Sony A7 III vs Canon 5D Mark IV: Which Full-Frame Refurbished Should You Buy?

The Sony A7 III and Canon 5D Mark IV represent two fundamentally different approaches to full-frame photography. The Sony A7 III, released in 2018, is a mirrorless camera built around speed, autofocus performance, and modern technology. The Canon 5D Mark IV, released in 2016, is a DSLR that prioritises ergonomics, optical viewfinder experience, and proven reliability. Both are now firmly in the £700–£1,000 used market, making them two of the most compelling full-frame options for UK buyers in 2026.

This comparison examines the key differences across autofocus, image quality, video, ergonomics, battery life, and lens ecosystems — and provides a clear decision framework for which camera suits your specific needs.

Specs Comparison at a Glance

Autofocus: Sony's Clear Advantage

The Sony A7 III uses Sony's Fast Hybrid AF system with 693 phase-detect points covering 93% of the frame. The Canon 5D Mark IV has 61 phase-detect points plus Dual Pixel CMOS AF for live view and video. In real-world use, the Sony's AF is significantly faster to lock, more reliable in low light, and substantially better at tracking moving subjects.

For portrait, wildlife, event, and video work, the Sony's autofocus advantage is material and you will notice it every session. The Canon's AF is perfectly adequate for static subjects and controlled studio work, but it trails the Sony in continuous tracking scenarios.

Verdict: Sony A7 III wins decisively on autofocus.

Image Quality: Effectively Equivalent

Both cameras produce outstanding image quality. The Canon has a higher resolution sensor (30.4MP vs 24.2MP), which gives it an advantage for landscape and studio work where maximum detail matters. The Sony's sensor offers slightly better dynamic range and cleaner high-ISO performance.

The Canon's colour science is widely praised for producing warm, flattering skin tones straight out of camera — a characteristic that has made Canon the preferred choice of portrait and wedding photographers. Sony's files are more neutral and technically accurate, rewarding post-processing but requiring more work to achieve warm, natural-looking skin tones.

Verdict: Draw — Canon wins on resolution and colour science, Sony wins on dynamic range and high-ISO.

Video: Canon's Dual Pixel Advantage

The Canon 5D Mark IV's Dual Pixel CMOS AF is exceptional for video. It provides smooth, reliable continuous autofocus that is genuinely useful for hybrid photographers and content creators. The Sony A7 III's video AF is competent but noticeably slower and less predictable, particularly when tracking moving subjects.

However, the Canon shoots 4K with a 1.74x crop, which is a significant limitation for wide-angle video work. The Sony shoots 4K without crop. For serious video work, the Canon's AF advantage is offset by its 4K crop limitation.

Verdict: Canon wins on video autofocus, Sony wins on 4K framing.

Ergonomics: Canon's Optical Viewfinder

The Canon 5D Mark IV is significantly larger and heavier (890g vs 565g) with a deeper grip that many photographers find more comfortable for extended shooting. Its optical viewfinder shows the world directly with zero lag and no battery consumption — a characteristic that many photographers find preferable to electronic viewfinders, even excellent ones.

The Sony A7 III is considerably more compact and lighter, with an electronic viewfinder that is excellent but does introduce a small amount of lag and consumes battery power. For travel and run-and-gun shooting, the Sony's size and weight are significant advantages.

Verdict: Canon wins on ergonomics and optical viewfinder experience, Sony wins on portability.

Battery Life: Canon Wins Significantly

The Canon 5D Mark IV is rated at approximately 900 shots per charge (CIPA). The Sony A7 III manages approximately 610 shots per charge. For photographers who shoot in the field without easy access to charging, this difference is meaningful.

Verdict: Canon 5D Mark IV wins decisively on battery life.

Lens Ecosystems

The Canon EF mount has been in production since 1987 and supports decades of accumulated lenses. The used market for Canon EF glass is extensive and affordable. The Sony E-mount is newer (2010) but has grown dramatically and now has the largest native mirrorless lens ecosystem of any manufacturer.

For buyers starting from scratch, Sony's E-mount offers more modern lenses and better third-party support. For existing Canon users, the EF mount offers unmatched depth of used glass at low prices.

Verdict: Sony wins for new buyers, Canon wins for existing EF-mount users.

Who Should Buy Which?

Our Verdict

For most photographers buying into a full-frame system from scratch, the Sony A7 III is the stronger all-round choice — its autofocus advantage is real and meaningful across a wide range of shooting scenarios, its compact size is a genuine practical benefit, and its modern lens ecosystem offers more flexibility.

The Canon 5D Mark IV is the right choice for photographers who prioritise optical viewfinder experience, need exceptional battery life, or already own Canon EF-mount glass. For pure stills photography, the Canon's ergonomics and colour science remain compelling differentiators.

Both cameras represent exceptional value at their current used market prices. Either will serve you well for years of serious photography.