, offering greater pixel count and thus higher resolution images suitable for large prints and cropping demands. Furthermore, this sensor accommodates expanded ISO ranges (native 100-12800, extendable to 25600), greatly surpassing the DP1’s ceiling at ISO 800.

Testing in controlled environments indicates the Foveon sensor’s advantage in color depth and tonal smoothness at base ISOs, exhibiting excellent differentiation in mid-tone flesh tones and natural hues - a boon for portrait work. However, it reveals limitations in dynamic range and low-light performance, with increased noise and reduced sharpness at higher ISOs and complex lighting scenarios.

In contrast, the Sony A55’s CMOS sensor delivers a wider dynamic range of 12.4 stops (per DxO Mark), balanced color reproduction, and superior performance in low-light conditions with cleaner files at ISO 1600 and beyond. This broadens creative latitude, especially for landscape, event, and sports photography, where lighting conditions are variable.

Autofocus Systems and Focusing Performance

Sigma’s DP1 relies exclusively on contrast-detection autofocus with no dedicated autofocus points or face detection capabilities. Focus acquisition is single-shot only with no continuous tracking or subject recognition mechanisms. In practice, this translates to longer autofocus times, difficulty locking focus in low contrast or dim environments, and limited suitability for capturing fast-moving subjects, such as wildlife or sports.

In direct contrast, the Sony A55 employs an advanced hybrid autofocus system integrating 15 phase-detection points and full contrast-detection in live view. This combo yields swift, accurate AF acquisition with reasonable tracking ability - albeit with some limitations in continuously following erratic subjects compared to higher-end Sony models. Additionally, the A55 supports face detection autofocus, increasing focus accuracy on human subjects in portrait or street photography contexts.

This combination makes the Sony much more versatile, particularly for photographers requiring responsive AF performance, including wildlife and sports shooters.

Build Quality, Weather Resistance and Durability

Neither camera features significant environmental sealing or professional-grade protections such as dust, moisture, or freeze resistance. The DP1’s compact and lightweight magnesium alloy body emphasizes portability over ruggedness. Its fixed lens and minimal mechanical complexity reduce points of potential failure but also limit expansion.

Sony’s A55 construction is more robust, with a polycarbonate chassis mounted onto a metal frame, offering greater durability during demanding shoots. While lacking weather sealing, the thicker grip and reinforced design provide improved handling resilience. For photographers requiring durable construction for outdoor, travel, or professional use, the Sony’s build is preferable.

Ergonomics and User Interface: Screen and Viewfinder Analysis

The Sigma DP1’s fixed 2.5" LCD provides minimal 230k dot resolution, constraining image review fidelity and live preview utility. Its lack of touchscreen limits quick adjustments and menu navigation, detracting from user workflow efficiency. Moreover, without any viewfinder, composing in bright daylight becomes cumbersome.

The Sony A55’s 3-inch fully articulating screen with a dense 921k-dot resolution improves composition versatility, allowing shooting at ground level or above crowds. This enhanced interface aids macro and street photographers relying on unconventional angles.

Notably, the A55’s electronic viewfinder renders 100% frame coverage at 1150 dots, providing a considerably better framing and exposure monitoring environment. This is essential for accurate portrait, wildlife, and sports photography work, where precision framing determines image quality.

Lens Ecosystem and System Expandability

The Sigma DP1’s fixed lens arrangement – a 28 mm equivalent (1x crop factor applied, given sensor specifics) – constrains versatility to wide-angle perspectives only. While the lens is optically sharp and well suited for landscapes and environmental portraits, users requiring telephoto, macro, or variable zoom will find this severely limiting.

Sony’s A55 employs the Sony/Minolta Alpha mount supporting a wide array of 143 native lenses spanning prime, zoom, macro, and specialty optics. This expansive lens ecosystem enables users to adapt to virtually any photographic discipline, including wildlife telephoto work, studio portraiture, macro photography, and dynamic sports shooting.

Burst Shooting and Video Capabilities

The Sigma DP1 does not support continuous shooting or any video recording capabilities, limiting its appeal for dynamic and multimedia-oriented photographers. It was designed primarily as a still photography device prioritizing image quality in static scenarios.

In contrast, the Sony A55 has a substantial 10 fps burst shooting mode with autofocus locked on the first frame - respectable for an entry-level SLR of its era - enabling sequences of sports, wildlife, and action photography.

Moreover, the Sony supports HD video recording at full 1080p (up to 60fps), with useful codecs like MPEG-4, AVCHD, and H.264, a microphone input jack for external audio sources, and mini HDMI output. These features cater to multimedia storytellers and hybrid shooters needing both stills and videos from a single platform.

Battery Life and Storage

The Sigma DP1’s battery life specifications are not well documented but tend to be short given the compact design and lack of power-saving technologies. Its single SD/MMC card slot provides standard storage without redundancy or backup options.

Sony A55 offers significantly longer endurance, rated for approximately 380 shots per charge using the proprietary NP-FW50 battery pack, adequate for full-day shooting sessions. Storage flexibility is enhanced by compatibility with SD, SDHC, SDXC, and Memory Stick types, supporting faster write speeds and larger media volumes.

Connectivity and Wireless Features

Unsurprisingly for a compact from 2008, the Sigma DP1 offers no wireless connectivity or modern data transfer protocols, limiting tethering and immediate sharing options.

Sony’s A55 integrates Eye-Fi card compatibility, allowing limited wireless image transfer and management, along with USB 2.0 and HDMI output options, improving workflow integration with PCs and external displays. There is no built-in WiFi or Bluetooth, common in more recent models, which restricts real-time remote shooting or advanced connectivity needs.

Price and Value Assessment

At launch and as of historical pricing references, the Sigma DP1 was marked at approximately $566, centering on a niche audience seeking exceptional picture quality from a compact device without interchangeable lenses.

Sony’s A55 lists near $800 body-only, reflecting its broader features, faster performance, and system expandability. While costlier, the Sony model offers a more complete photographic experience for enthusiasts and beginners progressing into serious DSLR work.

Sample Images and Performance in Real-World Disciplines

Sigma DP1 front Sigma DP1 screen back Sony A55 front Sony A55 screen back

Portrait Photography:

• Sigma DP1: Exceptional color depth and skin tone rendition owing to the Foveon sensor’s unique color capture, delivering smooth tonal gradation and pleasing bokeh from the fixed wide lens when shooting close-ups. Its limited resolution restricts large prints or heavy cropping.

• Sony A55: Higher resolution delivers crisp facial details, bolstered by face detection autofocus and better subject tracking. Interchangeable lenses allow use of dedicated portrait primes with wider apertures, creating more aesthetic bokeh and shooting flexibility.

Landscape Photography:

• DP1: The fixed wide 28mm equivalent lens suits landscapes, and sensor color accuracy is strong; however, dynamic range is modest, limiting highlight retention in harsh lighting. No weather sealing should temper use in adverse conditions.

• A55: Greater resolution and dynamic range capture finer details and wider tonal latitude. Articulated screen helps low-angle compositions. Lens interchangeability spans ultra-wide to telephoto landscape setups. No environmental sealing remains a consideration.

Wildlife and Sports:

• DP1: Not designed for action; slow contrast autofocus and no burst mode hamper capturing fast subjects.

• A55: 10fps burst, 15 phase-detection AF points, and face detection afford decent action shooting at entry-level. Compatible with telephoto lenses critical for wildlife.

Street Photography:

• DP1: Compact size and quiet operation favor street candid shooting. Manual focus and limited AF autonomy require patience. Fixed lens limits framing options.

• A55: Larger body less discreet but better autofocus and articulating screen support varied street environments. Faster burst allows capturing fleeting moments.

Macro and Close-up:

• DP1: No dedicated macro focusing or lens capability.

• A55: Compatible with macro lenses and offers focusing aids suitable for close focus precision.

Night and Astro:

• DP1: Low maximum ISO 800 and lack of stabilization restrict low-light shooting.

• A55: Extended high ISO range and sensor stabilization enable better night photography and video.

Video:

• DP1: No video functionality.

• A55: Full HD video, mic input, and stabilizing sensor position it as a competent hybrid tool.

Travel:

• DP1: Ultra-portable with strong still image quality; lens limitation may be restrictive.

• A55: Larger but more versatile, longer battery life, and wider system adaptability better suit diverse travel needs.

Professional Workflows:

• DP1: Limited by slow data throughput (USB 1.0), absence of wireless, and modest resolution; suited for specialized artistic endeavors.

• A55: Supports RAW and multiple card formats, with USB 2.0 and HDMI connectivity facilitating streamlined tethering and post-processing integration.

Detailed Performance Ratings Overview

The Sony A55 aggregates considerably higher on key performance metrics such as autofocus speed, image resolution, video capability, and low-light usability, registering a DxOMark Overall Score of 73. In contrast, the Sigma DP1 remains untested in contemporary benchmarks but is understood to excel in color accuracy and tonal quality, albeit with fundamental limitations in speed, resolution, and sensitivity.

Genre-Specific Performance Breakdown

• Portraits: DP1 favored for color fidelity; A55 excels in focus and detail.

• Landscapes: A55’s wider dynamic range and lens options provide an advantage.

• Wildlife/Sports: A55 enables action photography; DP1 unsuitable.

• Street: DP1’s small size preferred; A55 offers speed and versatility.

• Macro: A55 supports macro lenses; DP1 does not.

• Night/Astro: A55’s ISO and stabilization superior.

• Video: Exclusively the domain of the A55.

• Travel: DP1 is ultra-light; A55 more adaptable.

Conclusion and Recommendations

The Sigma DP1 occupies a distinct niche emphasizing color quality and compact portability but at the expense of versatility, speed, and sensitivity. It may appeal to photographers focused on fine art portraiture or landscapes in stable lighting conditions, valuing image tonality over megapixel counts and autofocus speed. The single fixed lens and absence of video make it unsuitable for dynamic or multimedia demands.

The Sony A55 provides a comprehensive, flexible photographic platform better aligned with enthusiast users needing speed, autofocus precision, lens versatility, and video capabilities. Its compromises lie in bulk, moderate build robustness, and dated wireless features. However, these are counterbalanced by practical advantages in workflow integration, exposure control, and subject tracking.

For photographers prioritizing pure image quality and portability, accepting slower operation and fixed focal length constraints, the Sigma DP1 remains a creative option.

For those requiring an all-around camera suited to varied genres, fast action capture, video, and system expandability, the Sony A55 presents a far more capable and enduring investment.

This in-depth analysis draws on methodical testing protocols used over thousands of cameras evaluated in studio comparisons and field trials, ensuring well-founded conclusions applicable to real-world photographic decision making.