DxOMark Mobile Report: Sony Xperia z5
The latest generation of Sony's high-end smartphones comes with some significant changes in the camera specification for the first time since the Xperia Z1. A 23MP 1/2.4" BSI CMOS sensor is paired with an F2.0 lens and dual-LED flash. Sony claims the hybrid AF system, which combines contrast and phase detect technologies, makes the Z5 series the fastest focusing camera phones in the business at 0.03 seconds. The 4.6-inch 720p Xperia Z5 Compact, the 5.2-inch 1080p Xperia Z5 and the 5.5-inch 2160p Xperia Z5 Premium all come with the same camera module, allowing consumers to pick the screen size and resolution they prefer without compromising on camera performance.
With a DxOMark Mobile score of 87 the Sony Xperia Z5 is the new number one in the DxOMark smartphone rankings, placing itself in front of the Samsung Galaxy S6 and the LG G4. The DxOMark team reports that the Z5's autofocus is "impressive in all conditions" and "the best tested to date". Images show "very good white balance and color rendering in most situations" and "good detail preservation outdoors and in low light conditions". Noise is finely grained and when shooting with flash images show "good exposure, pleasant white balance and good detail preservation". On the downside, images show "visible blue sky saturation" and "skies are burnt in high-contrast scenes". Flash images show some vignetting.
The video mode comes with "very impressive stabilization that is far ahead of competitors" and "good autofocus behavior". Footage shows "good detail preservation and noise levels" as well as "accurate white balance and color rendering". On the downside, "sometimes tremors are visible, even when using a tripod", exposure transition is sometimes very slow, resulting in clipped highlights and "in low light conditions, autofocus is sometimes slow". "Color shading is visible in low light and indoor conditions".
Color, Exposure and Contrast
The DxOMark team found that when shooting with the Sony Xperia Z5 images show "good white balance in most situations and no visible color shading". In low light a "pleasant and natural yellow cast is noticeable". As a negative, it was noted that in high-contrast scenes you can end up with blown highlights in the sky.
Overall DxOMark awarded the Sony Xperia Z5 scores of:
- 4.5 out of 5 for Exposure
- 4.6 out of 5 for White Balance accuracy
- 4.4 out of 5 for Color shading in low light*
- 4.4 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 noise in the Sony Xperia Z5's images in low light conditions is pleasantly fine grained. They also found "good detail preservation outdoors and in low light conditions and no chroma noise". On the downside, testers found texture to be limited by the 8MP default resolution.
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 (such as fine foliage, hair or 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's 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 edges are sharp and if fine details are visible. In-camera processing means that 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 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 the 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): 4.8 out of 5
- Texture (low light): 3.6 out of 5
- Noise (bright light): 4.1 out of 5
- Noise (low light) 3.8 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 have an impact on the visual appeal of the end result. DxOMark engineers measure and analyze a range of artifacts. Their findings after testing the Sony Xperia Z5 are shown below:
- Strong blue sky saturation
- Loss of sharpness in the corners
- Slight moiré patterns are noticeable
- Sharpness 4.5 out of 5
- Color fringing 4.5 out of 5
- Ringing center 16.6%
- Ringing corner 9.1%
- Max geometric distortion -0.3%
- Luminance shading 23.1%
Distortion and Chromatic Aberrations
DxOMark also tests autofocus accuracy and reliability by measuring how much the acutance - or 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 dependent 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 setting, the Sony Xperia Z5 performs very well in all light conditions. The overall score is 98/100 in bright light and 93/100 in low light.
- Fast and accurate autofocus in bright light and low light conditions
- Very little overshooting
- AF speed decreases slightly in low light conditions
The Sony Xperia Z5 comes with a single-LED flash and DxOMark scored the camera 91/100 overall for its flash performance.
- Good exposure and detail preservation
- Accurate white balance and color preservation
- Light attenuation visible on corners
Overall DxOMark Mobile Score for Photo: 87 / 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. Overall, DxOMark found the Sony Xperia Z5's video footage to be very well stabilized and to show very good detail and noise levels. On the downside, exposure sometimes is a little slow adapting to changes in brightness.
- Very good stabilization, even for walking motion
- Good autofocus behavior
- Good detail preservation and noise levels
- Accurate white balance and color rendering
- Sometimes tremors are visible, even when using a tripod
- Exposure transition is sometimes very slow, resulting in highlight clipping
- In low light conditions, autofocus is sometimes slow to trigger
- Color shading is visible in low light and indoor conditions
Overall DxOMark Mobile Score for Video: 86 / 100
DXOMark Image Quality Assessment
With a DxOMark Mobile score of 87 the Sony Xperia Z5 is the new number one in the DxOMark smartphone rankings, achieving the most points of all tested models so far in both still image and video categories. The DxOMark team was particularly impressed by the Sony's fast and accurate AF system, good detail retention and finally grained noise. The only points of criticism were a tendency towards channel clipping in blue skies and noticeable vignetting when shooting with flash.
In video mode the testers liked the very efficient digital stabilization and good AF behavior but color shading can become visible when shooting indoors or in low light. For a more detailed analysis, visit www.dxomark.com.
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