DxOMark Mobile Report: HTC One M8

Summary

With a DxOMark Mobile score of 68 the HTC One M8 cannot quite keep up with other current flagship phones and slots in at number 15 in the DxOMark smartphone rankings, placing itself between the Samsung Galaxy Note II and Blackberry Z10

The DxOMark team reports the HTC One M8 delivers "nice and pleasant colors outdoors", "good details for outdoor images" and a "fast and precise autofocus in most situations".

On the downside, DxO says the "rendering of high dynamic range scenes is lacking accuracy", "white balance is inaccurate in some situations", the camera shows "significant sharpness instability in low light conditions", there is a "loss of detail and strong noise in low light" and "clearly visible fringing and color shading" can be observed in the images when shooting outdoors.

In video mode the HTC One M8 displayed "good noise reduction" but "white balance is often inaccurate", there is "no video stabilization", "no continuous autofocus" and "visible steps in luminance during exposure changes" can be observed. 

Still Photography

Color, Exposure and Contrast

The DxOMark team found that the HTC One M8 images show "nice and pleasant colors outdoors." However, "some outdoor images of high dynamic range scenes lost a lot of detail in dark area", "white balance is inaccurate in some situations" and there is "visible color shading outdoors and in low light."

Overall DxOMark awarded the HTC One M8 scores of:

  • 3.8 out of 5 for Exposure
  • 3.5 out of 5 for White Balance accuracy
  • 3.0 out of 5 for Color shading in low light*
  • 3.0 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 the HTC One M8 shows "low luminance noise in bright light conditions" but also "strong sharpness instability between shots in low light conditions" and a "loss of detail and strong noise 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 that can be blurred away by noise reduction or obliterated by excessive sharpening (such as fine foliage, hair or fur).

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 similar under daylight and tungsten light and increases slightly as the illumination becomes brighter. 
In terms of texture acutance, the HTC One M8 leads the pack in low light but falls slightly behind in brighter 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 HTC One M8 is trailing the competition almost across the brightness range.  
The HTC One M8's ability to retain sharp edges remains similar 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.

Noise levels in daylight conditions decrease as illumination gets brighter.
Noise levels under tungsten light are a touch higher than in daylight conditions.
The HTC One M8's noise levels are higher than most of the competition. 

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 HTC One M8 were:

Natural scene

  • Texture (bright light): 4.0 out of 5
  • Texture (low light): 3.5 out of 5
  • Noise (bright light): 3.0 out of 5
  • Noise (low light) 2.0 out of 5
Bright light sample shot
100% crop: some noise even at base ISO
Low light (20 Lux) studio shot.
100% crop: chroma noise in textured areas
100% crop: fine detail is suffering in low light

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 HTC One M8 are shown below:

  • No sharpness difference between the center and the corners
  • Strong fringing and ringing
  • Slight aliasing

Perceptual scores

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

Measured findings

  • Ringing center 8.2%
  • Ringing corner 5.7%
  • Max geometric distortion -0.4%
  • Luminance shading 34.8%

Distortion and Chromatic Aberrations

The graph shows the magnification from center to edge (with the center normalized to 1). The HTC One M8 shows slight pincushion distortion, which you are not going to notice in normal photography.
The HTC One M8 shows some lateral chromatic aberrations which are visible in some pictures.

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 HTC One M8 is trailing slightly behind most of the competition in the high-end bracket. The overall score is 79/100 in bright light and 74/100 in low light.

Pros: 

  • Fast autofocus both in low and bright light conditions
  • No loss of accuracy loss in low light

Cons: 

  • Global acutance is not very good
  • Some focus errors in both bright light and low light conditions
Autofocus repeatability - average acutance difference with best focus: low light 5.88%, bright light 8.41%

Flash

DxOMark scored the HTC One M8 71/100 overall for its flash performance which is lower than most of the competition in the high-end smartphone bracket. 

Pros: 

  • Good detail preservation, exposure, color rendering and white balance

Cons: 

  • Flash is not centered in the image
  • Color shading in mixed tungsten light

Overall DxOMark Mobile Score for Photo: 70 / 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. Bottom line: DxOMark found the HTC One M8's overall video footage to show good texture and noise reduction but a lack of stabilization means footage can be shaky and there is visible brightness stepping when the exposure changes during recording. 

Pros: 

  • Good textures
  • Good noise reduction

Cons: 

  • White balance is often inaccurate (red or blue cast depending on illuminant)
  • No video stabilization or continuous autofocus
  • Visible steps in luminance during exposure changes

Overall DxOMark Mobile Score for Video: 63 / 100