Canon EOS R5: AF Acceleration and Deceleration

Tracking: The Canon EOS R5 Mark II’s Flexible Zone AF System for Birds in Flight

Introduction

"Tracking birds in flight is universally regarded as one of the definitive tests of any camera autofocus (AF) system. The unpredictable, high-speed, and often erratic movements of birds—as they take off, glide, change direction mid-air, or land—demand not only fast initial acquisition but also seamless tracking through sharp acceleration and abrupt deceleration. The Canon EOS R5 Mark II, released in July 2024, positions itself among the most advanced tools for action and wildlife photographers, touting a major overhaul to Canon’s already respected autofocus engine, with critical improvements in deep learning subject detection, acceleration/deceleration tracking, and the user-customizable Flexible Zone AF. This report provides a comprehensive, state-of-the-art analysis of the R5 Mark II’s Flexible Zone AF system's handling of acceleration and deceleration during bird-in-flight scenarios. The discussion will include technical details, user and expert feedback, direct comparisons to both Canon R5 Mark I and leading competitors like the Sony A1 Mark II, and up-to-date insights from firmware developments and practical field use.

Flexible Zone AF Technical Specifications

The Canon EOS R5 Mark II introduces a sophisticated iteration of Canon’s Dual Pixel CMOS AF II system. At the core of flexible zone autofocus (AF) is a user-adjustable focusing area that dynamically auto-selects from a matrix of AF points within a custom-sized region, enabling both specificity and forgiveness—traits that are especially important when tracking erratic airborne subjects.

Flexible Zone AF can be configured in three distinct geometries (Flexible Zone 1: square; Flexible Zone 2: vertical rectangle; Flexible Zone 3: customizable) and covers a substantial portion of the image area—up to 90% horizontally and 100% vertically in auto selection modes. With 1,053 AF zones that can be subdivided into user-defined flexible zones, photographers can adapt the AF region to the anticipated flight path or behavior of their subject, such as a small diving bird or a large soaring raptor.

Crucially, Flexible Zone AF operates in tandem with other AF features:

• Deep Learning Subject Detection (Birds, Animals, Humans, Vehicles)

• Eye Detection AF (can default to animal, human, or auto modes)

• Servo AF: Continuously adjusts focus as the subject moves

• Whole Area Tracking Servo AF: AF system automatically switches AF points/zones as the subject traverses the frame

Compared to its predecessor, the R5 Mark II’s stacked 45-megapixel BSI CMOS sensor and the dual DIGIC X and DIGIC Accelerator processors enable far faster readout and data crunching. These underpin real-time subject analysis, broader dynamic tracking, and a higher frame rate AF refresh for tracking high-velocity subjects.

Acceleration and Deceleration Tracking Performance

Canon has placed particular emphasis on improving subject tracking through sudden changes in velocity, a frequent occurrence in wildlife and especially birds—whether a heron rocket-launches from still water, a swift darts erratically, or a hawk decelerates to land. The R5 Mark II incorporates expanded controls for both Tracking Sensitivity and Acceleration/Deceleration Tracking, which can be finely tuned to suit either gradual gliding or instant speed shifts.

• Acceleration Tracking

The R5 Mark II’s AF algorithms are optimized to maintain locked focus on fast-accelerating subjects. In practice, this is realized by increasing the Accel./Decel. tracking parameter toward the +1 or +2 end of the scale. Here, the camera anticipates and reacts to abrupt subject movement, such as the explosive take-off seen in songbirds or the rapid acceleration as a raptor pounces.

Anecdotal and review evidence supports Canon’s claims. DPReview field testers have noted the camera's ability to stay locked on to subjects through intense, sudden bursts of movement, highlighting both the improved sensor readout and enhanced algorithmic prediction as key contributors. In enthusiast forums, users note that the R5 Mark II often achieves consecutive strings of in-focus captures during challenging flight launches—sometimes maintaining “perfect focus for 90 frames in a row” even when tracking waterfowl launching toward the camera through visually cluttered scenes.

• Deceleration Tracking

The equally challenging task of focus retention as the subject stops sharply—such as when a bird lands, changes direction, or drops to a perch—relies on immediate deceleration tracking. The camera’s tracking parameter can be set to +2 for maximum responsiveness, helping the AF system avoid “overshooting” the focus past the subject as its velocity drops to zero. Conversely, settings further toward -1 or -2 enhance stability, ensuring focus is not prematurely switched due to momentary distractions or background elements.

Photographers focusing on landing or perching birds generally confirm improved performance compared to the original R5. The R5 Mark II is less likely to lose focus or “hunt” in these scenarios, especially when paired with optimized settings such as Responsive tracking and Whole-Area Servo AF enabled. Several reviews mention that even fast, zig-zag landing trajectories are handled with greater precision and a reduced number of out-of-focus frames than was common on older models.

• Customization and Case Manual vs. Auto

The R5 Mark II allows for manual configuration (“Case Manual”) of these parameters for users who want to optimize tracking for their particular bird subject or shooting style, or for “Case Auto” where the camera evaluates scene context and switches strategy dynamically. The ability to override settings via dedicated buttons (e.g., AF-ON customization) allows on-the-fly adjustment, an especially practical feature when tracking unpredictable wildlife that may suddenly change acceleration or deceleration patterns.

• AF Settings Optimization for Birds in Flight

Canon’s recommended approach for birds in flight is to use Servo AF combined with either Flexible Zone AF or Whole-Area AF for large flying birds, and Flexible Zone or smaller zones for smaller or more erratic subjects. Additional parameters are adjusted based on environmental complexity—such as using smaller Flexible Zones in cluttered backgrounds to reduce AF distraction from non-subject elements.

Canon and leading bird photographers often suggest the following typical settings:

• AF Operation: Servo AF

• AF Area: Flexible Zone AF (size / shape adjusted per scene)

• Orientation-Linked AF Point: Separated AF points for vertical vs. horizontal orientation

• Whole-Area Tracking Servo AF: On

• Subject Detection: Animals (Birds)

• Eye Detection: Auto

• Servo AF Characteristics: Case Auto (“0”) for most use; set to “Responsive” (+1) for small or erratic birds, or Case Manual with Accel./Decel. at +2 for dynamic flying birds

• Servo First Image Priority: Equal or Release Priority

• Minimum Shutter Speed: 1/2000s (to freeze motion)

If persistent focus lag is observed when birds leap into flight, users are advised to increase both Tracking Sensitivity and Accel./Decel. tracking up to +2. Conversely, for steadier, gliding subjects, more conservative values (-1, -2) are better to reduce jitter and prevent focus shifting if the subject briefly leaves the focus area.

Deep Learning Animal Subject Detection

One of the R5 Mark II’s most significant advancements is its improved deep learning-based subject recognition, especially for birds. The new system utilizes a much larger and more diverse training database, enhancing its ability to discriminate bird forms—even amid clutter, against complex backgrounds, or at extreme subject angles.

Bird eye detection, in particular, has matured and is now far more robust. Canon’s detection system can now lock on to birds’ eyes with higher reliability, even through partial obstructions like foliage or branches—a recurring difficulty with the Mark I and many competitor systems. With tracking tied to the detected eye, the system is less likely to “jump” to background objects or lose focus during rapid acceleration or deceleration; this is especially notable in burst sequences of small birds in complex settings, such as wood ducks moving quickly through reeds or waxwings darting inside dense cedars.

While users note that extreme cases—such as tiny, extremely fast birds (e.g., hummingbirds) or subjects in heavy visual clutter—can still challenge the system, success rates have increased markedly. Some field reviewers and photographers have even described the improved subject and eye detection as “knocking my socks off,” a testament to its dramatic gains over previous releases.

Practical Performance: Photographers’ Insights and User Feedback 

• Real-World Experience and Keeper Rates

Photographers report that the R5 Mark II produces average in-focus “keeper” rates exceeding 80–90% for birds in flight and maintains reliable tracking over long, dynamic sequences. One noted scenario involved capturing 90 consecutive frames of a duck taking off through intervening branches, each in perfect eye focus. This level of consistency, particularly in visually challenging scenes, represents a meaningful real-world benefit for bird and wildlife shooters.

Multiple users confirm that under “normal” flight (not extreme erratic movement at close range), the camera rarely loses focus once it is locked. For fast, head-on approach or birds rapidly changing speed, slight backfocus can occur in the very first frames post-acceleration, but the system corrections are swift—substantially better than the earlier R5 or even some competing industry-leading cameras.

• Performance With Small and Large Birds

Testimony from both casual and serious bird photographers converges around the R5 Mark II’s much improved performance on both large birds (e.g., eagles, ducks) and small, erratic subjects (e.g., hummingbirds). While ultimate tracking of extremely fast, random-movement birds at close range can still see occasional missed frames, most users find that increased “sticky” focus and improved subject reacquisition rate have made challenging shots feasible that were previously “luck and volume” situations.

• Limitations and User Strategies

Not every user is fully satisfied; some describe minor missed focus immediately after explosive take-offs or with highly camouflaged subjects in clutter. There is a consensus that optimal lens choice impacts maximum AF effectiveness: native RF lenses with the 12-pin connection facilitate faster, more precise data transfer and stabilization coordination, while older EF lenses, even top-tier supertelephotos, occasionally cannot match the highest tracking speeds due to slower communication lines and less precise response synergy.

Technical Reviews on Dynamic AF Performance

Major review outlets, including Digital Photography Review, TechRadar, PetaPixel, and Live Science, have all confirmed the R5 Mark II’s AF advancements as among the most substantial in Canon’s lineup. The AF engine, now boosted by a new back-illuminated stacked sensor and dual processing pipeline, is cited for both increased subject recognition intelligence and much reduced latency, especially through fast subject velocity changes.

Live Science underscores the “blackout-free” experience at 30 fps and lauds the reliability of the autofocus in both its acquisition and continuous tracking functions. TechRadar describes the AF as “near-perfect” and one of the most user-friendly and forgiving systems for professional action wildlife photography today, even if the newest Eye Control AF still needs refinement for universal accuracy.

Field testers at DPReview highlight the system’s “layered” approach—Servo AF at the foundation, deep learning subject recognition, and flexible override for manual tuning—allowing both automation for new users and sophisticated control for pros seeking to fine-tune tracking behavior per subject or per event.

Firmware Updates Affecting AF Performance

Canon’s commitment to continuous improvements is reflected in a steady cadence of firmware updates for the R5 Mark II. The latest version as of this report (v1.1.1, released July 2025) includes several direct and indirect AF enhancements:

• Improved AF tracking during video capture for difficult subjects

• Ability to select “Case Special” Servo AF characteristics (better for tracking through nets or obstacles)

• Improvements in image stabilization control and peripheral coordinated lens support

• Refinements in pre-capture and buffer management

While most firmware updates bring stability, bug fixes, and minor functional additions, users have reported that AF performance—particularly through challenging acceleration/deceleration scenarios—has been incrementally improved, especially for video shooting and complex environmental setups. Firmware updates also now support direct camera-to-internet updates, streamlining the acquisition of future improvements.

Comparison with Canon EOS R5 Mark I

The R5 Mark II’s autofocus system is more than an evolution of the R5’s already formidable offering; it represents a significant leap. The original R5 featured the first-generation Dual Pixel CMOS II system, with deep learning AF and animal detection introduced via firmware, but tracking was more susceptible to losing lock during abrupt movement or through complicated backgrounds.

Key improvements in the Mark II include:

• Stacked sensor for faster readout and less rolling shutter

• Dedicated dual processors (DIGIC X + Accelerator) for more sophisticated AF calculations

• Broader and smarter subject detection database

• Higher default burst rates (30 fps vs. 20 fps electronically) and blackout-free shooting

• Expanded and more intelligent customization of tracking and acceleration/deceleration parameters

• Pre-capture support (significant for unpredictable bird take-offs or “the missed moment”)

Comparative reviews and side-by-side field usage overwhelmingly confirm the R5 Mark II’s superiority in holding and reacquiring focus through challenging acceleration and deceleration, with the largest user-reported difference being in “keeper” rates and focus reliability when tracking small, fast-moving birds through clutter, or during rapid speed transitions. The Mark I, while still very capable, is sometimes prone to losing and seeking focus in these extreme scenarios. In sum, the new model is described as "stickier", faster, and much more reliable for action wildlife applications.

Comparison with Competitors (Sony A1 Mark II, Nikon Z9)

The professional mirrorless landscape is fiercely competitive; Sony’s Alpha A1 Mark II and Nikon’s Z9 are prime alternatives, both lauded for their powerful AF modules and deep learning recognition.

• Canon R5 Mark II vs. Sony A1 Mark II

Head-to-head analyses between the R5 Mark II and A1 II commonly find only minute differences in burst speed and “hit rates,” but key nuances emerge on closer scrutiny:

• Sony A1 II achieves slightly better “on-the-eye” lock-in for birds launching directly toward the camera, and initial “hit rates” for the first few frames after launch may be fractionally higher with certain settings.

• Canon R5 Mark II detects birds more readily and “sticks” to them more consistently across cluttered backgrounds or when the bird is partially occluded. The R5 Mark II is less prone to being distracted by high-contrast water highlights or background objects, an occasional issue reported with the Sony system.

• Customization and Responsiveness: Both systems allow nuanced tuning for tracking sensitivity and speed adaptation, but Canon’s implementation is often described as more intuitive and responsive for quick field changes.

Expert consensus on platform-centric forums and comparative video reviews suggest that for bird-in-flight scenarios involving rapid acceleration/deceleration and environmental challenge (branches, water, sky-to-forest transitions), the R5 Mark II may hold a subtle but meaningful advantage in reliability and user experience, especially with deep learning animal detection enabled. However, perfection in every scenario cannot be claimed by any system, and best performance often relies on user optimization of settings and choice of lens.

• Canon R5 Mark II vs. Nikon Z9

The Nikon Z9 also features rapid subject detection, AI-trained focus, and blackout-free operation at high burst rates, with most quantitative reviews equating the Nikon and Canon on keeper rates for straightforward bird-in-flight work. However, Canon’s superior animal eye detection and the fine-tuning capacity of its Flexible Zone AF and acceleration/deceleration settings—along with ever-maturing firmware—are considered slight, practical advantages for demanding wildlife professionals.

AF Performance Metrics: Tabular Summary

Metric	Canon R5 Mark II	Canon R5 Mark I	Sony A1 Mark II	Nikon Z9
Burst Rate (electronic)	30 fps (blackout-free)	20 fps	30 fps	20 fps (blackout-free)
AF Coverage	100% vert., 90% horiz. (manual); 100%x100% (auto)	100% x 90%	~100% x 100%	~90% x 90%
Deep Learning Detection	2nd-gen, greatly improved, larger database	1st-gen, refined by firmware	Latest, excellent	Latest, excellent
Accel./Decel. Tracking	Fully adjustable (-2 to +2) in Flexible Zone/case	Fixed cases, less nuanced	Fully customizable	Fully customizable
Autofocus Response to Sudden Speed	Locks and maintains focus with minimal lag	May lag or hunt in extreme	Slightly better initial	Comparable
Eye Detection (Birds)	Fast, robust, less susceptible to clutter	Good, less robust	Fast, sometimes distracted	Fast, robust
Pre-Capture Support	Yes (customizable): up to 1s before trigger	No	Yes	Yes
User Feedback (keeper rate for BIF)	80–95% in typical cases, up to 90+% in ideal	65–85%	85–95%	80–95%
Firmware Improvements	Frequent, AF algorithms refined continuously	Now stable	Stable, mature	Frequent, continuing development
Lens Stabilization Cooperation	Five-axis IBIS + RF lens IS; best with RF lenses	IBIS + lens IS; slower EF	IBIS + lens IS, strong	IBIS + lens IS, strong
Customization of Tracking Parameters	Deep, on-the-fly, AF-ON override possible	Less flexible	Equally deep	Deep customization
User Interface	Intuitive, improved layout, fast AF menu access	Good, less direct for some	Advanced, less intuitive	Advanced but complex
Forum/User Sentiment	Strongly positive, especially for wildlife/BIF	Mixed (good but with workarounds)	Strong positive	Strong positive

Despite the broad similarities at this high level of competition, the improvements in customization granularity, intelligent eye detection, and reliable zone autofocusing in the R5 Mark II are cited by many photographers as offering the most seamless real-world experience for BIF (birds in flight).

Pre-Capture and AF Tracking for Dynamic Subjects

An important enhancement in the R5 Mark II is robust support for pre-capture imaging: the camera can record frames up to 1 second before the shutter release, a feature invaluable for unpredictable take-offs or rapid acceleration events where human reaction lag often results in missed shots.

Practical reports suggest that while pre-capture mitigates reaction-time limitations, the efficacy of AF during these milliseconds is entirely dependent on tracking intelligence. Here, the camera maintains Servo AF calculations through the buffer, ensuring that even initial “pre-trigger” frames are subject to the latest focus predictions and subject detection algorithms. Reviewers note that when properly configured, pre-capture combined with responsive Flexible Zone AF nearly guarantees at least several, and often a majority, of in-focus frames even during the most sudden acceleration scenarios.

Lens Stabilization Impact on AF

Coordinated image stabilization (IBIS + lens IS) in the R5 Mark II is most effective with Canon’s RF series lenses, which utilize the new 12-pin mount for faster data exchange and decision synchronization between camera and lens. With RF telephotos (especially super-tele primes and high-quality zooms), stabilization is both broader (five axes) and more intelligently coordinated.

When using older EF glass, especially through adapters, IBIS and lens stabilization cooperate but may do so less efficiently, leading to a slight lag in focus correction under abrupt motion, or less stable tracking through camera shake. While the AF system in both cases remains very good, the sum performance when tracking rapidly accelerating or decelerating birds is at its highest with cutting-edge RF glass.

Autofocus Algorithm Research and Trends

Contemporary AF research, particularly in the field of deep learning and computer vision, validates the effectiveness of convolutional neural networks (CNNs) and real-time prediction algorithms for dynamic subject tracking. Wildlife-specific detection models—like those now powering Canon’s system—are trained on vast datasets of animal movement, producing feature detectors that are not only robust to occlusion and complex backgrounds, but also adaptive to subject speed variability.

This deep learning approach is further validated in published academic work and independent benchmarks, suggesting that real-time CNN-based object tracking, when combined with a rapid sensor and high-bandwidth processing pipeline, provides a tangible leap over traditional phase or contrast detect systems. Canon’s practical implementation of these insights in the R5 Mark II aligns closely with best-in-class algorithmic recommendations in recent literature.

Community and Forum Experiences

Analysis of community forums and online discussion boards reveals a highly positive sentiment around Canon R5 Mark II’s autofocus performance for high-difficulty dynamic wildlife. While not immune to criticism and still displaying occasional missteps (especially in the hardest, real-world BIF events), users commonly declare the AF system “a game changer,” with a markedly lower rate of missed focus due to sudden subject speed changes than on the original R5 and with stronger reliability compared to other systems in the field.

Conclusion: State-of-the-Art Acceleration and Deceleration AF for Birds in Flight

The Canon EOS R5 Mark II’s Flexible Zone AF system—backed by dual high-speed processors, a responsive stacked sensor, a robust deep-learning subject recognition database, and fine-grained user customization—sets a new industry benchmark for autofocus tracking of birds in flight, especially through phases of rapid acceleration and deceleration. In challenging, cluttered, or high-velocity scenarios, the R5 Mark II distinguishes itself with “sticky” focus, rapid reacquisition after speed changes, and a dramatic reduction in out-of-focus images. These improvements are most pronounced when using the latest RF lenses, and the system excels particularly when optimal tracking settings are selected for the subject at hand.

While some competitor systems may shade it in initial lock-on during the most direct launches and the most trivial of circumstances, Canon’s matured AF, elegant user controls, and ever-developing firmware result in an experience that is particularly well-aligned to the demands of bird and wildlife action photography. Incremental firmware updates, pre-capture, coordinated stabilization, and ongoing deep learning improvements suggest that the R5 Mark II’s capabilities are likely to continue growing over the coming update cycles.

In sum, the Canon EOS R5 Mark II Flexible Zone AF delivers industry-leading acceleration and deceleration subject tracking for birds in flight, and is, for many wildlife professionals and enthusiasts, the new standard by which fast action autofocus is measured." (Source: Microsoft Copilot)

Image: Canon USA