Studio Comparison (low light)
The low light scene is shot with Auto White Balance, to show how the camera's JPEGs look under artificial light. Any 'keep warm tone' options are left at their default setting.
The low light scene Raws are processed to demonstrate the capability of cameras in low-light shooting situations. Noise reduction is minimized and the white balance is neutralized to reveal blue channel noise. The black level is lifted to prevent noise being hidden by clipping. A standardized amount of sharpening is applied in Photoshop.
In terms of luminance noise and detail, there's not a whole lot of difference between the a7's performance in low light and good light throughout the range of available ISOs. Sony has done an excellent job of reducing color noise in JPEGs, even at the highest sensitivities.
Switching to Raw, you won't start to notice chroma noise until, and even then, there's very little. It doesn't become prominent until you reach , though detail loss doesn't become an issue until . At in good light, there's very little left to work with at .