• Medium format 1,452.0mm2
  • 40.0 megapixels
  • ISO 200 - 1000
  • APS-C 355.7mm2
  • 14.2 megapixels
  • ISO 100 - 3200

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Differences

Pentax 645D advantages over Nikon D3100

  • Larger sensor
    Medium format vs APS-C
    More sensor area. Bigger is (generally) better.
  • Bigger pixels
    ~ 6.06 vs 5.01 microns
    Better low-light and dynamic range (all else equal)
  • Higher effective ISO
    1,262 vs 919 iso
    Take photos in low light with less noise
  • More dynamic range
    12.6 vs 11.2 evs
    Retain detail in highlight and shadows
  • Longer stills battery life
    More info 800 vs 550 shots
    Capture more photos
  • Top deck display
    Yes vs No
    Check settings with a screen on top of the camera
  • More cross-type AF points
    11 vs 1
    Cross-type AF points improve autofocus performance
  • More dots on screen
    921k vs 230k dots
    Can mean greater resolution or a brighter screen
  • Less shutter lag
    0.16 vs 0.28 sec
    Focus and take a photo quickly (wide angle)
  • More viewfinder magnification
    0.78x vs 0.53x
    Get a bigger view of the scene through the eye-level viewfinder
  • More pixels
    40.0 vs 14.2 megapixels
    Higher resolution photos
  • Dual card slots
    Yes vs No
    Gives you more storage flexibility
  • Lacks anti-aliasing filter
    No Filter vs Filter
    Enjoy sharper photos

Nikon D3100 advantages over Pentax 645D

  • Lens selection
    Excellent vs Limited
    Better lens selection gives you more options
  • Less expensive
    $700 vs $9996 (MSRP)
    Save money for lenses or accessories
  • Fast startup
    ~0.40 vs 0.7 sec
    Faster startup lets you catch the moment
  • Internal flash
    Internal flash vs None
    Useful in a pinch for fill flash
  • Thinner
    74 mm vs 119 mm
    Thinner
  • Higher max flash sync
    1/200 vs 1/125 sec
    Reduce the effect of ambient light in flash shots
  • Shoots 24p video
    Yes vs No
    Gives your movies a big-screen feel
  • Shoots 1080p video
    Yes vs No
    You'll want this if you shoot video
  • Has anti-aliasing filter
    Filter vs No Filter
    Reduces unsightly moiré in photos
  • Faster JPEG shooting
    2.9 fps vs 1.1 fps
    Faster JPEG shooting (burst mode)
  • Bigger JPEG buffer
    100 vs 19 shots
    Take more JPEG shots before waiting (burst mode)
  • Higher extended ISO
    12800 vs 1600 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
  • 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

  • Focus peaking
    Neither provide
    Your camera will highlight what's in focus
  • Tilt-swivel screen
    Neither provide
    Tilt and swivel the screen for maximum shooting flexibility
  • In-Camera Image Stabilization
    Neither provide
    Reduces the effects of camera shake at slower shutter speeds
  • Touchscreen
    Neither provide
    Interact with your camera just like your smartphone
  • In-camera panoramas
    Neither provide
    Stitches multiple shots into a panoramic photo
  • Tiltable Screen
    Neither provide
    Tilt the screen for shooting flexbility
  • 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
  • External Mic Jack
    Neither provide
    Improved sound fidelity when shooting video
  • Headphone jack
    Neither provide
    Monitor audio recording while you shoot video
  • Slow-motion videos
    Neither provide
    Shoot slow-motion videos

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Review Excerpt

  • Very high-resolution 40-megapixel sensor; Plentiful controls with great placement; Excellent optical viewfinder; Dual SDHC card slots; Infrared remote sensors front and back.

  • High price tag; Aliasing artifacts; Produces ~70MB RAW files.

The Competition

Compared to Sony DSLR-A380

Pentax 645D
Sony DSLR-A380
  • $3599
  • Medium format
  • Larger sensor
  • Bigger pixels
  • $849
  • APS-C
  • Lens selection
  • Less expensive
Nikon D3100
Sony DSLR-A380
  • $700
  • APS-C
  • Lens selection
  • Less expensive
  • $849
  • APS-C
  • In-Camera Image Stabilization
  • Tiltable Screen

Compared to Leica S2

Pentax 645D
Leica S2
  • $3599
  • Medium format
  • Less expensive
  • More cross-type AF points
  • $22995
  • Medium format
  • Thinner
  • More viewfinder magnification
Nikon D3100
Leica S2
  • $700
  • APS-C
  • Less expensive
  • Lens selection
  • $22995
  • Medium format
  • Larger sensor
  • Bigger pixels

Compared to Sony A33

Pentax 645D
Sony A33
  • $3599
  • Medium format
  • Larger sensor
  • Bigger pixels
  • $540
  • APS-C
  • Lens selection
  • Less expensive
Nikon D3100
Sony A33
  • $700
  • APS-C
  • Lens selection
  • Fast startup
  • $540
  • APS-C
  • In-Camera Image Stabilization
  • In-camera panoramas

Compared to Leica S (Typ 006)

Pentax 645D
Leica S (Typ 006)
  • $3599
  • Medium format
  • Less expensive
  • Higher effective ISO
  • $10535
  • Medium format
  • Thinner
  • More viewfinder magnification
Nikon D3100
Leica S (Typ 006)
  • $700
  • APS-C
  • Lens selection
  • Less expensive
  • $10535
  • Medium format
  • Larger sensor
  • Bigger pixels

Compared to Pentax 645Z

Pentax 645D
Pentax 645Z
  • $3599
  • Medium format
  • Fast startup
  • Longer stills battery life
  • $4845
  • Medium format
  • Focus peaking
  • Tiltable Screen
Nikon D3100
Pentax 645Z
  • $700
  • APS-C
  • Lens selection
  • Fast startup
  • $4845
  • Medium format
  • Focus peaking
  • Larger sensor
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