• APS-C 369.7mm2
  • 12.4 megapixels
  • ISO 200 - 6400
  • APS-C 368.2mm2
  • 16.2 megapixels
  • ISO 100 - 6400

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Differences

Pentax K-x advantages over Nikon D5100

  • Less expensive
    $650 vs $900 (MSRP)
    Save money for lenses or accessories
  • In-Camera Image Stabilization
    Yes vs No
    Reduces the effects of camera shake at slower shutter speeds
  • Bigger pixels
    ~ 5.53 vs 4.79 microns
    Better low-light and dynamic range (all else equal)
  • More cross-type AF points
    9 vs 1
    Cross-type AF points improve autofocus performance
  • Less shutter lag
    0.10 vs 0.27 sec
    Focus and take a photo quickly (wide angle)
  • More viewfinder magnification
    0.57x vs 0.52x
    Get a bigger view of the scene through the eye-level viewfinder
  • Faster shutter
    1/6000 vs 1/4000 sec
    Shoot wide open in bright light

Nikon D5100 advantages over Pentax K-x

  • Tilt-swivel screen
    Tilt-swivel vs none
    Tilt and swivel the screen for maximum shooting flexibility
  • Higher effective ISO
    1,183 vs 811 iso
    Take photos in low light with less noise
  • Longer stills battery life
    More info 660 vs 420 shots
    Capture more photos
  • External Mic Jack
    Jack vs No jack
    Improved sound fidelity when shooting video
  • HDMI out
    HDMI out vs None
    Use HDMI output to monitor or review video
  • More dots on screen
    922k vs 230k dots
    Can mean greater resolution or a brighter screen
  • Shoots 1080p video
    Yes vs No
    You'll want this if you shoot video
  • More pixels
    16.2 vs 12.4 megapixels
    Higher resolution photos
  • Bigger JPEG buffer
    100 vs 25 shots
    Take more JPEG shots before waiting (burst mode)
  • Higher extended ISO
    25600 vs 12800 ISO
    Higher extended ISO can give more low-light flexibility

Similarities

Common Strengths

  • Eye-level viewfinder
    Both provide
    You'll be able to frame photos even when the sun is out
  • Internal flash
    Both provide
    Useful in a pinch for fill flash
  • Hot shoe
    Both provide
    Off-camera flashes open new possibilities
  • Bulb shutter
    Both provide
    Hold the shutter open manually for long exposures

Common Weaknesses

  • Focus peaking
    Neither provide
    Your camera will highlight what's in focus
  • Touchscreen
    Neither provide
    Interact with your camera just like your smartphone
  • In-camera panoramas
    Neither provide
    Stitches multiple shots into a panoramic photo
  • Built-in Wi-Fi
    Neither provide
    Share your photos wirelessly
  • 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
  • On-sensor phase detect
    Neither provide
    Usually improves live view and video AF performance
  • Top deck display
    Neither provide
    Check settings with a screen on top of the camera
  • Pentaprism viewfinder
    Neither provide
    Much better viewfinder picture fidelity
  • Dual card slots
    Neither provide
    Gives you more storage flexibility
  • Headphone jack
    Neither provide
    Monitor audio recording while you shoot video
  • Slow-motion videos
    Neither provide
    Shoot slow-motion videos

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Buy the Nikon D5100

Review Excerpt

  • Side-mounted tilt / swivel LCD screen; same sensor and processing as the Nikon D7000; good speed and battery life; in-camera HDR and filter effects; Full HD video capture with aperture control; audio levels control and external microphone jack.

  • AF-S lens mount doesn't offer autofocus with screw-drive lenses; popup flash isn't the greatest; no built-in wireless flash control; HDR function doesn't microalign source images.

The Competition

Compared to Sony DSLR-A380

Pentax K-x
Sony DSLR-A380
  • $702
  • APS-C
  • Lens selection
  • Less expensive
  • $849
  • APS-C
  • Tiltable Screen
  • HDMI out
Nikon D5100
Sony DSLR-A380
  • $650
  • APS-C
  • Lens selection
  • Tilt-swivel screen
  • $849
  • APS-C
  • In-Camera Image Stabilization
  • Bigger JPEG buffer

Compared to Pentax K-7

Pentax K-x
Pentax K-7
  • $702
  • APS-C
  • Less expensive
  • Higher effective ISO
  • $1300
  • APS-C
  • Longer stills battery life
  • Top deck display
Nikon D5100
Pentax K-7
  • $650
  • APS-C
  • Less expensive
  • Tilt-swivel screen
  • $1300
  • APS-C
  • In-Camera Image Stabilization
  • Top deck display

Compared to Sony A55

Pentax K-x
Sony A55
  • $702
  • APS-C
  • Lens selection
  • Less expensive
  • $734
  • APS-C
  • In-camera panoramas
  • Tiltable Screen
Nikon D5100
Sony A55
  • $650
  • APS-C
  • Lens selection
  • Tilt-swivel screen
  • $734
  • APS-C
  • In-Camera Image Stabilization
  • In-camera panoramas

Compared to Pentax K-r

Pentax K-x
Pentax K-r
  • $702
  • APS-C
  • Less expensive
  • Shoots 24p video
  • $850
  • APS-C
  • Fast startup
  • External Mic Jack
Nikon D5100
Pentax K-r
  • $650
  • APS-C
  • Tilt-swivel screen
  • Higher effective ISO
  • $850
  • APS-C
  • In-Camera Image Stabilization
  • Bigger pixels

Compared to Sony A57

Pentax K-x
Sony A57
  • $702
  • APS-C
  • Lens selection
  • Less expensive
  • $800
  • APS-C
  • Focus peaking
  • In-camera panoramas
Nikon D5100
Sony A57
  • $650
  • APS-C
  • Lens selection
  • Tilt-swivel screen
  • $800
  • APS-C
  • Focus peaking
  • In-Camera Image Stabilization
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