DxOMark Mobile Report: Nextbit Robin

Summary

The Nextbit Robin doesn't look much different than most other smartphones, but its Android operating system and hardware have been optimized to make it the first real cloud phone. When the device is connected to Wi-Fi and plugged into the charger it automatically backs up apps and photos to the cloud. When you start running out of local storage space on the device, files and apps you haven't used in a while are automatically archived. In the camera department the Robin comes with a 13MP sensor, phase detection AF, an F2.2 lens, dual-tone LED flash and 4K video support. You can read more about the Nextbit automatic archiving process and how we got on with its camera in our real-life test in the Nextbit Robin quick review.

In its DxOMark test the Nextbit Robin scores 81 points, currently taking the18th position in the DxOMark Mobile ranking. In still image mode the testers liked the "good detail preservation and fast and generally accurate autofocus". On the downside, "noise is very visible in all conditions", chroma noise levels are high, "white balance is sometimes inaccurate in outdoor conditions, mostly with a blue cast" and high-contrast scenes show little shadow detail and some highlight clipping. The test team also criticized  "fringing and demosaicing artifacts and visible ringing".

When shooting video the Robin showed "good autofocus behavior, generally good noise reduction in bright light and good stabilization in bright light conditions". However, testers also found a "loss of detail in low light, and occasional oscillations with exposure adaptation." Some clips also showed "tremors and jitter artifacts".

Still Photography

Color, Exposure and Contrast

The DxOMark team found the Nextbit Robin images to be "mostly well exposed" but also criticized "visible color shading in all conditions, sometimes inaccurate white balance in outdoor conditions" and highlight and shadow clipping in high-contrast scenes. 

Overall DxOMark awarded the Nextbit Robin scores of:

• 4.4 out of 5 for Exposure
• 4.1 out of 5 for White Balance accuracy
• 3.1 out of 5 for Color shading in low light*
• 4.2 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 Nextbit Robin images show well preserved detail in all conditions and that "low light noise has a fine grain". On the downside, "outdoor noise has a large grain, chromatic noise is very visible and luminance noise very noticeable in low light".

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.

Texture acutance is a touch better in daylight than under tungsten illumination.

The Robin performs well in terms of texture acutance, beating the iPhone 6s Plus, but not quite on the same level as Google's Nexus 6P or the Samsung Galaxy S7.

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 Robin is up with the very best.

Edge acutance is consistently high across all light levels.

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.

In low light noise increases noticeably.

The Robin's noise levels are higher than the competition's at all light levels.

Noise and Detail Perceptual scoring

DxOMark engineers don't just point camera phones at charts, they also take and analyze plenty of real-world shots and score them accordingly. Their findings for the Nextbit Robin are:

Natural scene

• Texture (bright light): 4.8 out of 5
• Texture (low light): 3.8 out of 5
• Noise (bright light): 3.6 out of 5
• Noise (low light) 3.1 out of 5

Bright light sample shot

100% crop: large grain luminance noise	100% crop: good detail but visible chroma noise

Low light (20 Lux) studio shot

100% crop: fine luminance noise	100% crop: good detail

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 Nextbit Robin are shown below:

• Fringing and demosaicing artifacts are very visible
• Visible ringing
• Moiré
• Color artifacts

100% crop: fringing	100% crop: visible ringing

Perceptual Scores

• Sharpness 4.4 out of 5
• Color fringing 3.2 out of 5

Measured findings

• Ringing center 16.3%
• Ringing corner 10.1%
• Max geometric distortion -0.3%
• Luminance shading 7.1%

Distortion and Chromatic Aberrations

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

Chromatic aberrations are visible in some images.

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 Nextbit Robin performs well in all light conditions. The overall score is96/100 in bright light and 83/100 in low light.

Pros: 

• Fast and generally accurate autofocus

Cons: 

• Occasional failure in bright light triggered mode
• Some irregularities in low light

Autofocus repeatability - average acutance difference with best focus: low light 5.54%, bright light 3.94%

Flash

The Nextbit Robin edge offers a dual-LED flash for illumination in very low light. DxOMark scored the camera a 80/100 overall for its flash performance. 

Pros: 

• Flash images are well exposed
• Accurate white balance

Cons:

• Noise is visible in areas of plain color 
• Slight autofocus and exposure irregularities