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 Panasonic LX7 match the marked ISOs within 1/6 stop accuracy, meaning ISO 100 indicated = ISO 100 measured.
Noise and Noise Reduction (JPEG)
At default noise reduction settings, the LX7's output is impressively noise-free at its lowest ISO sensitivities, up to ISO 400. A hint of granularity can be seen in mid-tones, but if you want buttery-smooth images you can always bump noise reduction up, at which point noise is barely visible until ISO 1600. Fine detail does get a little smoothed away in the process though. For maximum detail reproduction, you can turn noise reduction down, which gives you a little bit of detail back, but the difference is subtle up to ISO 1600. Above this setting, the LX7's images are fairly noisy whatever NR setting you choose, but they compare very well to competitive cameras, as you can see in the images on this page, and an impressive amount of detail is still visible at ISO 3200.
RAW noise (ACR 6.7, noise reduction set to zero)
The difference between the LX7's image quality and that of its 10MP peers is not as significant in Raw mode as it is in JPEG. At the lowest ISO sensitivities the LX7 captures an equivalent amount of detail to its nearest competitors, but offers slightly lower noise levels at high ISO sensitivities. Realistically though, with a moderate amount of noise reduction applied, the LX7's Raw output is useable right up to ISO 3200. ISO 6400 is pretty gritty, still competitive alongside other cameras in this class.
Fujifilm X10: Note that we usually include Raw files processed through Adobe Camera Raw (ACR) in our studio comparison tool because they reveal the potential of the sensor, unencumbered by in-camera image quality parameters and JPEG compression. However, the X10, with its unique EXR sensor technology has less than optimal support from third party raw converters. ACR does officially support the X10 but, as you will see in the samples below, sharpness and detail are noticeably lower than results provided by in-camera Raw conversions.