• APS-C 366.6mm2
  • 20.1 megapixels
  • ISO 100 - 51,200
  • 4/3 226.2mm2
  • 20.4 megapixels
  • ISO 200 - 25,600

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Differences

Pentax K-S1 advantages over Olympus E-M1 Mark III

  • Larger sensor
    APS-C vs 4/3
    More sensor area. Bigger is (generally) better.
  • Bigger pixels
    ~ 4.29 vs 3.36 microns
    Better low-light and dynamic range (all else equal)
  • Internal flash
    Internal flash vs None
    Useful in a pinch for fill flash
  • Optional anti-aliasing filter
    Optional vs None
    Lets you choose sharper photos or reduced moiré
  • Higher extended ISO
    51200 vs 25600 ISO
    Higher extended ISO can give more low-light flexibility

Olympus E-M1 Mark III advantages over Pentax K-S1

  • Tilt-swivel screen
    Tilt-swivel vs none
    Tilt and swivel the screen for maximum shooting flexibility
  • Shoot 4K video
    4K (DCI) vs 1080p
    Make sure you have a fast computer
  • Touchscreen
    Touch vs No touch
    Interact with your camera just like your smartphone
  • High resolution composite
    Yes vs No
    Combine multiple shots to form a super hi-res version
  • Built-in Wi-Fi
    Wi-Fi vs None
    Share your photos wirelessly
  • On-sensor phase detect
    Yes vs No
    Usually improves live view and video AF performance
  • External Mic Jack
    Jack vs No jack
    Improved sound fidelity when shooting video
  • Newer
    5 years vs 10 years old
    Newer cameras often support more advanced features
  • Dual card slots
    Yes vs No
    Gives you more storage flexibility
  • Headphone jack
    Yes vs No
    Monitor audio recording while you shoot video
  • Longer exposure
    60 vs 30 sec
    Long exposures for night shots
  • Faster shutter
    1/32000 vs 1/6000 sec
    Shoot wide open in bright light

Similarities

Common Strengths

  • Focus peaking
    Both provide
    Your camera will highlight what's in focus
  • Eye-level viewfinder
    Both provide
    You'll be able to frame photos even when the sun is out
  • In-Camera Image Stabilization
    Both provide
    Reduces the effects of camera shake at slower shutter speeds
  • HDMI out
    Both provide
    Use HDMI output to monitor or review video
  • Hot shoe
    Both provide
    Off-camera flashes open new possibilities
  • Bulb shutter
    Both provide
    Hold the shutter open manually for long exposures

Common Weaknesses

  • In-camera panoramas
    Neither provide
    Stitches multiple shots into a panoramic photo
  • NFC
    Neither provide
    Simplifies pairing your camera with supported phones
  • Built-in Bluetooth
    Neither provide
    Always-on wireless connectivity
  • Built-in GPS
    Neither provide
    Geotag your photos
  • Top deck display
    Neither provide
    Check settings with a screen on top of the camera
  • Slow-motion videos
    Neither provide
    Shoot slow-motion videos

User reviews

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Buy the Pentax K-S1
Body Only
  • Body Only
  • Kit with 18-55mm and 50-200mm Lenses
All K-S1 Deals

Your purchases support this site

Buy the Olympus E-M1 Mark III
Body Only
  • Body Only
  • Kit with 12-100mm f/4 Lens
  • Kit with 12-40mm Lens
All E-M1 Mark III Deals

Review Excerpt

The Competition

Compared to Sony A58

Pentax K-S1
Sony A58
  • $502
  • APS-C
  • Lens selection
  • Higher effective ISO
  • $598
  • APS-C
  • Less expensive
  • In-camera panoramas

Compare Pentax K-S1 vs Sony A58

Olympus E-M1 Mark III
Sony A58
  • $1649
  • 4/3
  • Lens selection
  • Tilt-swivel screen
  • $598
  • APS-C
  • Larger sensor
  • Bigger pixels

Compare Olympus E-M1 Mark III vs Sony A58

Compared to Nikon D5500

Pentax K-S1
Nikon D5500
  • $502
  • APS-C
  • Focus peaking
  • In-Camera Image Stabilization
  • $697
  • APS-C
  • Tilt-swivel screen
  • Touchscreen

Compare Pentax K-S1 vs Nikon D5500

Olympus E-M1 Mark III
Nikon D5500
  • $1649
  • 4/3
  • Focus peaking
  • In-Camera Image Stabilization
  • $697
  • APS-C
  • Less expensive
  • Larger sensor

Compare Olympus E-M1 Mark III vs Nikon D5500

Compared to Pentax K-S2

Pentax K-S1
Pentax K-S2
  • $502
  • APS-C
  • Higher-res screen
  • $499
  • APS-C
  • Tilt-swivel screen
  • Built-in Wi-Fi

Compare Pentax K-S1 vs Pentax K-S2

Olympus E-M1 Mark III
Pentax K-S2
  • $1649
  • 4/3
  • Shoot 4K video
  • Touchscreen
  • $499
  • APS-C
  • Larger sensor
  • Bigger pixels

Compare Olympus E-M1 Mark III vs Pentax K-S2

Compared to Panasonic G95

Pentax K-S1
Panasonic G95
  • $502
  • APS-C
  • Larger sensor
  • Bigger pixels
  • $848
  • 4/3
  • Tilt-swivel screen
  • Shoot 4K video

Compare Pentax K-S1 vs Panasonic G95

Olympus E-M1 Mark III
Panasonic G95
  • $1649
  • 4/3
  • High resolution composite
  • On-sensor phase detect
  • $848
  • 4/3
  • Less expensive
  • In-camera panoramas

Compare Olympus E-M1 Mark III vs Panasonic G95

Compared to OM System OM-1

Pentax K-S1
OM System OM-1
  • $502
  • APS-C
  • Less expensive
  • Larger sensor
  • $2200
  • 4/3
  • Tilt-swivel screen
  • Shoot 4K video

Compare Pentax K-S1 vs OM System OM-1

Olympus E-M1 Mark III
OM System OM-1
  • $1649
  • 4/3
  • $2200
  • 4/3
  • Newer
  • Higher-res screen

Compare Olympus E-M1 Mark III vs OM System OM-1

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