I have been shooting the D500 since it was released mainly because I have a collection of DX lenses left over from earlier D7000 and D90 and simply the cost. I mainly shoot Fisheye's and I am of the opinion that DX camera perform better than FX in this instance especially when you use the Nikon 10.5mm. The D500 ticks all the boxes which I want it to do at a price which much lower than the FX range.
I use the following on my D500:
I went with the Tokina 100mm as I dont shoot much macro and the Tokina 100mm is a great lens and is half the price of the Nikon 105mm. It does the job for me.
Regarding the battery life of the D500, once changed to the newer nikon battery EN-EL15 Li-ion 20 and turning the camera onto flight mode I was able to get well over 1200 shots for stills. If video was used ther battery life is reduced greatly but I think that is the same for the D850. The D500 has excellent video and custom WB of the fly is great.
I can't comment on the D850 as I have never used one but at the end of the day I think it comes down to you sitting down with your budget and seeing what the best bang for buck. Going for a housing which is made of clear plastic isnt one of them either.
I dont shoot macro very often but when I do its like 3-4 long dives a day for several days and normally in Indonesia. Last trip I bought a Tokina 100mm macro lens and used this for the whole trip and used with the Aquatica close up lense (+5 and +10). The reason why I bought the Tokina was because I didnt want to spend the money on the 105mm when I dont shoot macro often. I was surprised with the quality and performance of the Tokina 100mm macro. The AF was super fast and pin point accurate and there wasnt a need to go manual. There was some very fine rocking back and fro when using the +10 but this was in only a few rare occasions during the trip.
Looks like you have talked yourself into the D500. Also bare in mind that there are other Wide Angle lenses which work very well with the D500 and do not cost a arm and a leg. The Nikkor 10.5mm f2.8 FE is an outstanding lens which can be bought at a reasonable price. If you want rectangular wide angle the Tokina 11-16mm is also a great lens to play with.
Battery life with the D500 is great. But you have to use the new batteries for it. Use the older batteries and there be shorter battery life. This is only an issue if you already have the older batteries from earlier models. If you do Nikon will replace them with the new batteries free of charge. I shoot close to 1000 shots with video over 2 dives and still have maybe 80% battery life.
I also turned off WIFI on my D500 as i found it used battery life as it was searching for a decent WIFI at the dive shop (lots of wifi connections). I turn on airplane mode and never had a problem since.
I noticed on Facebook that Aquatica has a the zoom gear ready and a fellow Australian Matty Smith is going to be shooting the 8-15mm on his D810 over the next few days and interested in how it shoots in the field. Impressed with how quickly housing manufacturers can develop a new product for an item released only a few weeks ago.
As a primary wide angle shooter and shooting in DX I would also like to see how the new 8-15mm compares with the 10.5mm Nikkor FE and Tokina 10-17mm underwater. Most often for me corner sharpness isnt a major requirement when shooting fisheye as often its just negative space with a blue or black ground which doesnt show or need sharpness. Its the quick focusing pin point accuracy on the subject in the middle which is required.
Looking forward to the future indepth review of this lens to see if it has potential for me,
Here are few macro examples taken on a single dive during the week with the Nikon D500 with 60mm Macro and 1.4x Kenko teleconverter. Unfortunately the conditions were better suited to wide angle and local visability had cleared up and lots of Grey Nurse Sharks coming right up to you, but managed to find some interesting macro subjects.
Highlight was finding a large Yellow Kneed Sea Spider.
Late Feb early March is prime summer conditions at Byron Bay. Water temp is around 24-26c and generally its the best time of year for Viz. This time of year we get large numbers of Leopard Sharks (aka Zebra Sharks) and Manta Rays.
I personally would look at travelling to Byron Bay via South West Rocks from Sydney. SWR is about 4-5 hours drive north of Sydney and Byron Bay is another 4-5 hours North of SWR (or 2.5 hours drive south of Brisbane). SWR has Grey Nurse Sharks in numbers and also has a sea cave which is 120m long which goes straight through the island of Fish Rock which is the local dive site. Water temp is about the same as Byron with 24-26c and vis can get up to 40m+. This year they had schooling Hammerheads. This drive will take you through alot of pretty countryside for the non diver and give you the chance to dive a couple of the best dive sites in Australia and gives you more options to choose from if the weather goes bad and not having all your eggs in one basket.
Diving both SWR (with SWR Dive Centre) and in Byron Bay is that the dive shops go out everyday during that time of the year depending on the weather. Alot of other shops on the East Coast do limited week day diving or only weekend.
I think the weight issue is really only for those that need to pack lite for travel. As I do 95% of my shooting locally so I dont need to compromise my setup for size and weight restrictions. When I do travel I have started to travel more smarter with ditching the large pelican case and packing the housing/ports in carry on (Bubble wrapped and in a padded cooler bag) and things like strobes, arms, and rechargers in my check in baggage. Most flights out of Australia these days offer 40kg check in and 7 kg carry on (even on the budget airlines).
I find the weight of a DSLR setup underwater not an issue as I use bouyancy arms and use a 8 inch dome to get a perfectly neutral bouyancy. The the case of the D500 and Aquatica housing I will have to add car wheel stick-on trim weights which they use to balance the wheel to get that perfect weight as at the moment the setup is a fraction positive.
Anders I will weigh my housing on my bathroom scales tomorrow to give you an idea.
Anders I weight my housing with my baggage scales and for the housing alone without viewfinder but with grip handles and vacuum valve weighed 3.39kg (compared with the smaller Ad7000 housing which weighed 2.69kg). The housing with Aquaview viewfinder, 8 inch dome, #18456 extension ring , D500 with Tokina 10-17mm with zoom gear weighed a total of 6.54kg.
Underwater my D500 setup was a fraction more bouyant than the same setup with my D7000. I will need to add wheel trim weights to fine tune.
If your looking at getting new battery packs I suggest the Ikelite Li-Ion packs as they are lighter, quicker to recycle, and hold more charge. The are 3900mAh. The only downside are they take longer to recharge when flat and you have to buy a new recharger as the older Ikelite chargers dont recharge the Li-Ion.
The Ikelite Ds161 movie "video" lights are underpowered and dont have enough width in their beam. The output of the LED "movie" light is 500lumens and is only really suitable for a focusing light for macro stills or possibly macro video. I use two iTorch video pro 6 video lights with my Ikelite Ds161's as they have 2400 lumens, red, and UQ light outputs. I would personally buy the DS160 and used the saved money towards a pair of good video lights instead.
If your doing alot of travelling the Ikelites can be a pain but I prefer them for shooting wideangle which is what I mostly do. On the other hand if your travelling alot and shooting macro I suggest you have a look at the Inon z240 as they are cheaper and much lighter strobe and more suited for macro work. The money you save on the inon's can go towards again a set of good video lights.
I have been using Ikelite DS161"Movie" strobes with my Aquatica AD7000 housing for sometime now. I mainly shoot wide angle and prefer the hard wired Ikelites as they are powerful, have a warmer light output, and I think they are slightly quicker between shots than opitcal fibre connected Inon's Z240's which my friends use. My Ds161's have now had the new Li-Ion battery packs which make the setup slightly lighter but has also increased the amount of shots you can take with a battery pack (often didnt have to change the battery pack for the day). The "Movie" LED light in the Ds161 is a joke and isnt worth using and I use 2x I-torch video pro 6 as my video lights as these little lights pump out 2400 lumens each. I like my DS161 as they are hard wired in and can shoot at 1/320th which you cant with opitcal fibre connected strobes like Inons.
The downside to Ikelite DS161 are:
Cost......they are more expensive to buy new than Inon Z240
Batteries require dedicated battery packs from ikelite and not normal AA batteries for the Inon Z240's
Size and weight of the Ds161 are alot more than the smaller and lighter Z240's which will be an isue if your travelling alot.
cost more to get them optically connected than the Inon Z240's as you have to buy the new opitcal connection for iIkelite strobes.
So Honestly if your doing mainly macro I would suggest the Inon Z240's and a good video light over the Ikelite DS161.
I carry my rig in a cooler bag on the boat and between dives and just after the dives, I dunk my setup in a fresh water tub and press all the buttons. Maybe after a week or two of heavy diving I soak my setup without camera and lens in a tub of warm water with a small amount of white vinegar for a hour or so. After that I dry the housing and use some Silicon spray (hand pump style) and spray into the notches of the control buttons and manually work the buttons. I then pull apart the ports and domes and give everything a good clean and replace any o-rings which look dodgey. After that I vaccum the housing again and leave it over night to double check that I have good seal.
I never leave my rig in a rinse tub on liveaboards and most times I just quick rinse and fold my setup and put in my cooler bag out of the way, in the shade and on the floor so it wont fall if the boat takes one over the front.