Pentax K-3 Mark IIIvs Sigma fp L

GearFrame · Updated March 2026

Pentax Pentax K-3 Mark III Pentax Pentax K-3 Mark III (2021) From £1699 Best for DSLR enthusiasts & outdoor photographers View Pentax K-3 Mark III
VS
Sigma Sigma fp L Sigma Sigma fp L (2021) From £1999 Best for High-resolution creative & documentary shooters View Sigma fp L

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.

High-Resolution Creative & Documentary Shooters — Sigma fp L (2021): 61MP and phase-detect AF in the world's smallest full-frame body — the fp L is the most capable iteration of Sigma's extraordinary compact.

↓ Full specifications below

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

Sigma fp L (2021)

  • You need the highest resolution available in the smallest possible full-frame mirrorless
  • You shoot architecture, landscape, or commercial work where fine detail is absolutely critical
  • You want the cinematic flexibility of the fp platform paired with maximum megapixel count

Quick take: The sigma fp l has the highest resolution at 61mp; the pentax k-3 mark iii is the most affordable; only the pentax k-3 mark iii is weather sealed. Scroll down for the full spec breakdown.

Full specifications

Specification Pentax K-3 Mark III (2021)Sigma fp L (2021)
Price £1,699 £1,999
Sensor 25.7MP APS-C BSI CMOS (AA-filterless) 61MP full-frame BSI CMOS
Resolution 25.7MP 61.0MP
Video 4K/30p, 1080p/60p 12-bit Cinema DNG RAW, 4K/24p
Autofocus SAFOX 13 phase-detect, 101-point (25 cross-type) Phase-detect AF with face/eye detection
Stabilisation 5.5-stop 5-axis IBIS (Shake Reduction III) None (lens-based only)
Burst Rate 12fps 18fps electronic
Battery Life 800 shots (CIPA) 200 shots (CIPA)
Weight 820g body only 427g body only
Dimensions 134.5 × 103.5 × 73.5mm 112.6 × 69.9 × 45.3mm
Weather Sealed Yes No
Viewfinder Optical pentaprism, 100% coverage, 1.05× magnification None (optional clip-on EVF available)
Screen 3.2" tilting touchscreen 3.15" fixed touchscreen
Mount Pentax KF-mount Leica L-mount
Memory Cards Dual SD UHS-II Single SD UHS-II
Connectivity USB-C, Wi-Fi, Bluetooth USB-C 3.1, Wi-Fi, Bluetooth
⚡ Compare specs side by side Pentax K-3 Mark III prices → Sigma fp L prices →

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