Suggestions for first proper underwater camera?

drusus wrote:

My relative has expressed interest in mirrorless cameras and underwater housings. Do you have any recommendations for a compact entry-level system that is a step up from Olympus TG but will not be a big financial commitment?

Not unless you score a great deal on a used kit. Nothing about underwater photography is cheap.

Camera, lens, housing, optional lights. Or is there such a thing as a digital underwater camera, like a digital Nikonos?

No, dedicated underwater cameras top out on TG-6. There was Nikon AW1, but it was never successful and has been discontinued. Technically there is a digital Nikonos, but you can't get one - in the late 90s, Kodak rebuilt a number of Nikonos RS film SLRs into DSLRs with the addition of a digital back; this was done for the US Navy and has never been available commercially.

One more thing. My relative has the use one one hand instead of two. If there is a system that, for whatever reason, is easier to use one-handed, that would be preferable. Certainly the preference is for a compact system. For example, if lighting is a must (is it?), a light built into the housing would be preferable to a pair of lights on attached arms.

This is not really workable, at least not for wide-angle. Any light located close to the camera will generate significant backscatter - there is a reason why everyone is using arms to carry their lights/strobes. Macro is more forgiving; if you're willing to forgo creative lighting methods (backlighting, inward lighting, etc) you can get away with a single light or a strobe mounted on top a handle without arms.

Another question: ido you have recommendations for an introductory book to underwater photography that I could get her as a gift?

Drusus

Martin Edge, The Underwater Photographer. Alex Mustard, Underwater Photography Masterclass.

Regarding mirrorless cameras - there are many of them on the market now, they can be classified by sensor sizes. There's micro four thirds, represented by Olympus and Panasonic, APS-C, with entries by Sony, Fujifilm, Canon and Nikon, full frame, with offerings from Canon, Nikon, Sony and Panasonic, and medium format that is currently offered only by Fujifilm. Counter-intuitively, medium format is bigger than full-frame, while APS-C is 1.5x smaller than full-frame (half the sensor area), and micro four thirds is 2x smaller (quarter the sensor area). With each jump in sensor size, you need bigger housings, bigger lenses, and most importantly when shooting wide-angle, bigger ports. The 230-250mm domes used by full-frame cameras with wide-angle lenses are truly monstrous, but none of them are small. There are some relative outliers, like the Sony A7C which is remarkably compact for a full-frame camera, or Panasonic GH5/GH6, which are quite chunky for micro four thirds, but I would hesitate to recommend any of them for one-handed use. Bulk aside, I simply cannot imagine manipulating all the controls underwater with just one hand.

One option that might possibly work out for one-handed operation, though, is a housed phone. Kraken/Weefine Smart Housing, SeaLife Sport Diver, Easydive Leo3 Smart, they all feature controls that can, for the most part, be manipulated with just the right hand while keeping hold of the housing. The main weakness of this kind of setup is the inability to sync with strobes. On the other hand, modern phones do a lot of computational photography, and despite the tiny lenses, the output quality tends to be quite decent.