It's a pity but there is only two levels when it comes to underwater photography.
You use a GoPro which is simple cheap and takes half assed pictures or you spend thousands of dollars on a proper DSLR and housing plus a dozen other things.
This is demonstrably false. There are plenty of brilliant photos taken with 1" compacts and even smaller sensor cameras such as the old Canon S-series and Olympus TG. I've even seen some macro photos that I simply cannot take with my APS-C ILC due to depth of field limitations.
This seems like one of the more informative posts, but I don't fully follow it. Does "ISO increases" mean a higher ISO or a better (lower number) ISO?
I believe Chris is referring to balancing flash exposure in the foreground with ambient exposure in the background. Basically, if your strobe(s) are struggling to light the foreground, you can increase the ISO, but this will also brighten the background - to cancel that out, you need to increase shutter speed. Imagine that you're shooting a ten-foot sea fan, with blue water in the background. You take a position maybe 4-5 feet away from the fan, set your camera to ISO 100, aperture f/5.6, shutter speed 1/200, dial your strobes to maximum and take a shot. Water is fine, but the sea fan is not. Your strobes are already at maximum, so you need to take in more of their light. You raise the ISO to 200 (one stop), but this overexposes the water. You can stop down to f/8, but this will also affect the foreground, placing you right where you started. Therefore, the solution is to raise the shutter speed to 1/400, which will darken the ambient-lit background but leave the flash-lit foreground as it is. Note that most interchangeable-lens cameras with curtain shutters can only sync strobes at speeds between 1/160 and 1/250, with some being able to manage 1/320 and the recent Sony A1 reaching 1/400 in full-frame mode and 1/500 in APS-C crop. Compact cameras with leaf-type shutters usually don't have this limitation, and Sony RX100 series will happily sync all the way up to 1/2000, although at this speed, you are cutting out a significant amount of strobe light as well.
Thanks, so SeaFrogs gets me $670 for TG6 or or roughly $750 for a G7XIII if I can live with an "Inbuilt leak detection sensor" instead of vacuum. This seems like the best option.
SeaFrogs also makes a G1X housing, is that a good option?
The leak detection sensor tells you that the water is in the housing; by this point, it's usually already too late, so its usefulness is somewhat limited. I don't dive my housing without vacuum, and it has saved me from very expensive incidents numerous times.
I don't know why, but I have never seen or heard about anyone diving with a G1X, or, for that matter, G5X. The G7X series is enormously popular, and I have seen the older G16 used quite a bit, along with the older G9 (without the X) and S-series (S95, S100, S110). G9X is not used underwater for obvious reasons (touchscreen controls), but I don't know what issues with G1X series keep it from widespread underwater use.
Please keep in mind that an underwater camera is a
system, and this system is only as good as its weakest part - when you have a significant bottleneck somewhere, the whole will be
less than the sum of its parts. Getting just the camera and the housing will not produce results much better than your GoPro. Take a look at my Instagram at @bmekler - the first dozen or so images were shot with LEDs or natural light, then cheap SeaFrogs strobes, and the recent stuff I've been posting is with Retra Pros. The camera body is the same throughout.