Samsung Galaxy S3 Camera Review

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.

The Samsung Galaxy S3'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 stays on the same high level for 700 Lux (outdoors on an overcast day). Results under artificial light are almost identical.

The Galaxy S3 trails behind the competition at very low light levels but catches up and has a slight edge over the other phones in this comparison at brighter light of 100 and 700 Lux. However, this is probably a reflection of the high sharpening levels applied to the S3 images.

Visual Noise

Visual noise is high at very low light levels, but drops to a marginal level once you get out into the daylight. Most of the measures noise is luminance grain as chroma noise is being eliminated by noise reduction.

The results under tungsten light are almost identical to the daylight measurements.

The Nokia 808 is the clear winner here, thanks to its groundbreaking 'PureView' oversampling technology. The Samsung Galaxy S3 is pretty much on the same level as the iPhone 5 while the iPhone 4S is noisier than the competition across all light levels.

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 Samsung Galaxy S3 were:

• 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 "many fine details"

Low light (20 Lux) studio shot	Some fine detail is lost.

Fine detail is blurred but noise remains at acceptable 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 SIII are shown below:

Pros:

• No major problems

Cons 

• Rinign noticeable at a 100% scale, due to strong sharpening filter
• 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: 17.7%
• Ringing corner 5.9%
• Max geometric distortion 0.35%
• Luminance shading 17%

Distortion & Chromatic Aberrations

the graph shows the magnification from center to edge (with the center normalized to 1). The Samsung Galaxy SIII shows a very slight complex distortion, with a maximum geometric distortion of 0.35%. 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%). Even using the 8MP equiv. condition the Samsung Galaxy SIII did very well, earning an overall score of 91/100 in bright light and 71/100 in low light.

Pros: 

• At 700 Lux, the autofocus is fast, accurate and reliable in both auto mode and trigger mode
• Scene change detection is good and automatic focusing is accurate
• Automatic face detection

Cons: 

• Autofocus slightly less repeatable in low light

Autofocus repeatability - average acutance difference with best focus: Low light 2.64%, Bright light 0.84%

Flash

DxOMark scored the Samsung Galaxy SIII 81/100 overall for its flash performance, deducting points for occasional white balance issues in mixed light and the lack of red-eye reduction.

Pros: 

• Good overall image quality with or without additional light source: nice colors, good exposure and sharp details

Cons: 

• Colors are sometimes neither accurate nor uniform when mixed with a tungsten illuminant 
• No red eye correction

Overall DxOMark Mobile score for Photo: 73 / 100

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Video Capture

DxOMark engineers put phone cameras through a similarly gruelling set of video tests, and you can read their full findings on the DxOMark website here. We'll simply summarize for you. In bright light DxOMark found the Samsung Galaxy S3 to produce good results with good exposure, pleasant color rendering and free from noise. Lowlight performance was less impressive, with a significant loss of detail and increased amounts of both luminance and chroma noise. Image stabilization only compensates for relatively small movements and the AF can be little unstable in continuous mode (but can be locked).

Pros: 

• Colors and exposure are pleasant.
• Intuitive and reactive autofocus
• Videos are free from noise in bright light conditions.

Cons: 

• Autofocus in continuous mode is unstable, and produces noticeable lens breathing .
• Strong noise in low light conditions.
• Visible color shading under tungsten light source.
• Stabilization does not manage to compensate for walking motions.

Overall DxOMark Mobile score for Video: 71 / 100