DxOMark Mobile Report

Summary

With a DxOMark Mobile score of 69 the Amazon Fire Phone takes the number 18 spot in the DxOMark smartphone rankings, directly ahead of the HTC One M8. The DxOMark team reports the Fire Phone images show "good exposure in low light and bright light conditions and "nice details preservation outdoors". They also found the autofocus to perform very speedily in bright light. On the downside the testers found that "white balance is yellow/green in sunny conditions, sharpness is different between the center and the edges of the frame" and there is "strong flare visible in sunny backlight outdoor conditions and strong color fringing." They also found the autofocus to be unstable. Shooting with flash results in strong vignetting and the white balance is inaccurate when flash is mixed with tungsten light.

In the Amazon Fire Phone's video mode the recorded footage shows "good overall exposure for scenes with static lighting conditions and good color rendering even in low light". The testers also found the optical image stabilization system to work very efficiently when shooting hand-held. On the downside, the "autofocus is unstable and struggles to focus in low light, especially at macro distances". There is also some noticeable "stepping" when exposure is adjusted and "white balance adjustement is not smooth for sudden changes of lighting conditions.

Still Photography

Color, Exposure and Contrast

The DxOMark team found that the Amazon Fire Phone images show "good overall exposure in low light and bright light conditions" but "the white balance is yellow/green in sunny conditions, a slight color cast is noticeable under tungsten light and some colors are over-saturated.

Overall DxOMark awarded the Amazon Fire Phone scores of:

  • 4.3 out of 5 for Exposure
  • 3.5 out of 5 for White Balance accuracy
  • 3.2 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
  • 4.1 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 on the Amazon Fire Phone images show "nice details preservation outdoors" but "luminance noise is visible in areas of plain color even in bright light and strong luminance and chroma noise is visible 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.
Luminance texture acutance is a touch higher in daylight than under tungsten light but the difference won't be noticeable in normal shooting. 
In terms of texture acutance, the Amazon Fire Phone performs well in bright light but is trailing behind the competition in dimmer 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 bright light the Fire Phone's measured edge acutance is at the same level as the iPhone 6 but cannot keep up with the competition in low light conditions.    
Edge acutance is at a high level in bright light but drops noticeably in darker conditions. 

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 are high in low tungsten light but drop considerably as the illumination gets brighter.
Daylight noise values are a touch lower than under tungsten illumination.
In bright light the Fire Phone's noise values are on par with the competition but among the highest in low light conditions. 

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 Amazon Fire Phone were:

Natural scene

  • Texture (bright light): 4.7 out of 5
  • Texture (low light): 3.5 out of 5
  • Noise (bright light): 3.7 out of 5
  • Noise (low light) 2.8 out of 5
Bright light sample shot. 
100% crop: good detail but noise in areas of plain color
Low light (20 Lux) studio shot.
100% crop: fine detail is smeared by noise reduction
100% crop: both luminance and chroma noise are visible in low light shots

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 Amazon Fire Phone are shown below:

  • Strong flare in sunny backlight conditions
  • Softness toward the edges of the frame
  • Strong color fringing noticeable.
  • Moire patters noticeable
Strong flare in some backlight situations
Strong color fringing (100%crop)

Perceptual scores

  • Sharpness 3.4 out of 5
  • Color fringing 2.9 out of 5

Measured findings

  • Ringing center 11.6%
  • Ringing corner 1.0%
  • Max geometric distortion -0.3%
  • Luminance shading 18.9%

Distortion and Chromatic Aberrations

The graph shows the magnification from center to edge (with the center normalized to 1). The Amazon Fire Phone shows a slight pincushion distortion, which is not going to be noticeable in normal photography.
The Amazon Fire Phone images show stronger than usual lateral chromatic aberrations which are visible in some high-contrast shooting situations.

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 Amazon Fire Phone is more unstable than many competitors. The overall score is 65/100 in bright light and 40/100 in low light.

Pros: 

  • Fast autofocus in bright light

Cons: 

  • Autofocus not repeatable and inaccurate
Autofocus repeatability - average acutance difference with best focus: low light 22.60%, bright light 15.32%

Flash

DxOMark scored the Amazon Fire Phone 61/100 overall for its flash performance which is lower than most of the competition. 

Pros: 

  • Good detail and color if flash is the only light source

Cons:

  • Strong vignetting
  • Inaccurate white balance when flash is mixed with tungsten light

Overall DxOMark Mobile Score for Photo: 68/ 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. Overall DxOMark found the Amazon Fire Phone's video performance to be decent in good light, with good exposure and detail. However, in low light, the AD is unstable and both exposure and white balance adjustments are not smooth.   

Pros: 

  • Good overall exposure in static lighting conditions
  • Good color rendering is good even in low light
  • Good detail and low noise levels in bright light 
  • Optical Stabilization efficiently reduces camera shake

Cons: 

  • Unstable autofocus in in low light conditions, especially at macro distance
  • Noticeable stepping during exposure adjustment
  • White balance adjustment is not smooth when lighting conditions change suddenly
  • Stabilization not efficient for walking motion

Overall DxOMark Mobile Score for Video: 72 / 100