Thank you!! It's like you are reading my mind. I really appreciate the comparison info of the LX100 vis-a-vis the GH4 -- you answered the questions I was thinking about. The video clip is lovely, and those nudibranch pictures are really beautiful!
I'm going to see if I can find an LX100 to hold in my hands, and play with -- to see how I like the handling. If it checks out, then I guess I have Nauticam NEX-5R/T housing and port to try to sell.
This is a really helpful and informative thread. I look forward to seeing more of your pictures (I love that Octopus picture!!!!!!). I'm finding this to be VERY useful!
I have a new iMac (with 5K screen -- I want to get more serious about both photos and video). I took a second look at the Sipadan video I had linked to above, and actually, if you look at some of the less well lit shots, there is a fine grain/noise to them. Actually, there is a grain (if you look hard enough) at the octopus picture, particularly away from the center where the focus is sharp and the colors & detail are very pleasing. Personally, I don't think that that the grain is as noticeable underwater, as it is on land (because there is just lots of "stuff" in the water anyways), but that's just my opinion. My understanding (I don't know from experience), is that if you shoot video in 4k, and then downscale on the computer to 1080p, you will wind up squashing the grain/noise, making it less noticeable.
As I understand it, a micro 4/3 camera (e.g., the GH4, the GX7, or the LX100 --- actually has the GX7's sensor, but it is cropped down a bit because it is multi-aspect....) is that they have inherently greater depth of field than APS-C or Full Frame cameras. So the LX100 has a lens that is F1.7 at the wide end, which is true in terms of exposure -- it lets in F1.7 worth of light on the sensor. But since the sensor is smaller, there is a crop factor, resulting in a greater depth of field -- a bit more than 2X what it is for a full frame camera. So F2.0 on an LX100, would be equal to F4.0 in terms of depth of field for a full frame camera--- so more stuff should be in focus, but would F2.0 in terms of how much light is let in. So (if I have this understood correctly), you actually don't need to stop down the aperture quite as far to get a bigger depth of field, which is a good thing for underwater video/photos (unlike say wedding portraits, where you want that blurry, gauzy shallow depth of field - easier to do with a larger sensor). If the aperture is more open, the hopefully the ISO will drop and the video/photos will be cleaner, or less grainy.
Anyways, I am interested in jumping up to a 4k camera underwater, because I like the idea of shooting all that nice detail (I really LOVE that octopus picture). The options so far are either the GH4 (which has a similar sized sensor, but a lot of really nice video features), the LX100 (smallest size), or the Sony A7s -- which is full frame, has amazing ISO performance, but needs a $2000 HDMI recorder.... too expensive and bulky. If I was a professional, I might go for the GH4, but I am leaning towards the LX100 because seems like a smaller, more manageable sized package underwater, and there is an advantage to small packages. It's also just a lot less expensive. I'm not fully decided yet -- but seeing other people's experience is immensely helpful (Of course, I could get a GoPro -- they shoot 4K, but I really dislike using those cameras. I guess I'm too old-fashioned for those)
Thank you Chris, these are lovely video clips (under some very difficult diving conditions). It seems that the LX100 can really resolve some very sharp detail in video -- because of the 4K sensor readout -- and the colors (when the light is good) are lovely. I'm pretty impressed with what I see so far, it seems like a small, but quite powerful package. It's a few months to my next dive trip, but I may just switch camera systems.
For what it is worth I'm still a big believer in magic filters in video, although I tend to shot reefscapes and larger fish in ambient light (since video lights are just not powerful enough for any distance). I don't tend to shoot as much macro photo/video (where video lights can make a big difference). In my experience with magic filters, you lose a bit of light, but a magic filter + custom white balance at depth can really do wonders to making the colors of the reef really pop. Without a filter, the colors are just washed out, even if you manually white balance constantly. The magic filter really helps -- you can compensate for the light loss with a bit higher ISO, or a bit more open aperture. It just may be trickier to mount a magic filter on an LX100, since it is a fixed lens camera, vs my current setup (a Sony NEX-5R), which is an interchangeable lens camera. But I can figure out a solution in due course.