Resolution, noise and sensitivity
In normal use, in bright lighting conditions, images from the E-620 are reasonably clean until around ISO 800, but in subdued light, images taken at ISO 400 start to show some chroma noise in areas of smooth tone. Shooting in raw mode allows greater control over noise reduction, as well as providing a better basis for sharpening and extreme tonal adjustments.
Assuming, as seems very likely, that the base ISO sensitivity of the E-620’s sensor is closer to 200 than 100, we can see here that in a studio environment at ISO 200, the camera is capable of resolving a lot of detail. At higher ISO settings, images from the E-620 are essentially indistinguishable from those shot with the E-30, and it is clear that although noise reduction (which is set by default in JPEG mode) helps to reduce grittiness, when the function is turned off the camera is able to resolve more lines on our test chart.
However, while turning noise reduction off at ISO 3200 means that resolution increases, the corresponding increase in luminance noise renders ‘real-world’ images unattractive, and greatly reduces the density of shadow areas. With noise reduction turned off, the E-620 produces virtually identical noise level readings to the E-30. This graph shows noise levels with noise reduction set to ‘standard’, and it is clear that measured noise levels decrease significantly, although fine detail suffers. That said, sub-A4 prints look fine until ISO 1600, when noise starts to degrade quality. ISO 3200 is best avoided except in emergencies.
These images show sections of images of a resolution chart, still-life scene and a grey card, shot with a 105mm macro lens. We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera’s detail resolution is at the specified sensitivity setting.
