Posted 15 July 2013 - 10:54 AM
I believe those videos from Davide are from a hacked GH2 with high bitrate video. It's best to compare apples to apples. I believe Ryan released a video shot with the GH3 in shallow water with the 7-14 and filtered lights not so long ago. It looked good with better DR and noise than the GH2, but it's not really an accurate comparison, due to the depth difference.
With the GH3, I don't suggest using a filter on the lens. The image curves used on the GH3 plus a filter underwater will cause the blue/green channels to clip earlier, creating bigger banding issues. Then there's the loss of 2 stops of light and increased noise.
I don't know the 9-18 Olympus.. The 14-42 is a nice lens but the FOV may be too narrow for the wrecks.
The wrecks @ Bikini Atoll start shallow and then go deeper towards the 50m/160+ range. The atoll can have not so clear sediment filled 20-30m viz which cuts down light. So while the LX7 will work, on wider shots with natural light, the noise will start creeping in at even ISO640, not to mention the drop in dynamic range and resolution as gain is pumped in. Obviously, it's subjective as to what is acceptable quality.
As for night scenes vs daytime for noise levels, not really the same since you are exposing to the lit subjects with artificial light at 3-10ft away, whereas in daytime ambient light shots, one exposes for the entire scene, which is generally lower light, requiring more gain.
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