Pentax K-3 Mark IIIvs A7R III
Pentax
Pentax K-3 Mark III (2021)
Starting from £1699 new
Best for DSLR enthusiasts & outdoor photographers
View Pentax K-3 Mark III
Sony
A7R III (2017)
Starting from £1799 new
Best for Landscape, studio & commercial photography
View A7R III
GearScore™ Verdict — Which should you buy?
Dslr Enthusiasts & Outdoor Photographers — Pentax K-3 Mark III (2021): The finest APS-C DSLR ever made — class-leading weather sealing, optical viewfinder, 5-axis IBIS, and extraordinary build for photographers committed to DSLR.
Landscape, Studio & Commercial Photography — A7R III (2017): The camera that converted professionals to mirrorless — 42MP, IBIS, and 10fps in a body that still competes today.
Who should buy what
Pentax K-3 Mark III (2021)
- DSLR photographers who want the finest APS-C optical viewfinder experience
- Outdoor and weather photographers who need robust all-weather sealing
- Pentax lens owners who want to use their existing K-mount glass
- Photographers who prefer optical viewfinders and refuse to switch to mirrorless
A7R III (2017)
- Landscape and studio photographers who need 42MP resolution at a used-price discount vs A7R IV
- Canon/Nikon DSLR professionals considering a mirrorless switch at a lower investment
- Commercial and product photographers who want full-frame resolution with IBIS for handheld work
- Portrait photographers who want the sharpest possible full-frame files for large print work
Quick take: The a7r iii has the highest resolution at 42mp; the pentax k-3 mark iii is the most affordable. Scroll down for the full spec breakdown.
Full specifications
| Specification | Pentax K-3 Mark III (2021) | A7R III (2017) |
|---|---|---|
| Price | £1,699 | £1,799 |
| Sensor | 25.7MP APS-C BSI CMOS (AA-filterless) | 42.4MP full-frame BSI Exmor R CMOS |
| Resolution | 25.7MP | 42.4MP |
| Video | 4K/30p, 1080p/60p | 4K/30p (full-frame readout), 1080p/120p |
| Autofocus | SAFOX 13 phase-detect, 101-point (25 cross-type) | 399 phase-detect + 425 contrast AF points — real-time Eye AF |
| Stabilisation | 5.5-stop 5-axis IBIS (Shake Reduction III) | 5-axis IBIS — 5.5 stops |
| Burst Rate | 12fps | 10fps with AF/AE tracking |
| Battery Life | 800 shots (CIPA) | ~650 shots (CIPA) |
| Weight | 820g body only | 650g body only |
| Dimensions | 134.5 × 103.5 × 73.5mm | 126.9 × 95.6 × 73.7mm |
| Weather Sealed | Yes | Yes |
| Viewfinder | Optical pentaprism, 100% coverage, 1.05× magnification | EVF, 3.69M dots, 0.78× magnification |
| Screen | 3.2" tilting touchscreen | 3.0" touchscreen, tilting |
| Mount | Pentax KF-mount | Sony FE mount (full-frame E-mount) |
| Memory Cards | Dual SD UHS-II | Dual SD slots (one UHS-II) |
| Connectivity | USB-C, Wi-Fi, Bluetooth | USB-C, Bluetooth, Wi-Fi, 3.5mm mic jack |
Suitability by genre
| Genre | Pentax K-3 Mark III | A7R III |
|---|---|---|
| Landscape | ||
| Wildlife | — | |
| Sports & Action | — | |
| Portrait | ||
| Travel | — | |
| Vlogging & Video | ||
| Wedding | — | |
| Street | — | |
| Sports | — |
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