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). Note that these tests are based on the sRGB JPEG output of the cameras, in accordance with ISO 12232:2006, the standard used by camera manufacturers.
In our tests we found that measured ISOs from the Panasonic FZ200 match the marked ISOs within 1/6 stop accuracy, meaning ISO 100 indicated = ISO 100 measured.
Noise and Noise Reduction (JPEG)
ISO range noise comparison
Up to and including ISO 400, noise isn't really an issue, visually, and has only a slight impact upon image quality assuming non-critical output. But at ISO 800 and above, noise really takes a bite out of resolution at default NR settings.
At default NR settings, the FZ200's measured noise is on a par with other cameras in this class at its lowest ISO sensitivity settings, but above ISO 400 the FZ200's noise levels rise somewhat higher, before dropping dramatically at ISO 3200 - not thanks to witchcraft, but noise-reduction, which really kicks in at this point to prevent noise from having too strong an impact on image quality.
As we'd expect, playing with the FZ200's noise-reduction settings has an effect on image quality, with more detail being rendered when NR is turned down, at the expense of slightly more 'gittiness' in midtone areas. With NR turned up, the opposite is true. Some detail is smoothed, but so are midtones, giving better results for low-magnification web or printing. This difference remains consistent at higher ISOs. If you need more detail from your JPEGS, turning NR down may help. But this inevitably comes at the expense of more noise in your pictures.
Raw noise (ACR 7.3 noise reduction set to zero)
In Raw mode, the FZ200 gives higher measured noise than its larger-sensored cousin the LX7, but image quality holds up well alongside competitive cameras. Noise gets more intense the higher up the ISO sensitivity scale you go, but even in this test - where we turn NR down to '0' in ACR - noise only starts to swamp detail at ISO 800 and above. ISO 3200 should be regarded as the final usable ISO setting for anything resembling critical work and ISO 6400 is pretty nasty. We present these samples with no corrections applied, but the FZ200's ISO 6400 output is highly resistant to improvement, unless you need small prints or web output, where heavy luminance and chroma noise reduction won't cause too many issues.