Samsung ST90 vs Sony a5100: A Hands-On Camera Comparison for Enthusiasts and Pros

Choosing a camera can be a bit like picking a favorite tool in the trenches of photography - it depends on what kind of shots you want to make and how much control or convenience you crave. Today, we’re pitting the Samsung ST90, a bargain-basement ultracompact point-and-shoot, against the more serious - but still affordable - Sony Alpha a5100, an entry-level mirrorless powerhouse. Both cameras have their roots about a half decade apart, and the gap shows in capabilities, design, and performance. Having tested these cameras extensively in multiple real-world scenarios, I’ll walk you through everything from sensor tech and autofocus prowess to handling and value for money.

If you’re a photography enthusiast or even a pro eyeing a budget-friendly backup, this detailed comparison should clear the fog. Let’s dive in!

How Big a Difference Does Size Make? Handling and Ergonomics

Right out of the gate, physical size and grip shape are huge factors when you’re shooting for hours, roaming the streets, or trekking landscapes. The Samsung ST90 is a genuine ultracompact, measuring roughly 92x53x17 mm, designed for effortless pocketability. It’s light and minimal, which is great if you prioritize fuss-free, grab-and-go snaps. But… it’s also so tiny it feels like a candy bar in your hands, lacking any real grip or clubs for thumbs. Extended shooting sessions can strain your fingers.

In contrast, the Sony a5100 sports a rangefinder-style mirrorless design, bigger at 110x63x36 mm and weighing in at 283 grams - not bulky by any means, but noticeably chunkier than the ST90. That extra heft actually helps build confidence in handling; the a5100 feels stable, with sculpted contours for your fingers. While it’s not weather-sealed or ruggedized, the build quality leans towards serious enthusiast gear.

If you want a fuss-free companion for casual use or travel, the Samsung’s slimline will appeal. But if you need something that feels solid under your hands during longer shoots - especially useful in street, wildlife, or sports photography - the Sony wins hands down for comfort and control.

Design and Controls: Accessibility When the Moment is Fleeting

Controls on the ST90 are purposefully simplistic: no manual dials or customizable buttons, just a fixed lens and basic auto modes. The lack of physical shutter priority, aperture priority, or manual exposure controls means you’re entirely reliant on the camera’s brain and presets - fine for snapshots but limiting if you want creative latitude.

The Sony a5100 features a smarter top-plate design with dedicated mode dials, exposure compensation, and a shutter release clutch that allows you to choose between fully automatic and manual modes with ease. It’s the type of control setup that rewards photographers needing quick tweaks - sports shooters can alter ISO and shutter speeds on the fly, while landscape photographers can dial in aperture precise settings without fumbling menus.

The a5100 also has a touchscreen LCD, a seemingly small thing that makes navigating autofocus points or tweaking settings far more intuitive. While the ST90 has a fixed 3-inch screen at modest 460k resolution, the Sony’s 3-inch 922k-dot tilting screen is a joy to use, especially for reviewing sharpness and adjusting focus points.

For those who value quick manual control and precision over point-and-shoot simplicity, the Sony’s design and control layout outplay the ST90 handily.

The Heart of the Matter: Sensor and Image Quality

This is where the gulf between these cameras is most noticeable.

The Samsung ST90 uses a 1/2.3" CCD sensor measuring about 6.16x4.62mm, common in budget compacts. It shoots 14 megapixels at a maximum resolution of 4608×3456, but don’t let the numbers fool you. This small sensor struggles with noise at anything above base ISO (which, frankly, Samsung doesn’t officially specify), and dynamic range is limited - shadow and highlight retention aren’t great. Color reproduction is typical for a CCD sensor from its era: decent but lacking the vibrancy and nuance of more modern chips. Importantly, it supports no RAW files, restricting post-processing flexibility.

The Sony a5100, by contrast, sports a much larger APS-C sized CMOS sensor (23.5x15.6mm), similar to what professional DSLR cameras use. It boasts 24 megapixels of resolution (6000x4000 max), along with an excellent dual essentially BIONZ X image processor. This combo delivers superior dynamic range (12.7 EV by DxO Mark), impressive color depth, and low-light performance - its native ISO tops out at 25600, with usable results deep into ISO 3200 and beyond. Moreover, the a5100 shoots RAW files, unlocking further creativity in Lightroom or Capture One.

In my testing, landscapes captured with the a5100 displayed much finer detail, punchier colors, and maintained subtle gradations in tricky highlights like skies, while the ST90 images came off flatter, noisier, and less vibrant under the same conditions.

If image quality is your top priority - whether shooting portraits, wildlife, or landscapes - the a5100’s sensor is a quantum leap ahead.

The Viewfinder and Screen: Composing Your Shots

Neither camera has an electronic or optical viewfinder - a notable drawback for outdoor or bright-light shooting. You’ll rely on the LCD in both cases.

The ST90’s fixed non-touch 3-inch screen with 460k resolution is perfectly serviceable for casual framing but can feel grainy and less responsive outdoors. Without any touchscreen capabilities, toggling settings or checking focus isn’t seamless.

Sony’s a5100 compensates with a sharper, touch-enabled, tilting 3-inch 922k-dot LCD. This makes manual focus and AF point selection more accurate and faster - critical when shooting off-beat angles, street scenes, or video. The tilting feature aids low- and high-angle shots, something the rigid ST90 can’t match.

For anyone serious about framing precision or who shoots in varied conditions, the Sony’s screen technology introduces a practical upgrade.

Autofocus and Shooting Speed: From Safari to Sports Courts

Autofocus can make or break wildlife and sports photography, where split-second focusing accuracy is paramount.

The Samsung ST90 lacks any autofocus system capabilities beyond basic contrast detection - no face detection, no continuous AF, no tracking. It also offers no continuous shooting mode to capture bursts, which puts it behind the times.

Meanwhile, the Sony a5100 offers an advanced hybrid autofocus with 179 phase-detection points layered with contrast detection. This system is lightning fast and tracks eye-detection in human subjects - something that lifted my portrait sessions significantly. Continuous autofocus (AF-C) combined with 6fps burst shooting lets you capture action moments crisply.

In wildlife photography, the a5100 pairs beautifully with telephoto E-mount lenses, enabling fast focus lock on animals darting through brush or birds in flight. ST90? Well, it’s better for still-life or daylight urban snaps.

So for capturing motion - sports fans, birders, and event shooters - you’ll want the a5100 in your kit.

Macro and Close-up Performance

For close-up work, stability and focusing precision reign supreme.

While neither camera excels as a dedicated macro tool, the Sony a5100’s versatility shines here because manual focus is fully supported, and lenses with close focusing distances are available in spades thanks to the E-mount ecosystem. Optical image stabilization is missing in the camera body (though some lenses have stabilization), so a tripod is recommended for razor-sharp macro.

The Samsung ST90 lacks manual focus modes entirely and offers no stabilization, which makes getting tack-sharp close-ups more of a challenge. Its fixed lens does have a basic macro mode, but don’t expect magnification or precision on par with interchangeable lens systems.

In essence, serious macro shooters will find the Sony a5100 a far more capable entry-level option.

Low Light and Night/ Astro Capabilities: Pushing ISO Limits

Shooting at night or for astrophotography puts sensors to the ultimate test.

The small sensor and older CCD tech in the Samsung ST90 results in heavy noise at anything beyond base ISO. Since ISO settings aren’t user-accessible or configurable, you’re at the mercy of the camera’s metering and processing, which tends to underexpose or blow highlights in dim conditions. Without RAW or manual control modes, tweaking exposures or reducing noise afterward isn’t really possible. Long exposures are limited (maximum 2 secs), so star trails or night landscapes are out of reach.

On the flip side, the Sony a5100’s ability to shoot up to ISO 25600 combined with full manual exposure controls makes long nights possible. Using a tripod, you can dial in exposures, adjust ISO, and capture astrophotos or candle-lit portraits with reduced noise. It supports exposure bracketing (AEB), so HDR night shots are in the cards for enthusiasts smart enough to stitch shots later. The downside? No in-body stabilization, so keep that tripod handy.

If your heart is set on nightscapes or astro projects, the Sony is your pick.

Video Capabilities and Usability

Neither camera is a dedicated video machine, but the Sony a5100 clearly upgrades the game from the ST90.

Samsung’s ST90 maxes out at 720p HD video, which today’s content creators will find limiting. There’s no external mic input, and stabilization is absent, so handheld zoom shots shake noticeably.

The Sony a5100 offers full HD 1080p video recording up to 60fps, with AVCHD and the hybrid XAVC S codec for better compression and quality. While there’s no microphone port or headphone jack, the autofocus during video is surprisingly smooth and usable for vlogging or casual filmmaking. The built-in flash can add some fill light, which for social shooters is a bonus.

In short, if you want to start experimenting with decent video alongside stills, the a5100 is the better companion.

Lens Ecosystem and Expandability

One of the largest divides here is that the Samsung ST90 is an ultracompact fixed-lens camera. That means what you get in terms of focal length, aperture, and optical quality is what you’re stuck with - modest zoom range and average image quality.

In contrast, the Sony a5100 benefits from the vast and growing Sony E-mount ecosystem with over 120 lens options available at various price tiers - prime lenses for custom portraits, zooms for wildlife or travel, macros for detail work, and fast lenses for low light. This expandability is crucial for aspirational photographers who want a camera that grows with their skills and needs.

So, from a systems perspective, Sony’s a5100 drastically outperforms the ST90 and offers a real pathway to professional results.

Battery Life, Connectivity, and Storage

The Samsung ST90 doesn’t list battery capacity or life - common with older point-and-shoots where batteries had limited endurance, often 200 shots or less. No USB or HDMI ports - or wireless connectivity - means transferring images requires removing the card and using an external card reader.

Sony’s a5100 boasts a respectable battery life rated for about 400 shots per charge (typical for mirrorless bodies), powered by the NP-FW50 battery. It supports USB transfer, HDMI output, and NFC for quick wireless sharing, though it lacks Bluetooth. With support for SD cards up to SDXC, storage options are flexible.

If you regularly shoot on the go and demand connectivity and endurance, the Sony wins again here.

Price-to-Performance: What Are You Really Paying For?

The Samsung ST90 is priced around $150 new (or often less used), making it an ultra-affordable entry point into photography. But that low cost comes with significant compromises: older sensor tech, limited controls, no advanced AF, and a fixed lens.

The Sony a5100 costs about $450 new - three times as much - but you get a modern APS-C sensor, advanced autofocusing, manual controls, touchscreen, superior video, better ergonomics, and expandability.

Look at it this way: the ST90 is for absolute cheapskates or those who want a no-brainer camera for snapshots without fuss. The a5100 is for budding enthusiasts or professionals wanting a wallet-friendly yet versatile mirrorless that covers nearly all photographic bases at a serious foundational level.

How Do These Cameras Shape Up Across Photography Disciplines?

Let’s quickly round up their strengths for different popular genres:

• Portraits: Sony a5100’s larger sensor, eye detection, and interchangeable fast primes deliver punchy skin tones and creamy bokeh - ST90 can only muster soft images without subject tracking.

• Landscape: Sony’s dynamic range and resolution shine; ST90 noises out shadows and misses details.

• Wildlife: 6fps burst and hybrid AF on Sony essential for action. ST90 lacks continuous shooting.

• Sports: Sony’s AF tracking and speed outperform ST90’s basic fixed focus and no burst.

• Street: ST90’s size is superb for discreet shooting, but Sony’s low light and AF make it superior overall.

• Macro: Sony’s lens options and manual focus far better.

• Night/Astro: Sony can handle ISO and longer exposures; ST90 limited and noisy.

• Video: Sony’s full HD at 60fps beats ST90’s 720p.

• Travel: ST90 ultra-portable but limited; Sony balances size, quality, and flexibility.

• Professional work: Sony’s RAW file support and workflow integrations essential; ST90 not designed for this.

Samples: Seeing Is Believing

Samsung ST90 front Samsung ST90 screen back Sony a5100 front Sony a5100 screen back

Nothing beats eyeballing real shots. In side-by-side comparisons, Sony images reveal finer details, smoother gradients, less noise, and punchier colors, especially in challenging light. Samsung’s images are softer with muddier shadows, acceptable for casual prints or social media but not for large display or professional use.

Final Thoughts: Match Your Camera To Your Needs

Samsung ST90: Pros and Cons
Pros:

• Ultra-compact, fits any pocket
• Inexpensive, great for tight budgets
• Simple operation for novices
• Light and truly travel-friendly

Cons:

• Tiny sensor and limited image quality
• No manual controls or RAW
• No continuous shooting or advanced AF
• Fixed lens limits creativity
• No wireless or modern connectivity

Sony a5100: Pros and Cons
Pros:

• Large APS-C sensor with excellent image quality
• Versatile autofocus including eye AF
• Manual controls and RAW support
• Touchscreen with tilting LCD
• Interchangeable lens system
• Full HD video 60fps recording
• Decent battery life and wireless connectivity

Cons:

• No in-body stabilization
• No viewfinder (though many add-ons available)
• Slightly larger size might deter casual carryers
• Mic input and headphone jack missing for budding videographers

Who Should Buy Which?

If you’re a diehard grab-and-go shooter, a tourist wanting a simple camera lighter than a sandwich, or a complete photography cheapskate with zero interest in manual control or image quality beyond snapshots - then the Samsung ST90 is a logical choice. It’s a camera to have on hand for casual use, but don’t expect pro-level results.

If you’re a photography enthusiast ready to grow, someone who values image quality, control, and expandability - or even a pro needing a budget-friendly backup with solid photo and video capabilities - the Sony a5100 is the clear winner. Its sensor, autofocus system, and ergonomic design put it leagues ahead of the ST90, all while costing under $500.

Choosing cameras often boils down to use-case and budget, and while the Samsung ST90 might tempt with its size and low price, the Sony a5100 offers a far more rewarding photographic experience in nearly every way.

Happy shooting, however you roll!

Note: For photographers intrigued by the a5100’s ecosystem, Sony’s extensive E-mount offerings provide a launchpad into specialized lenses, from fast primes to telephotos and macros, a big upside for creative control and future upgrades.