BlackBerry's back: Z10 camera review
DxOMark Mobile Report: Blackberry Z10
With a DxOMark Mobile score of 67 the Blackberry Z10 is ranked toward the lower end of the DxO smartphone ranking. Its score is one point above the HTC 8X and Nokia Lumia 920 Windows phones, but it cannot keep up with the best in class such as the Nokia 808, Apple iPhone 5 or Samsung Galaxy S3.
The DxOMark team report that the Blackberry Z10 captures images with "Nice detail preservation including in low light conditions," "good white balance," overall good auto exposure" and "accurate autofocus in most situations."
On the downside: Images show "very strong luminance noise in low light," "clearly visible color shading with tungsten light source in low light or D50 lighting" and "slight color fringing. When using the flash, white balance can be inaccurate." Color shading occurs when flash is mixed with a tungsten light source.
In video mode, DxOMark's engineers reported that the Blackberry Z10 offers "reactive autofocus with some tracking abilities," but on the downside video footage shows "visible color non-uniformities," "perfectible texture reproduction" and provides "inefficient video stabilization."
Color, Exposure and Contrast
The DxOMark team found that the Blackberry Z10's images show "overall good auto exposure," "nice and pleasant colors outdoors" and "good white balance." However, the Blackberry tends to underexpose in low light and shows "slight color shading with tungsten light source in low light or D50 lightings." Because of this DxOMark scored the Blackberry Z10 at 81/100 for color in bright light and 65/100 in low light.
Overall DxOMark awarded the Blackberry Z10 scores of:
- 4.2 out of 5 for Exposure
- 4.0 out of 5 for White Balance accuracy
- 3.0 out of 5 for Color shading in low light*
- 3.5 out of 5 for Color shading in bright light*
- 3.0 out of 5 for Color Rendering in low light
- 4.5 out of 5 for Color Rendering in bright light
*Color Shading is the nasty habit cellphone cameras have of rendering different areas of the frame with different color shifts, resulting in pictures with, for example, pinkish centers and greenish corners.
Noise and Details
DxOMark's engineers reported that the Blackberry Z10 image output shows "nice detail preservation including in low light conditions." On the other hand luminance noise is "very strong in low light conditions."
Texture Acutance is a way of measuring the ability of a camera to capture images that preserve fine details, particularly the kind of low contrast detail (textures such as fine foliage, hair, fur) that can be blurred away by noise reduction or obliterated by excessive sharpening.
Sharpness is an important part of the quality of an image, but while it is easy to look at an image and decide visually whether it's sharp or not, the objective measurement of sharpness is less straightforward.
An image can be defined as "sharp" if its edges are sharp and if fine details are visible, but in-camera processing means it's possible to have one of these (sharp edges) but not the other (fine details). Conventional MTF measurements tell us how sharp an edge is, but have drawbacks when it comes to measuring fine detail preservation. Image processing algorithms can detect edges and enhance their sharpness, but they can also find homogeneous areas and smooth them out to reduce noise.
Texture Acutance, on the other hand, can qualify sharpness in terms of preservation of fine details, without being fooled by edge enhancement algorithms.
At first sight, the images from these two cameras may appear equally sharp. A sharpness measurement on edges will indeed confirm this impression, and will even show that the second camera is sharper. But a closer examination of low contrasted textures shows that the first camera has a better preservation of fine details than the second. The purpose of the Texture Acutance measurement is to qualify this difference.
Visual Noise is a value designed to assess the noise in an image as perceived by the human visual system, depending on the viewing condition (size of image, size of screen or print, viewing distance). The measurements have no units and can be simply viewed as a weighted average of noise standard deviation for each channel in the CIE L*a*b* color space. The lower the measurement, the less noise in the image.
Noise and Detail Perceptual scoring
- Texture (bright light): 4.5 out of 5
- Texture (low light): 3.0 out of 5
- Noise (bright light): 3.5 out of 5
- Noise (low light) 2.0 out of 5
Phone cameras, like entry-level compact cameras, tend to suffer from artifacts such as sharpening halos, color fringing, vignetting (shading) and distortion, which can impact on the visual appeal of the end result. DxOMark engineers measure and analyse a range of artifacts. Their findings after testing the Blackberry Z10 are shown below:
- Slight loss of sharpness in image corners
- Strong color fringing
- Slight ringing
- Sharpness 4.0 out of 5
- Color fringing 4.0 out of 5
- Ringing center: 14.1%
- Ringing corner 6.1%
- Max geometric distortion -0.29%
- Luminance shading 26%
Distortion and Chromatic Aberrations
DxOMark also tests autofocus accuracy and reliability by measuring how much the accutance -- sharpness -- varies with each shot over a series of 30 exposures (defocusing then using the autofocus for each one). As with other tests these results are dependant on the viewing conditions (a little bit out of focus matters a lot less with a small web image than a full 8MP shot viewed at 100%). Using the 8MP equivalent condition the Blackberry Z10 results are decent but not quite up there with the very best. The overall score is 75/100 in bright light and 64/100 in low light.
- Autofocus is accurate and repeatable in bright light conditions
- Good sharpness levels even in low light
- Autofocus is slow
DxOMark scored the Blackberry Z10 62/100 overall for its flash performance, deducting points for occasional white balance issues in mixed light.
- Good detail preservation, exposure and color rendering
- Stable autofocus with flash
- Strong noise
- White balance is slightly blue with no light and turns red when flash is mixed with tungsten lighting
- Color shading when mixed with tungsten light source
Overall DxOMark Mobile score for Photo: 67 / 100
DxOMark engineers put phone cameras through a similarly grueling set of video tests, and you can read their full findings on the DxOMark website here. We'll simply summarize for you. DxOMark found the Blackberry Z10's exposure and color reproduction to be good. However, the white balance is unreliable in tungsten light and image stabilization performance is under par.
- Reactive autofocus with some tracking abilities
- Visible color non uniformities
- Perfectible texture reproduction
- Perfectible video stabilization
Overall DxOMark Mobile score for Video: 66 / 100
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