Sony A57 has a 16.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor . You can shoot at maximum resolution of 4912 x 3264 pixels with aspect ratios of 3:2 and 16:9. A57 has a native ISO range of 100 - 16000 which can be boosted to 25600 and it can save files in RAW format which gives you a wider room for post processing.
Sony A57 is not the highest resolution APS-C camera. Fujifilm X-E5 with its 40.0MP sensor is leading in this class. Check the comparison of Sony A57 vs Fujifilm X-E5 or take a look at Highest resolution DSLR cameras list.
Sony A57 DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Sony A57 sensor has been tested by DxO Mark and got an overall score of 75 for its image quality. You can find the details of their analysis of Sony A57 here.
Let's look at how the size of the Sony A57's APS-C sensor compares with other standard sensor sizes.
Comparison image of Sony A57 Sensor Size with other standard sensors
Sensor size is what determines the circle of confusion, and therefore how much
depth of field Sony A57 gives you at any given aperture.
You can
calculate
the exact depth of field for the Sony A57
at any focal length, aperture and subject distance, including the hyperfocal distance
for landscapes and the very shallow focus zone you get with long telephoto lenses.
