Head to Head: Canon EOS R3 vs Panasonic Lumix GH3 - Which Mirrorless Camera Wins?

When it comes to mirrorless cameras, the gap across generations and brands can sometimes feel like night versus day. The Canon EOS R3 and the Panasonic Lumix GH3, separated by nearly a decade and aimed at pretty different user bases, make for an intriguing comparison. I’ve spent a ton of time behind the viewfinders of both cameras, from studio portrait sessions to chasing wildlife and shooting fast-paced sports, so I’m excited to share how these two broadly different but very capable systems stack up against each other in real-world use.

Whether you’re a pro-level shooter looking for cutting-edge performance or a serious enthusiast interested in punchy video and solid value, this side-by-side will help you understand what you get - and what you sacrifice - with these two contenders.

First Impressions: Size, Build, and Ergonomics

You don’t have to pick up the cameras side by side to guess which weighs more, but seeing them side by side gives a better ergonomic perspective.

The Canon R3 is a beast - reflecting its status as a professional, full-frame mirrorless workhorse. It measures 150x143x87mm and weighs just over 1kg (1015g). This camera is designed for serious hands, with a solid grip and clubs for thumbs on the rear, offering intense handling confidence during prolonged shoots or rapid bursts.

In contrast, the Panasonic GH3 stands much smaller and lighter at 133x93x82mm and 550g. It’s a compact powerhouse in its own right, more travel-friendly, and significantly easier to toss in a day bag without tiring your arm. Ergonomically, the GH3 features a smaller grip and simpler control layout but still offers solid physical controls, with fully articulating screens on both bodies (more on screen quality later).

The Canon R3's control cluster is considerably more complex - dedicated buttons and dials for shutter speed, ISO, autofocus modes, and white balance, plus a top display for critical info. This design suits pros needing instant access and tactile precision. The GH3 focuses on essential controls accessible through fewer dials and a touchscreen menu, leaning towards versatility and ease for enthusiasts rather than extreme professional speed.

If portability and lightweight are your top priorities, the GH3 earns the point. However, if you’re prioritizing robustness and a professional feel, the R3’s heft will actually translate to greater steadiness and durability in the field.

Sensor Technology & Image Quality Showdown

This is where the gap truly widens. The EOS R3 sports a 24MP full-frame stacked CMOS sensor measuring 36x24mm, a cutting-edge sensor with excellent dynamic range (~14.7 stops as per DxO Mark) and impressive low-light capabilities (native ISO up to 102,400).

The GH3 relies on a 16MP Four Thirds sensor, substantially smaller at 17.3x13mm with a crop factor of around 2.1x. It yields decent image quality for its time but can’t match the low-light prowess or bit depth of the R3. Dynamic range clocks at 12.4 stops - respectable but noticeably behind Canon’s sensor.

What does this mean practically? For portrait and landscape photographers demanding sharp, noise-free files with excellent color depth, the R3 leads by a mile. It handles skin tones smoothly without resorting to aggressive noise reduction, captures rich detail even in shadows, and exhibits less chromatic aberration. On the other hand, the GH3’s sensor can show noise creeping in at ISO 800+ and offers softer gradations in high-contrast scenes, though it can still deliver punchy images in good lighting.

Both cameras employ anti-aliasing filters, which help minimize moiré at the cost of a slight resolution tradeoff - normal for professional cameras but worth noting if ultimate pixel sharpness is critical.

Autofocus Systems: Speed vs. Reliability

When it comes to autofocus, Canon’s R3 dazzles with a whopping 1,053 focus points employing hybrid phase-detection and contrast detection, with excellent eye, face, and animal eye tracking. My tests in bright and dim conditions showed razor-sharp focus in split seconds, with excellent tracking of moving subjects, whether a running athlete or a bird in flight.

The GH3 has a more modest 23 contrast-based autofocus points without phase detection. Its autofocus is decent for static subjects and moderately slow-moving scenes, but it lags considerably behind in continuous tracking - especially in low light or fast action.

This difference is pivotal if you photograph wildlife or sports, where split-second critical focus makes or breaks the shot. Street photographers, however, may find the GH3’s autofocus adequate if they are shooting in better lighting and aren’t obsessively chasing each frame.

Shooting Speed and Buffer Depth

Want big burst numbers? The GH3 surprisingly hits 20 fps, but here’s the catch - it holds for far fewer frames before slowing. The R3 shoots at 12 fps with the mechanical shutter but has a massive buffer thanks to its newer processing engine, letting you capture real-world bursts of up to 100+ frames (RAW) without hiccups.

For action and sports photographers shooting long bursts, this is a game changer. The GH3’s burst rate might look appealing on paper but falls short when the buffer fills.

Image Stabilization – Sensor-Shift vs None

Canon R3 has in-body 5-axis sensor-shift stabilization, which does wonders handheld and enhances video stability. Combined with stabilized RF lenses, you can comfortably shoot at slower shutter speeds without blur.

The GH3 lacks in-body stabilization, relying entirely on optical stabilization in lenses. This complicates macro or low-light handheld shots, restricting flexibility.

Display and Viewfinder Experience

Both cameras support fully articulating touchscreens - key for video shooters and creative angles. The Canon R3’s 3.2-inch screen delivers an impressive 1.62 million dots of resolution, providing sharp playback, accurate touch response, and a bright, clear image. Its OLED electronic viewfinder (EVF) sports a whopping 5.76 million dots, offering almost lag-free live view and a pleasingly large view.

In comparison, the GH3’s 3-inch OLED screen with 614k dots is noticeably less crisp, and the EVF resolution clocks in at 1.74 million dots. While perfectly usable, it feels a bit dated, especially when you’ve used a more modern viewfinder like the R3’s. The GH3 may cause some frustration in bright light conditions and lower magnification may affect precise manual focusing.

Video Capabilities: Serious Filmmaker or Basic Capture?

Here the GH3 has an advantage for 1080p shooters on a budget with solid AVCHD and H.264 codecs, up to 60p. Its video capture is good and was groundbreaking in its day, especially for aspiring filmmakers needing a smaller rig. Panasonic’s focus on video shines here, offering strong manual controls and camera profiles.

But the R3 is in a different league altogether. It films up to 6K in 60p RAW (6000x3164), and 4K at up to 120fps, delivering far more flexibility in post. It also supports advanced codecs like H.265 (HEVC), external audio inputs, and better built-in microphones.

If video is your bread and butter, the R3 justifies its price tag with professional-grade output, internal stabilization, and better heat management for longer, cleaner clips. The GH3 is a great beginner/still-shooter’s video camera but lacks 4K and the codec sophistication pros demand today.

Weather Sealing and Durability

Both cameras offer some level of weather sealing, but the R3’s construction is significantly tougher. While not crushproof or waterproof, Canon’s professional build can endure dust, moisture, and cold better than the GH3, which was “advanced” for its time but more vulnerable by today’s rugged standards.

For outdoor or travel photographers who shoot in challenging weather, this is an important factor favoring the R3.

Lens Ecosystem and Mount Matters

Canon R3 front Canon R3 screen back Panasonic GH3 front Panasonic GH3 screen back

The Canon EOS R3 uses the RF mount with 27 native lenses currently and a rapidly growing lineup. RF lenses are optically superb, with bright apertures and advanced stabilization. Canon also supports adapters for EF lenses, granting access to a massive professional lineup.

The GH3 uses the Micro Four Thirds mount, boasting an enormous 107 lenses from a multitude of manufacturers. These lenses range from affordable primes to versatile zooms, providing plenty of options for enthusiasts and pros alike. However, the smaller sensor and crop factor impact depth-of-field control and low-light ability.

If variety and affordability are important, the GH3’s Micro Four Thirds system is hard to beat. For absolute image quality and lens pedigree, the Canon RF system shines.

Battery Life and Storage Options

The R3’s beefy LP-E19 battery delivers roughly 760 shots per charge (CIPA rating), respectable given the huge sensor and EVF. It supports dual card slots (one SD UHS-II and one CFexpress Type B), providing flexibility and redundancy for professional workflows.

The GH3’s battery life is decent at ~540 shots, but it only has one SD card slot. This is a constraint for professional use, especially when quick card swaps or backups matter.

Connectivity: Modern Standards vs Legacy

Don’t underestimate the convenience of connectivity - Canon’s R3 packs built-in Wi-Fi, Bluetooth, GPS, HDMI, and USB 3.2 Gen 2 with 10Gbps transfer. This speeds offloading and tethering workflows significantly.

While the GH3 features built-in Wi-Fi (no Bluetooth or GPS) and HDMI, its USB 2.0 port and older wireless standards lag behind modern expectations.

Price and Value Analysis

Here’s the reality check: at a list price of around $6,000 (body only), the Canon R3 is a significant investment targeted at professionals or serious enthusiasts with deep pockets.

The Panasonic GH3, coming new at roughly $800 (and much less on the used market), caters to budget-conscious photographers and those entering advanced mirrorless photography.

Your decision depends heavily on your budget, intended uses, and whether you can sacrifice built-in modern conveniences for savings.

How They Perform Across Photography Genres

To make this nuanced, let’s look at how the cameras fare dealing with specific photography types, incorporating DxOMark and hands-on performance data.

Portrait Photography

• Canon R3:
  • Skin tones render beautifully thanks to full-frame color depth.
  • Eye and face detection are best-in-class.
  • The larger sensor creates smooth, pleasing bokeh.
• Panasonic GH3:
  • Skin tones are decent but smaller sensor limits shallow depth-of-field effects.
  • Face detection works well in good lighting.
  • Bokeh is harsher due to sensor size and lens choice.

Landscape Photography

• R3:
  • Exceptional dynamic range (14.7 stops) captures shadow detail superbly.
  • Weather sealing and large sensor resolution give an edge.
• GH3:
  • Adequate dynamic range (12.4 stops).
  • Smaller sensor reduces ultimate resolution and low-light latitude.

Wildlife Photography

• R3:
  • 12fps mechanical shutter bursts with deep buffer.
  • Advanced autofocus tracking and animal eye detection literally save shots.
• GH3:
  • Higher fps frame rate but limited buffer.
  • AF speed and tracking slower.

Sports Photography

• R3:
  • Responsive autofocus and precise tracking.
  • High ISO capability and fast shutter speeds.
• GH3:
  • Fast burst but accuracy suffers.
  • Lower native ISO performance.

Street Photography

• R3:
  • Larger and heavier, less discreet.
  • Outstanding low-light autofocus.
• GH3:
  • Compact, lighter, better for candids.
  • Lower noise performance under dim light.

Macro Photography

• R3:
  • In-body stabilization aids handholding macro lenses.
  • Reliable focus stacking and bracketing.
• GH3:
  • No stabilization.
  • Manual focusing trickier.

Night and Astrophotography

• R3:
  • Native ISO up to 102,400 with good noise control.
  • Long exposures and advanced sensor tech shine.
• GH3:
  • Max ISO 12,800, noisier images in darkness.

Video Capabilities

• R3:
  • 6K up to 60p and 4K at 120p, professional video codecs.
  • Mic and headphone jacks plus in-body stabilization.
• GH3:
  • 1080p max; no 4K.
  • Good microphone port, but older codecs.

Travel Photography

• R3:
  • Bulkier, heavier but highly versatile.
  • Dual card slots critical for serious trips.
• GH3:
  • Lightweight, pocket-friendly.
  • Limited weather sealing compromises.

Professional Work

• R3:
  • Top-end reliability, tethering, robust file formats.
  • Excellent support for RAW workflow.
• GH3:
  • Adequate for amateurs, casual pros.
  • Single card slot and dated specs could bottleneck high-end workflows.

Overall Performance Ratings

For a clear visual summary, see the overall DxO Mark scores alongside user experience from hands-on testing.

The expert scores echo real-world impressions - the Canon R3 delivers professional-grade image quality and speed, while the GH3 offers solid enthusiast performance with a fraction of the budget.

Pros and Cons at a Glance

Canon EOS R3

Pros:

• Superb autofocus system with animal eye detection
• Excellent full-frame sensor with high dynamic range and low noise
• Professional-grade 6K/4K video with advanced codecs
• Dual memory card slots with CFexpress support
• Robust weather sealing and build quality
• Large, bright EVF and touchscreen
• Sensor-shift 5-axis stabilization

Cons:

• Price tag that’s tough for most consumers
• Heavier and bulkier, less discreet
• Complex controls may overwhelm beginners

Panasonic GH3

Pros:

• Compact and lightweight design
• Fully articulated OLED touchscreen
• Large Micro Four Thirds lens ecosystem
• Fast 20fps burst for short spurts
• Affordable price for advanced mirrorless features
• Good video performance for 1080p

Cons:

• Smaller Four Thirds sensor limits image quality
• No in-body stabilization
• Less advanced autofocus, especially in low light or tracking
• Single memory card slot
• No 4K video support
• Older connectivity standards

Who Should Buy Which Camera?

If you’re a professional photographer or serious enthusiast who demands top-tier autofocus, exceptional image quality, high-speed continuous shooting, and video versatility - especially for wildlife, sports, or professional events - the Canon EOS R3 is well worth the investment. Its size, build, and price all reflect that premium position, but it rewards with performance few cameras can match.

For hobbyists, beginners stepping up their game, or content creators on a tighter budget who want a versatile system with good image quality, a vast accessory and lens catalog, and decent video for 1080p projects, the Panasonic GH3 remains surprisingly relevant despite its age. It's a lightweight, affordable introduction to mirrorless with charm and competence, especially if 4K video or extreme low-light aren't deal breakers.

Parting Shot: My Personal Take

I still fondly remember shooting with the GH3 on wildlife hikes and street strolls. Its small size and snappy burst rate made it fun and approachable. But I have to admit, after handling the R3 in fast-moving sports environments and studio sessions, it feels like stepping into the future. The difference in autofocus speed and reliability, sensor performance, and professional features is like night and day.

If you dream of a future-proof camera with wide-ranging professional use, the R3 is an investment that will serve well for years. If you’re a cheapskate or someone who shoots mostly daylight stills, travel, or casual video and prefers a small package, the GH3 still punches above its weight.

For more images and comparison samples, check out the following gallery:

Canon R3 front Canon R3 screen back Panasonic GH3 front Panasonic GH3 screen back

Thank you for trusting my hands-on experience to guide your decision-making. Feel free to reach out with any specific questions or shooting scenario dilemmas!

Happy shooting.

• Your camera-savvy buddy in the field