"Modern mirrorless cameras increasingly rely on electronic shutter systems alongside traditional mechanical shutters. These systems enable high-speed shooting, silent operation, and advanced buffer-based features like pre-capture or pre-continuous shooting. In both the Canon EOS R6 Mark III and EOS R5 Mark II, Canon extends this functionality to help photographers “catch the split second” in unpredictable action scenes. However, the sensor architecture, readout speed, and implementation details differ meaningfully between these two models, shaping how each camera’s shutter system behaves in real-world use (Canon Asia, 2025; Canon Rumors, 2025).
The R6 Mark III uses a front-illuminated CMOS sensor with a high-speed readout, while the R5 Mark II leverages a back-illuminated stacked CMOS sensor paired with Canon’s Accelerated Capture system. These differences affect how quickly each camera can read and buffer image data for pre-capture and continuous shooting modes (Canon Rumors, 2025; Snapshot Asia, 2025).
Pre-Capture / Pre-Continuous Shooting: Mechanism and Purpose
At the heart of this comparison is a feature now common to many high-end mirrorless bodies: pre-continuous shooting, sometimes called pre-capture. This function allows the camera to continuously buffer frames while the shutter button is half-pressed. Once the photographer fully depresses the shutter, the buffered frames from just before the actuation are saved alongside the new images. This is critical in sports, wildlife, and action photography, as it helps catch the precise moment that would otherwise be missed (Canon Asia, 2025; Digital Camera World, 2026).
For the R6 Mark III, pre-continuous shooting can buffer up to approximately 20 frames, or roughly half a second, before the shutter is fully pressed. Once a sequence is triggered, these frames are written to the memory card along with subsequent frames captured during the burst. This mode works only with the electronic shutter at high drive settings and requires an active continuous shooting mode (Canon Asia, 2025). Practically, this allows photographers to anticipate action — for example, a bird about to take flight — and capture the exact frames just before the shutter is pressed. The R6 Mark III supports this in RAW, C-RAW, JPEG, and HEIF formats, making pre-captured images immediately usable without additional processing.
The R5 Mark II features a similar pre-continuous shooting function, although its buffer captures up to 15 frames of pre-release data. Like the R6 Mark III, it requires the electronic shutter and continuous AF/AE tracking. Because the R5 Mark II’s sensor and readout architecture were designed for high-speed throughput, it efficiently manages pre-capture buffering while maintaining accurate autofocus and exposure evaluation. However, the buffer is slightly shorter than that of the R6 Mark III, reflecting sensor throughput limitations inherent in the earlier model (Canon Official, 2024; Snapshot Asia, 2025).
Electronic Shutter Performance and Rolling Shutter
The effectiveness of pre-continuous shooting depends on the electronic shutter’s ability to rapidly read and transfer sensor data. Here, the differences in sensor design between the R6 Mark III and R5 Mark II become significant.
The R5 Mark II employs a back-illuminated stacked CMOS sensor with a sensor readout time of around 6.3 milliseconds. This fast readout reduces rolling shutter distortion in electronic shutter mode, which is particularly important when photographing fast-moving subjects or using artificial lighting. The fast readout also allows the camera to maintain excellent image quality and, in some cases, support flash synchronization with the electronic shutter (Canon Rumors, 2025; Yahoo Tech, 2026).
In contrast, the R6 Mark III can reach up to 40 frames per second in continuous shooting mode using the electronic shutter, exceeding the R5 Mark II’s maximum of 30 fps. Although the R6 Mark III’s front-illuminated sensor has a slower readout than the R5 Mark II’s stacked sensor, Canon’s DIGIC X processor and buffer architecture make this high frame rate practical and stable. The increased fps also means more frames can be buffered for pre-capture and burst sequences. However, at the highest rates or under extreme panning conditions, rolling shutter artifacts may be more noticeable compared with the R5 Mark II (Canon Rumors, 2025; Yahoo Tech, 2026).
Mechanical vs. Electronic Shutter Behavior
Both cameras retain mechanical shutter and first-curtain electronic shutter modes, which influence tactile feedback and performance in mixed lighting or with flash. For pre-capture and high-speed burst shooting, both rely on the pure electronic shutter, as mechanical limits would otherwise constrain frame rates and buffer performance.
Mechanical shutter use remains important in certain situations, such as flash photography requiring guaranteed sync speeds, studio work where rolling shutter must be avoided, or for photographers who prefer the traditional shutter cadence. The R5 Mark II improves upon previous Canon models by enabling flash sync with the electronic shutter at certain frame rates, thanks to its stacked sensor. The R6 Mark III, while capable of silent and rapid shooting, does not extend the same level of electronic shutter flash support at the highest speeds (Canon Official, 2024; Digital Camera World, 2026).
Practical Shooting Implications
In fast-action scenarios such as birds in flight, athletes crossing finish lines, or motorsports, the pre-capture buffer is essential. The R6 Mark III’s 20-frame pre-capture buffer provides slightly more temporal coverage, ideal when timing is unpredictable. The R5 Mark II’s 15-frame buffer, while slightly shorter, benefits from the sensor’s fast readout, which reduces rolling shutter and distortion.
For workflow, both cameras deliver pre-captured frames in standard formats like RAW, C-RAW, JPEG, and HEIF. This means photographers can immediately import and process these images without extra extraction steps. The R6 Mark III, building on the R5 Mark II’s implementation, offers slightly larger temporal coverage, which may be useful in wildlife or sports photography where anticipation is challenging (Canon Asia, 2025; Tech Radar, 2026).
Summary Comparison of Shutter Performance
The R6 Mark III excels in maximum frame capture and pre-capture buffer length, enabling photographers to catch more lead-in frames in unpredictable action. Its electronic shutter allows up to 40 fps, and the 20-frame pre-capture buffer helps capture moments just before shutter actuation.
The R5 Mark II, with its stacked back-illuminated sensor, prioritizes electronic shutter quality, minimizing rolling shutter and supporting flash in electronic shutter mode at certain speeds. Its pre-capture buffer is slightly smaller at 15 frames, and its maximum electronic shutter frame rate is 30 fps.
For photographers, the choice between these bodies depends on whether extended frame coverage (R6 Mark III) or optimal electronic shutter quality and flash flexibility (R5 Mark II) is more critical to their shooting style and workflow. Both cameras provide highly effective pre-capture functionality, pushing the limits of what mirrorless systems can achieve for capturing fleeting moments." (Source: ChatGPT 2026)
References
Canon Asia. (2025). EOS R6 Mark III: The Power to Unleash Your Passion. Retrieved from https://snapshot.canon-asia.com/th/article/eng/eos-r6-mark-iii-the-power-to-unleash-your-passion?utm_source=chatgpt.com
Canon Official. (2024). Ultra Intelligent All-rounder: Canon Officially Launches EOS R5 Mark II. Retrieved from https://hk.canon/en/pro-imaging/eos-r5-mark-ii-sales-start/news?utm_source=chatgpt.com
Canon Rumors. (2025). Canon EOS R6 Mark III vs Canon EOS R5 Mark II. Retrieved from https://www.canonrumors.com/canon-eos-r6-mark-iii-vs-canon-r5-mark-ii/?utm_source=chatgpt.com
Digital Camera World. (2026). Canon EOS R5 vs EOS R6 Mark III: You might be surprised at which camera is better. Retrieved from https://www.digitalcameraworld.com/cameras/mirrorless-cameras/canon-eos-r5-vs-r6-mark-iii-you-might-be-surprised-at-which-camera-is-better?utm_source=chatgpt.com
Yahoo Tech. (2026). Canon EOS R6 III vs EOS R5 II: how much of a difference is there?. Retrieved from https://tech.yahoo.com/cameras/articles/canon-eos-r6-iii-vs-150000010.html?utm_source=chatgpt.com
Tech Radar. (2026). The Canon EOS R6 Mark III screams 'sensible upgrade' for pro hybrid shooters. Retrieved from https://www.techradar.com/cameras/mirrorless-cameras/the-canon-eos-r6-iii-screams-sensible-upgrade-for-pro-hybrid-shooters-and-that-should-worry-sony-and-nikon?utm_source=chatgpt.com
