DxOMark Mobile report: Google Nexus 6P

Summary

With its 5.7-inch QHD AMOLED display the Nexus 6P is a little smaller than last year's Nexus 6 in terms of both display size and overall dimensions. It comes with an aluminium shell and overall high-end specs. In the camera department the new model features a 12.3MP Sony sensor and an F2.0 aperture. The lack of optical image stabilization should be made up for by large pixels with a size of 1.55 microns, while more phase detection sensors and a laser "time of flight" sensor allow for faster and more precise focusing. 

With a DxOMark Mobile score of 84 the Google Nexus 6P is the new number three in the DxOMark smartphone rankings, placing itself between the Samsung Galaxy S6 and the LG G4. The DxOMark team reports that the Nexus images show "impressive detail preservation in low light conditions, by far the best tested to date and good detail preservation in outdoor conditions". The AF is "accurate and fast in all conditions" and image output shows "good white balance and color rendering in outdoor conditions". Flash behavior is good as well, with "good detail preservation, white balance and color rendering".

On the downside, there are "visible irregularities in exposure, color, texture and noise due to HDR+ mode activation in low light conditions" and "in high-contrast scenes, image highlights are occasionally blown out". The testers also criticized that the camera captures an image when the shutter is pressed, even though the AF has not locked on yet.

In video mode the DxO team liked the "good global exposure, white balance and color rendering, the fast and accurate AF and the low noise levels in all conditions". On the downside, the stabilization causes a strong jello effect, the camera tends to refocus when illumination changes and focus can be lost when tracking. The testers also found that "fine detail is lost in low light conditions and color shading is visible in low light and indoor conditions".

Still Photography

Color, Exposure and Contrast

The DxOMark team found that when shooting with the Google Nexus 6P images "are mostly well exposed, with generally accurate white balance". On the downside, white balance is "slightly pinkish with tungsten illuminants" and in "high-contrast scenes image highlights are occasionally blown out".

Overall DxOMark awarded the Google Nexus 6P scores of:

• 4.5 out of 5 for Exposure
• 4.4 out of 5 for White Balance accuracy
• 3.5 out of 5 for Color shading in low light*
• 4.5 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 Google Nexus 6P images show "good detail preservation in outdoor conditions and in low light". However, "slight noise is visible in both low light and bright light conditions".

Texture Acutance

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.

	A dead leaf pattern is designed to measure texture acutance. It's obtained by drawing random shapes that occlude each other in the plane, like dead leaves falling from a tree. The statistics of this model follow the distribution statistics in natural images.
	In this example from a DSLR without edge enhancement, sharpness seems equal on edge and on texture. Many details are visible in the texture.
	In this second example, edges have been digitally enhanced, and the edge looks over sharp, with visible processing halos ("ringing"). On the texture part, many details have disappeared.

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.

Note: Acutance is a single value metric calculated from a MTF result. Acutance is used to assess the sharpness of an image as viewed by the human visual system, and is dependent on the viewing conditions (size of image, size of screen or print, viewing distance). Only the values of texture acutance are given here. The measurements are expressed as a percentage of the theoretical maximum for the chosen viewing condition. The higher the score, the more details can be seen in an image. 

 

For all DxOMark Mobile data presented on connect.dpreview.com we're only showing 8MP equivalent values, which gives us a level playing field for comparison between smartphone cameras with different megapixel values by normalizing all to 8MP (suitable for fairly large prints). DxOMark also offers this data for lower resolution use-cases (web and onscreen). For more information on DxOMark's testing methodology and acutance measurements please visit the website at www.dxomark.com.

Luminance texture acutance decreases only slightly in low light.

Texture accutance is among the best in low light but cannot quite keep up with the Moto X Style and Galaxy S6 in bright conditions.

Edge Acutance

Edge acutance is a measure of edge sharpness in images captured by the phone's camera. Again we're only looking at the most demanding of the three viewing conditions that DxOMark reports on - the 8MP equivalent.

In terms of edge acutance the Google smartphone is trailing behind the competition.

Edge acutance decreases in lower light.

Visual Noise

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 levels increase noticeably in low light.

In terms of measured noise the Nexus 6P is a touch higher than the competitors in our comparison graph.

Noise and Detail Perceptual scoring

DxOMark engineers don't just point camera phones at charts, they also take and analyze scores of real-world shots and score them accordingly. Their findings for the Google Nexus 6P were:

Natural scene

• Texture (bright light): 4.8 out of 5
• Texture (low light): 4.1 out of 5
• Noise (bright light): 4.1 out of 5
• Noise (low light) 4.1 out of 5

Bright light sample shot

100% crop: some noise is noticeable	100% crop: good detail preservation in outdoor images

Low light (20 Lux) studio shot

100% crop: luminance noise is noticeable	100% crop: impressive detail preservation

Artifacts

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 Google Nexus 6P are shown below:

• Visible irregularities in exposure, color, texture and noise due to HDR+ mode activation in low light conditions
• Strong moiré
• Visible ringing in outdoor conditions
• Blue sky saturation occurs in sunny scenes
• Slight color fringing noticeable

100% crop: strong Moiré

Perceptual Scores

• Sharpness 3.8 out of 5
• Color fringing 3.1 out of 5

Measured findings

• Ringing center 7.8%
• Ringing corner 3.0%
• Max geometric distortion -0.4%
• Luminance shading 19.7%

Distortion and Chromatic Aberrations

The graph shows the magnification from center to edge (with the center normalized to 1). The Google Nexus 6P shows a slight pincushion distortion, which you are not going to notice in normal photography.

Measured levels of lateral chromatic aberration are very low.

Autofocus

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 Google Nexus 6P puts in a decent performance in all light levels. The overall score is 95/100 in bright light and 81/100 in low light.

Pros: 

• Generally accurate and fast autofocus in all conditions
• Very stable autofocus in low light conditions

Cons: 

• When triggered, shot is taken before autofocus has converged
• Some instabilities in very bright light, both in macro and infinity position

Autofocus repeatability - average acutance difference with best focus: low light 10.24%, bright light 0.33%

Flash

The Nexus 6P comes with a dual-LED flash and DxOMark scored the camera80/100 overall for its flash performance. 

Pros: 

• Good detail preservation

Cons:

• Strong attenuation in corners
• Some autofocus irregularities
• Strong noise in the corners

Overall DxOMark Mobile Score for Photo: 86 / 100

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Video Capture

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 Nexus 6P's video footage to be well exposed, with good AF and low noise levels. However, stabilization caused a strong jello effect and color shading is noticeable in low light.

Pros: 

• Good global exposure, white balance and color rendering
• Fast and accurate autofocus
• Low noise level in all conditions

Cons: 

• Strong jello effect caused by stabilization
• Visible refocusing during illuminant changes and loss of focus during tracking
• Fine detail is lost in low light conditions
• Color shading visible in low light and indoor conditions