Summary

With a DxOMark Mobile score of 74 the Nokia Lumia 1020 slots in at the number four spot in the DxOMark smartphone ranking, just below the Samsung Galaxy S4 and above the iPhone 5. However, the overall score is pulled down by a relatively low video score of 64 points. The photo score of 79 puts the 1020 in a joint second place with the Galaxy S4 in that category, behind its older brother, the Nokia 808.  

The DxOMark team reports that the Nokia Lumia 1020 captures images with "excellent detail preservation both in low and bright light conditions, very low noise levels with no chroma component". "In extreme low light conditions, exposure stays good when other camera phones are failing". The Nokia's xenon flash also performs well, with "good exposure, color, white balance, texture and noise" and the DxO engineers found the 1020's AF to be fast and precise.

On the downside there is "strong color shading with indoor lighting and sometimes outdoors", "in low light conditions, exposure is too long which may cause motion blur", "images are sometimes slightly underexposed outdoors", white balance sometimes produces blue cast outdoors or with fluorescent lightings" and there is "strong flare noticeable in presence of a strong light source".

In video mode, DxOMark's engineers reported that the Nokia Lumia 1020 renders "good textures in bright light conditions" but there is also "strong row noise", "visible blocking artifacts" and "walking movements are not corrected by the video stabilization". "Autofocus oscillations are visible during refocusing" and "over-correction of the video stabilization when the device is on tripod" were observed.

Still Photography

Color, Exposure and Contrast

The DxOMark team found that on the Nokia Lumia 1020 "in extreme low light, the exposure stays good thanks to longer exposure time" and the images show "pleasant colors outdoors".

However, "strong color shading with some illuminants (e.g. tungsten or fluorescent lightings)" is visible", "white balance is sometimes blueish outdoors". The testers also observed "some white balance variations with indoor lightings" and some underexposure outdoors. Because of this DxOMark scored the Nokia Lumia 1020 at 64/100 for color in bright light and 49/100 in low light.   

A strong color cast in the center of the frame can be observed in the sample to the left.

Overall DxOMark awarded the Nokia Lumia 1020 scores of:

  • 4.2 out of 5 for Exposure
  • 3.0 out of 5 for White Balance accuracy
  • 2.5 out of 5 for Color shading in low light*
  • 3.5 out of 5 for Color shading in bright light*
  • 3.5 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 Nokia Lumia 1020 image output shows "excellent detail preservation both in low and bright light, low noise level both in low and bright light and no chroma noise". However, "in low light conditions, exposure time is too long (1/4s compared to 1/15s for other camera phones at 10 lux), which can cause motion blur".

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 good and very similar for daylight and tungsten light sources.
In terms of texture acutance the Nokia Lumia 1020 is excellent across all light levels. 

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 Nokia Lumia 1020 mode produces consistently sharp edges in all lighting conditions. 
The measured edge acutance of the Nokia Lumia 1020 is identical to the 808. Both camera phones uses very subtle sharpening compared to some competitors, but still offer very competitive edge acutance.

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 on the Nokia Lumia 1020 is remarkably low, thanks to the large 1/1.5-inch sensor.
The results in tungsten light are almost identical to daylight.
 Although the 1020 cannot quite keep up with its older brother, the Nokia 808, it leaves the competition from Samsung and Apple behind. 

Noise and Detail Perceptual scoring

DxOMark engineers don't just point camera phones at charts, they also take and analyse scores of real-world shots and score them accordingly. Their findings for the NokiaLumia 1020 were:

Natural scene

  • Texture (bright light): 4.8 out of 5
  • Texture (low light): 4.3 out of 5
  • Noise (bright light): 4.3 out of 5
  • Noise (low light) 4.3 out of 5
Bright light sample shot
"Outdoors, a lot of fine detail is visible"
Low light (20 Lux) studio shot
"Noise levels remain extremely low. However, exposure time is slightly too long (1/4s here) which may cause motion blur"
"Almost no loss of details compared to bright light conditions"

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 Nokia Lumia 1020 are shown below:

  • Loss of sharpness in image corners
  • Noticeable flare in pictures containing burnt-out areas

Perceptual scores

  • Sharpness 4.0 out of 5
  • Color fringing 3.0 out of 5

Measured findings

  • Ringing center: 7.3%
  • Ringing corner 0.5%
  • Max geometric distortion -0.3%
  • Luminance shading 18.8%

Distortion and Chromatic Aberrations

The graph shows the magnification from center to edge (with the center normalized to 1). The Nokia Lumia 1020 shows a slight pincushion distortion that you are not going to notice in normal photography.
Very slight color fringes (red and blue) are noticeable in real world shots (lateral chromatic aberrations).

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 Nokia Lumia 1020 results are up there with the very best. The overall score is 88/100 in bright light and 79/100 in low light.

Pros: 

  • Fast AF both in low and bright light
  • Precise AF both using the mechanical trigger and touch screen

Cons: 

  • Overshooting in all situations
Autofocus repeatability - average acutance difference with best focus: low light 5.0%, bright light 6.5%

Flash

DxOMark scored the Nokia Lumia 1020 79/100 overall for its flash performance, thanks to good overall flash behavior.

Pros: 

  • Good exposure, low noise level, good detail preservation
  • Good white balance and color rendering

Cons: 

  • n/a

Overall DxOMark Mobile score for Photo: 79 / 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 Nokia Lumia 1020's exposure and color reproduction to be good. However, the white balance is unreliable in tungsten light and image stabilization performance is under par.

Pros: 

  • Good textures in bright light conditions

Cons: 

  • Strong row noise
  • Visible blocking artifacts
  • Walking movements are not corrected by the video stabilization
  • Autofocus oscillations are visible during refocusing.
  • Over-correction of the video stabilization when the device is on tripod

Overall DxOMark Mobile score for Video: 64 / 100