• 35mm 861.6mm2
  • 24.6 megapixels
  • ISO 200 - 3200
  • APS-C 355.7mm2
  • 14.2 megapixels
  • ISO 100 - 3200

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Differences

Sony A900 advantages over Nikon D3100

  • Larger sensor
    35mm vs APS-C
    More sensor area. Bigger is (generally) better.
  • In-Camera Image Stabilization
    Yes vs No
    Reduces the effects of camera shake at slower shutter speeds
  • Bigger pixels
    ~ 5.94 vs 5.01 microns
    Better low-light and dynamic range (all else equal)
  • Higher effective ISO
    1,431 vs 919 iso
    Take photos in low light with less noise
  • Longer stills battery life
    More info 880 vs 550 shots
    Capture more photos
  • Top deck display
    Yes vs No
    Check settings with a screen on top of the camera
  • Pentaprism viewfinder
    Pentaprism vs Pentamirror
    Much better viewfinder picture fidelity
  • More dots on screen
    922k vs 230k dots
    Can mean greater resolution or a brighter screen
  • Less shutter lag
    0.18 vs 0.28 sec
    Focus and take a photo quickly (wide angle)
  • More viewfinder magnification
    0.74x vs 0.53x
    Get a bigger view of the scene through the eye-level viewfinder
  • More pixels
    24.6 vs 14.2 megapixels
    Higher resolution photos
  • Dual card slots
    Yes vs No
    Gives you more storage flexibility
  • Faster JPEG shooting
    5.0 fps vs 2.9 fps
    Faster JPEG shooting (burst mode)
  • Faster shutter
    1/8000 vs 1/4000 sec
    Shoot wide open in bright light

Nikon D3100 advantages over Sony A900

  • Less expensive
    $700 vs $3000 (MSRP)
    Save money for lenses or accessories
  • Lens selection
    Excellent vs Good
    Better lens selection gives you more options
  • Internal flash
    Internal flash vs None
    Useful in a pinch for fill flash
  • 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
  • Bigger JPEG buffer
    100 vs 11 shots
    Take more JPEG shots before waiting (burst mode)
  • Higher extended ISO
    12800 vs 6400 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
  • 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
  • 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

The Competition

Compared to Canon 5D Mark II

Sony A900
Canon 5D Mark II
  • $3000
  • 35mm
  • In-Camera Image Stabilization
  • More pixels
  • $2699
  • 35mm
  • Lens selection
  • Higher effective ISO
Nikon D3100
Canon 5D Mark II
  • $700
  • APS-C
  • Internal flash
  • Shoots 24p video
  • $2699
  • 35mm
  • Larger sensor
  • Bigger pixels

Compared to Sony A850

Sony A900
Sony A850
  • $3000
  • 35mm
  • Faster JPEG shooting
  • $2219
  • 35mm
  • Less expensive
  • Bigger JPEG buffer
Nikon D3100
Sony A850
  • $700
  • APS-C
  • Less expensive
  • Lens selection
  • $2219
  • 35mm
  • Larger sensor
  • In-Camera Image Stabilization

Compared to Sony A33

Sony A900
Sony A33
  • $3000
  • 35mm
  • Larger sensor
  • Bigger pixels
  • $540
  • APS-C
  • Less expensive
  • In-camera panoramas
Nikon D3100
Sony A33
  • $700
  • APS-C
  • Lens selection
  • Fast startup
  • $540
  • APS-C
  • In-Camera Image Stabilization
  • In-camera panoramas

Compared to Pentax K-r

Sony A900
Pentax K-r
  • $3000
  • 35mm
  • Larger sensor
  • Higher effective ISO
  • $850
  • APS-C
  • Lens selection
  • Less expensive
Nikon D3100
Pentax K-r
  • $700
  • APS-C
  • Less expensive
  • Higher effective ISO
  • $850
  • APS-C
  • In-Camera Image Stabilization
  • Fast startup

Compared to Canon 5D Mark III

Sony A900
Canon 5D Mark III
  • $3000
  • 35mm
  • In-Camera Image Stabilization
  • $2521
  • 35mm
  • Lens selection
  • Higher effective ISO
Nikon D3100
Canon 5D Mark III
  • $700
  • APS-C
  • Internal flash
  • Bigger JPEG buffer
  • $2521
  • 35mm
  • Larger sensor
  • Bigger pixels
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