The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). In our tests we found that measured ISOs from the a6000 are around 1/3EV more sensitive than the marked ISOs, meaning ISO 100 indicated = ISO 125 measured.
Noise and Noise Reduction (JPEG)
Throughout its sensitivity range, the a6000 appears to perform extremely well in terms of noise, compared to its peers. However, it's important to note that its noise reduction system is context sensitive; it will heavily surpress noise in areas it expects to be smooth, such as the patches we use to measure noise.
The thing that's interesting to note is that, despite this attempt to apply less noise reduction in areas of detail, the a6000 does no better than its peers in retaining the fine texture in the light blue detail crop.
Adobe Camera Raw noise (ACR 8.4, noise reduction set to zero)
Here we look at the RAW files processed through Adobe Camera Raw (in this case version 8.4). Images are brightness matched and processed with all noise reduction options set to zero. Adobe does a degree of noise reduction even when the user-controlled NR is turned off.
The amount of NR applied 'under the hood' is not high, but it does vary by camera (Adobe is attempting to normalize output across different sensors), so inevitably we are still looking at a balance of noise and noise reduction, rather than pure noise levels. However, the use of the most popular third-party RAW converter is intended to give a photographically relevant result, rather than simply comparing sensor performance in an abstract manner.
In terms of both noise and detail retention, it skirts back and forth between the results of the E-M10 and D5300, all of which slightly outperform the Canon EOS 700D / Rebel T5i. This is essentially the performance you'd expect from a contemporary sensor and is in line with other 24MP APS-C sensors on the market.