• APS-C 372.9mm2
  • 12.3 megapixels
  • ISO 200 - 3200
  • 0.98 inch 285.7mm2
  • 4.7 megapixels
  • ISO 100 - 1600

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Differences

Nikon D90 advantages over Sigma SD15

  • Lens selection
    Excellent vs Limited
    Better lens selection gives you more options
  • Larger sensor
    APS-C vs 0.98 inch
    More sensor area. Bigger is (generally) better.
  • Longer stills battery life
    More info 850 vs 250 shots
    Capture more photos
  • HDMI out
    HDMI out vs None
    Use an external screen to monitor or review video
  • Shoots 24p video
    Yes vs No
    Gives your movies a big-screen feel
  • More dots on screen
    922k vs 460k dots
    Can mean greater resolution or a brighter screen
  • More viewfinder magnification
    0.63x vs 0.53x
    Get a bigger view of the scene through the eye-level viewfinder
  • More pixels
    12.3 vs 4.7 megapixels
    Higher resolution photos
  • More AF points
    11 vs 5
    More AF points improve autofocus
  • Faster JPEG shooting
    4.5 fps vs 3.0 fps
    Faster JPEG shooting (burst mode)
  • Bigger JPEG buffer
    Unlimited vs 21 shots
    Take more JPEG shots before waiting (burst mode)
  • Higher extended ISO
    6400 vs 3200 ISO
    Higher extended ISO can give more low-light flexibility

Sigma SD15 advantages over Nikon D90

  • Bigger pixels
    ~ 7.84 vs 5.50 microns
    Better low-light and dynamic range (all else equal)
  • Doesn't require an AA filter
    Yes vs No
    A unique sensor design provides sharp photos without moiré

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
  • Top deck display
    Both provide
    Check settings with a screen on top of the camera
  • Pentaprism viewfinder
    Both provide
    Much better viewfinder picture fidelity
  • 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
  • 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

User reviews

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Review Excerpt

The Competition

Compared to Sony DSLR-A300

Nikon D90
Sony DSLR-A300
  • $1300
  • APS-C
  • Lens selection
  • Higher effective ISO
  • $563
  • APS-C
  • Less expensive
  • In-Camera Image Stabilization
Sigma SD15
Sony DSLR-A300
  • $1000
  • 0.98 inch
  • Bigger pixels
  • Top deck display
  • $563
  • APS-C
  • Lens selection
  • Larger sensor

Compared to Sony DSLR-A330

Nikon D90
Sony DSLR-A330
  • $1300
  • APS-C
  • Lens selection
  • Fast startup
  • $530
  • APS-C
  • Less expensive
  • In-Camera Image Stabilization
Sigma SD15
Sony DSLR-A330
  • $1000
  • 0.98 inch
  • Bigger pixels
  • Top deck display
  • $530
  • APS-C
  • Lens selection
  • Larger sensor

Compared to Nikon D300S

Nikon D90
Nikon D300S
  • $1300
  • APS-C
  • Higher effective ISO
  • Bigger JPEG buffer
  • $1495
  • APS-C
  • External Mic Jack
  • More cross-type AF points
Sigma SD15
Nikon D300S
  • $1000
  • 0.98 inch
  • Less expensive
  • Bigger pixels
  • $1495
  • APS-C
  • Lens selection
  • Larger sensor

Compared to Sony DSLR-A550

Nikon D90
Sony DSLR-A550
  • $1300
  • APS-C
  • Lens selection
  • Fast startup
  • $859
  • APS-C
  • Less expensive
  • In-Camera Image Stabilization
Sigma SD15
Sony DSLR-A550
  • $1000
  • 0.98 inch
  • Bigger pixels
  • Top deck display
  • $859
  • APS-C
  • Lens selection
  • Larger sensor

Compared to Sony DSLR-A500

Nikon D90
Sony DSLR-A500
  • $1300
  • APS-C
  • Lens selection
  • Fast startup
  • $850
  • APS-C
  • Less expensive
  • In-Camera Image Stabilization
Sigma SD15
Sony DSLR-A500
  • $1000
  • 0.98 inch
  • Bigger pixels
  • Top deck display
  • $850
  • APS-C
  • Lens selection
  • Larger sensor
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