DxOMark Mobile Report: Samsung Galaxy Note II

DxO Lab uses industrial-quality scientific measurements to inform its DxOMark Mobile Reports. Its imaging experts analyze 14 aspects of mobile imaging for each report, including detailed image quality assessment, flash performance, autofocus reliability and more to calculate a final score. 

Summary

With a DxOMark Mobile score of 72 the  Samsung Galaxy Note II ranks alongside the iPhone 5 and the Samsung Galaxy S3. The latter especially comes as no surprise since the Note II’s camera specs are as good as identical to those of the S3, though Samsung won’t confirm that they use the exact same hardware.

The DxOMark team report that the Samsung Galaxy Note II's autofocus is "accurate, repeatable and smooth." When it comes to image capture,  "colors are vivid and pleasant."

On the downside: Images show "strong loss of texture due to an excessive noise reduction in low light," and  "in challenging outdoor conditions some parts of images can be burnt out." DxOMark found the flash to be dark and "slight noticeable color shading under different lightings."

In video mode, DxOMark's engineers reported that the Samsung Galaxy Note II offers good exposure and colors, but on the downside video footage shows "low texture reproduction in low light" and "strong noise under low-light conditions."

Color, Exposure and Contrast

Still Photography

The DxOMark team found that the Samsung Galaxy Note II produces  images with "vivid and pleasant" colors, and with "good auto-exposure." They also found "white balance is stable and accurate."

However, under challenging conditions, "images can be partly burnt out." Slight color shading is also noticeable", and in low tungsten light "a red cast is sometimes noticeable."

DxOMark scored the Samsung Galaxy Note II at 81/100 for exposure and contrast, and 78/100 for color in bright light and 75/100 in low light.   

Overall DxOMark awarded the Samsung Galaxy Note II scores of:

  • 4.3 out of 5 for Exposure
  • 4.5 out of 5 for White Balance accuracy
  • 3.5 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
  • 4.0 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 Samsung Galaxy Note II image output shows "nice detail in outdoor pictures" and acceptable noise levels in low-light conditions. On the other hand, "noise reduction is too strong causing a strong loss of detail in low light" and "sharpening on contoures is too strong, causing a sharpness imbalance between edges and textured areas."

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 (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.

A detail of  target made of a dead leaves pattern, designed to measure Texture Acutance. It is 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 of the same 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 a 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 showing only the 8MP equivalent values, which gives us a level playing field for comparison between phone cameras with different megapixel values by normalizing all to 8MP, suitable for fairly large prints. DxOMark also offer this data for lower resolution use-cases (web and on-screen). For more information on DxOMark's testing methodology and Acutance measurements please visit the website at www.dxomark.com.
 Texture acutance is nearly identical for daylight and tungsten light sources.
The Note II can't quite keep up with the iPhone 5 in low light conditions but is on par in brighter light. The Nokia 808 with its PureView technology is a cut above the rest.

Edge Acutance

Edge acutance is a measure of the sharpness of the edges in images captured by the phone's camera, and again we're only looking at the most demanding of the three viewing conditions that DxOMark reports on, "8MP equivalent."
The Note II's ability to retain fine texture in images increases noticeably from very low light (20 Lux, for example a floodlit building at night) to 100 Lux (very dark overcast day) but then plateaus through 700 Lux (outdoors on an overcast day). Results under artificial light are almost identical.
In terms of edge acutance the Note II trails slightly behind the iPhone 5 and Nokia 808 at lower light levels but measures better at 100 and 700 lux. However, this is probably a reflection of the high sharpening levels applied to the Samsung images.

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 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.

Visual noise is high in low light levels and decreases to much lower levels in brighter light. Most of the measures noise is luminance grain as chroma noise is being eliminated by noise reduction.
Visual noise is slightly higher in low light scenes lit with tungsten than natural low light settings.
In low light the Nokia 808 is the clear winner here, thanks to its groundbreaking 'PureView' oversampling technology. However, the other devices can catch up in bright light. The Note II does well and produces lower visual noise levels than the iPhone 5 at 20 and 100 Lux.

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 Samsung Galaxy Note II were as follows:

Natural scene

  • 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) 3.0 out of 5
Bright light sample shot
  100% crop shows a lot of fine detail
Low light (20 Lux) studio shot
In low light noise reduction causes a loss of fine detail.
In low tungsten light crops show a lot of smeared detail but good detail but are blighted by high luminance noise levels.

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 impact on the visual appeal of the end result. DxOMark engineers measure and analyse a range of artifacts. Their findings after testing the Samsung Galaxy Note II are shown below:

Pros:

  • No major problems

Cons 

  • Ringing is noticeable at 100% scale due to too-strong sharpening
  • Significant loss of sharpness in low-light conditions

Perceptual scores

  • Sharpness 4.0 out of 5
  • Color fringing 4.5 out of 5

Measured findings

  • Ringing center: 18.7%
  • Ringing corner 8.9%
  • Max geometric distortion 0.34%
  • Luminance shading 17%

Distortion and Chromatic Aberrations

The graph shows the magnification from center to edge (with the center normalized to 1). The Samsung Galaxy Note II shows a slight complex distortion of 0.34%. You are not going to notice this in normal photography.
Lateral chromatic abberations minimal; chromatic abberation this small are not seen by most observers.

Autofocus

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 Galaxy Note II results are decent but not quite up there with the very best. The overall score is 79/100 in bright light and 68/100 in low light.

Pros: 

  • In bright light, autofocus is fast, accurate and reliable in both auto mode and trigger modes
  • Scene change detection is good and automatic focsuing is accurate. 

Cons: 

  • No face detection
  • Autofocus is slightly less repeatable in low light
  • Sharpness is slightly different in auto mode and trigger mode
    Autofocus repeatability - average acutance difference with best focus: low light 3.95%, bright light 6.66%

Flash

DxOMark scored the Galaxy Note II 70/100 overall for its flash performance, deducting points for dark image corners and inaccurate colors in mixed lighting situations indoors.

Pros: 

  • Good overall image quality with or without additional light source
  • Nice colors and sharp details

Cons: 

  • Colors are sometimes neither accurate nor uniform when flash is mixed with a tungsten illuminant
  • With no additional light, image corners are dark
  • No red eye correction

Overall DxOMark Mobile score for Photo: 73 / 100


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. We'll simply summarize for you: DxOMark found the Samsung Galaxy Note II's video capture good, though the device struggled in low-light conditions.

Pros: 

  • Good exposure and colors.
  • Autofocus is quite fast and stable.

Cons: 

  • Low texture reproduction in low light
  • Strong noise under low-light conditions. 

Overall DxOMark Mobile score for Video: 71 / 100