Actually, I fully agree with usayit. Whether the test images were taken in low light or bright conditions does not matter, as long as the comparison shots for all of the cameras were taken in the same conditions. This is the ONLY way that you can accurately compare results between cameras.Well.. then the E-P1 is muddier. Just look at the low light shots.
Really? Aren't you trying to convince me that a TX5 isn't as good in low light even though I know otherwise.
Judging by the sample images over at Imaging Resource, the TX5 looks significantly worse than the PL1 even at ISO 800 (which isn't actually that high of an ISO these days). The Sony is applying lots of noise reduction to make the image look less noisy, but the end result is that most fine details are smeared away. The samples were taken in good light, so in actual low-light use the TX5 will be even worse (as there is much more shadow noise that the Sony will smear away with its heavy noise reduction).
Even compared to another small-sensor compact camera (The Canon S95), the Sony still loses out. If you look at ISO 800 samples from both cameras, it's very obvious that Sony is applying tons of noise reduction in an attempt to cover up the noise. Again, the result is that almost no fine details remain (look at the model's shirt, for example).
Below are full-size ISO 800 crops from each camera. It's easy to spot the differences between the TX5 and the others...namely, there is essentially no fine detail left in the TX5 image while there is in all of the others. This comparison proves that despite advances in technology, sensor size is very much still a determining factor in high ISO performance.
Crop from Sony TX5, ISO 800:
Crop from Canon S95, ISO 800:
Crop from Olympus E-PL1, ISO 800:
In addition, the TX5 has another Achilles' heel in terms of low-light performance...its lens. With a maximum aperture of just f/3.6, the Sony'e lens is 1.6 stops slower than the Canon S95's lens, which starts at a fast f/2.0. This means that for a shot you could take at ISO 400 with the Canon, you would need around ISO 1250 with the Sony.
So, in conclusion, not only does the Sony perform worse at the same ISO compared to the Canon S95, but you need a higher ISO in order to get the same exposure due to the slow aperture of the lens. That does not make for a good low-light combination by any means.