Performance and Image Quality

The Samsung Galaxy S3 is the current Samsung Mobile flagship phone featuring the latest generation of mobile processor (quad- or dual-core, depending on the region in which you buy the phone) and as such the S3 is very responsive and reliable in general operation. Apps, including the camera app, open in the blink of an eye and you can run a large number of apps at the same time without any discernible loss of performance.

In the camera app itself the touch-to-focus function works well. In good light focus acquisition is very swift, when the light gets dimmer focus time increases slightly and in very low light there can be some focus hunting but none of this is any worse than expected or indeed most entry level compact cameras.

There's one area in which the S3 beats not only most entry-level compact cameras but also more advanced models: shutter lag. In the documentation Samsung lists 'zero shutter lag' as one of the phone's features and it's no exaggeration. An image is captured as soon as you touch the virtual shutter button on the screen and shot-so-shot times are almost instant. You can take an entire series of images in very quick succession by quickly tapping the shutter button. This is quite impressive, and one area in which the S3 trumps not only competitive smartphones but also many compact cameras.

Daylight, Low ISO

Like all digital cameras, the Samsung Galaxy produces its best results in good light. In bright and sunny conditions images show good detail across the frame but some luminance noise is visible in areas of plain color such as blue skies. Exposure is almost always very good but dynamic range limitations become visible in high contrast situations, with 'blown out' highlight areas. In these occasions you can dial in some negative exposure compensation or - if you're shooting static subjects - you can switch to the HDR mode.

In good light the Galaxy S3 shows good detail but limited dynamic range means some highlight clipping can occur, as seen in the sky in this image.
100% crop
In natural light the S3 produces natural skin tones and very good white balance.
100% crop
Detail in bright light is good but strong sharpening and noise reduction means that low contrast detail, such as the distant foliage in this image can appear a little 'mushy'.
100% crop
Highlight clipping can be a problem in bright conditions.
100% crop
In sunny conditions and scenes with lots of high contrast detail the Samsung produces results that are comparable to dedicated cameras.
100% crop

Low Light, High ISO

The Samsung Galaxy S3 offer manual control over ISO but not all settings are available in manual mode. You can choose on a range from ISO 100 - 800 but in Auto mode the S3 goes both below and above this range, capturing images at ISO 80 and 1600 respectively.  This is roughly in line with other current top-of-the-line Android smartphones but the Apple iPhone 5 offers a nominal maximum ISO 3200 (albeit one enabled by pixel-binning). 

As you would expect from an image capturing device with such tiny sensors as used in the current crop of smartphones the Samsung S3's image quality deteriorates quickly as you increase the ISO sensitivity, with noise, noise reduction artifacts and detail smearing creeping in quite aggressively. Nevertheless, images are good enough for typical web use up to the highest settings, just don't expect miracles.

At ISO 500 the S3 images show visible noise and deterioration of detail but image quality is still good enough for web use.
 100% crop
At the maximum ISO images are very noisy with a lot of smudged detail. In dark environments such as this bar ISO 1600 is not enough for moving subjects and as a consequence, people in your images almost always end up blurry.
 100% crop
 This ISO 1000 shot has plenty of visible noise but shows good high-contrast detail and pleasantly-saturated colors.
 100% crop

With no way to manually set the shutter speed and a maximum ISO of 1600 you inevitably run into limitations in very low light environments. The S3 attempts to keep shutter speeds a a hand-holdable levels and does not appear to go any lower than 1/30 sec without using the flash which means that very dark scenes like the bar in the images below will end up under-exposed. There is nothing you can do about it. 

 With a maximum sensitivity of ISO 1600 in dark interiors such as this bar the camera hits its exposure limit...

 ...and you end up with an underexposed shot.

In general in low light scenes the S3 appear to favor slower shutter speeds over increasing sensitivity which can result in motion blur if moving subjects are in the scene. Low light performance on any smartphone is, compared to dedicated digital cameras, not great and the S3 is roughly in line with the competition but it's worth keeping these limitations in mind when shooting in dark interiors.