EOS R100vs Pentax K-3 Mark IIIvs A7S III
Pentax
Pentax K-3 Mark III (2021)
From £1699
Best for DSLR enthusiasts & outdoor photographers
View Pentax K-3 Mark III
Which should you buy?
First Camera / Beginner Photography — EOS R100 (2023): The R100 does the basics well at the lowest possible price point. Its main value is as a gateway into the Canon RF ecosystem — the lenses you buy now will work on any Canon body you upgrade to later. Modest ambitions, reliably met.
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.
Professional Video & Low-Light Filmmaking — A7S III (2020): If video is your primary discipline, the A7S III is the camera. 4K/120p at 10-bit in a weather-sealed body with a 9.44M dot EVF is an extraordinary package. The 12MP sensor isn't limiting for video — and it's usable at ISO 409,600 in a pinch.
Who should buy what
EOS R100 (2023)
- First-time camera buyers stepping up from a smartphone
- Students and hobbyists wanting an affordable starting point
- Anyone who wants to start investing in Canon RF glass on a budget
- Casual photographers who don't need advanced video or speed
Pentax K-3 Mark III (2021)
- You're a committed DSLR photographer with significant investment in Pentax glass
- You shoot in extreme weather conditions and place build quality and reliability above everything
- You prefer optical viewfinder performance and want the best modern APS-C DSLR available
A7S III (2020)
- Filmmakers and videographers who need 4K/120p at 10-bit
- Event videographers who shoot in dark venues regularly
- Documentary filmmakers who need reliable AF and weather sealing
- Hybrid shooters where video is primary and stills are secondary
Quick take: The pentax k-3 mark iii has the highest resolution at 26mp; the eos r100 is the most affordable; only the pentax k-3 mark iii, a7s iii are weather sealed. Scroll down for the full spec breakdown.
Full specifications
| Specification | EOS R100 (2023) | Pentax K-3 Mark III (2021) | A7S III (2020) |
|---|---|---|---|
| Price | £529 | £1,699 | £2,999 |
| Sensor | 24.1MP APS-C CMOS | 25.7MP APS-C BSI CMOS (AA-filterless) | 12.1MP Full-Frame BSI CMOS (12-bit, back-illuminated) |
| Resolution | 24.1MP | 25.7MP | 12.1MP |
| Video | 4K/30p (slight crop), 1080p/60p | 4K/30p, 1080p/60p | 4K/120p 10-bit, 4K/60p 10-bit S-Cinetone/S-Log3, 1080p/240p |
| Autofocus | Dual Pixel CMOS AF, face detection, subject tracking | SAFOX 13 phase-detect, 101-point (25 cross-type) | Phase-detect, 759 points, real-time Eye AF (human & animal), subject recognition |
| Stabilisation | None (no IBIS) | 5.5-stop 5-axis IBIS (Shake Reduction III) | 5.5-stop IBIS |
| Burst Rate | 6.5fps mechanical | 12fps | 10fps mechanical |
| Battery Life | ~270 shots (CIPA) | 800 shots (CIPA) | ~600 shots (CIPA) / ~70min continuous 4K recording |
| Weight | 356g (body, battery, card) | 820g body only | 699g (body, battery, card) |
| Dimensions | 116.3 × 85.5 × 68.8mm | 134.5 × 103.5 × 73.5mm | 128.9 × 96.9 × 80.8mm |
| Weather Sealed | No | Yes | Yes |
| Viewfinder | EVF, 2.36M dots, 0.59× magnification | Optical pentaprism, 100% coverage, 1.05× magnification | OLED EVF, 9.44M dots, 0.90× magnification — best EVF Sony has made |
| Screen | 3.0" fixed touchscreen, 1.04M dots | 3.2" tilting touchscreen | 3.0" vari-angle touchscreen, 1.44M dots |
| Mount | Canon RF-mount | Pentax KF-mount | Sony E-mount |
| Memory Cards | Single SD UHS-II | Dual SD UHS-II | Dual CFexpress Type A / SD UHS-II (both slots) |
| Connectivity | USB-C, Wi-Fi, Bluetooth | USB-C, Wi-Fi, Bluetooth | USB-C (USB 3.2 Gen 2), full-size HDMI, Wi-Fi 6, Bluetooth |
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