EOS R100vs A7 IVvs A7S 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.
Portrait & Wedding Photography — A7 IV (2021): The full-frame portrait benchmark — 33MP, AI Eye AF, and exceptional skin-tone rendering in a pro-grade hybrid body.
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
A7 IV (2021)
- You want a high-resolution full-frame all-rounder for portraits, weddings, or travel
- You're stepping up from APS-C or a DSLR and want the best all-round full-frame body under £3,000
- You shoot a mix of stills and video and need a single body that handles both seriously
- You want access to the widest lens ecosystem in the mirrorless market
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 a7 iv has the highest resolution at 33mp; the eos r100 is the most affordable; only the a7 iv, a7s iii are weather sealed. Scroll down for the full spec breakdown.
Full specifications
| Specification | EOS R100 (2023) | A7 IV (2021) | A7S III (2020) |
|---|---|---|---|
| Price | £529 | £2,299 | £2,999 |
| Sensor | 24.1MP APS-C CMOS | 33MP Full-frame BSI Exmor R CMOS | 12.1MP Full-Frame BSI CMOS (12-bit, back-illuminated) |
| Resolution | 24.1MP | 33.0MP | 12.1MP |
| Video | 4K/30p (slight crop), 1080p/60p | 4K/60p oversampled, 10-bit internal, S-Log3, S-Cinetone | 4K/120p 10-bit, 4K/60p 10-bit S-Cinetone/S-Log3, 1080p/240p |
| Autofocus | Dual Pixel CMOS AF, face detection, subject tracking | 759-point phase-detect, AI subject recognition | Phase-detect, 759 points, real-time Eye AF (human & animal), subject recognition |
| Stabilisation | None (no IBIS) | 5-axis IBIS, 5.5 stops | 5.5-stop IBIS |
| Burst Rate | 6.5fps mechanical | 10fps mechanical, 30fps electronic | 10fps mechanical |
| Battery Life | ~270 shots (CIPA) | ~580 shots (CIPA) | ~600 shots (CIPA) / ~70min continuous 4K recording |
| Weight | 356g (body, battery, card) | 659g body only | 699g (body, battery, card) |
| Dimensions | 116.3 × 85.5 × 68.8mm | 131.3 × 96.4 × 79.8mm | 128.9 × 96.9 × 80.8mm |
| Weather Sealed | No | Yes | Yes |
| Viewfinder | EVF, 2.36M dots, 0.59× magnification | EVF, 3.69M dots, 0.78× magnification | OLED EVF, 9.44M dots, 0.90× magnification — best EVF Sony has made |
| Screen | 3.0" fixed touchscreen, 1.04M dots | 3.0" vari-angle touchscreen | 3.0" vari-angle touchscreen, 1.44M dots |
| Mount | Canon RF-mount | Sony FE (full-frame E-mount) | Sony E-mount |
| Memory Cards | Single SD UHS-II | Dual slots: CFexpress Type A + SD UHS-II | Dual CFexpress Type A / SD UHS-II (both slots) |
| Connectivity | USB-C, Wi-Fi, Bluetooth | USB-C (3.2 Gen 2), Bluetooth, Wi-Fi | USB-C (USB 3.2 Gen 2), full-size HDMI, Wi-Fi 6, Bluetooth |
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