I wanted to share a 4 inch dome build.
My housing is a hugyfot D7000. A recent second hand purchase that came with a 7 inch dome. If anyone has fitted a D7500 in a D7000 housing I'd be very interested to hear! May be a future project for me and looks possible - better fit than a D7200.
I was able to use a 4 inch ROV dome and an extension ring to build a dome port. Cost all in was circa £60 and I have also purchased two spare domes -£15 each. 5 min change.
I'm very pleased with the result and have dived to 30M + with no issues and am very confident it will be fine to 50M.
I'm using with a tokina 10-17mm lens and results look to be good - I just need to practice my CFWA - strobe placement is my challenge at the mo.
ROV dome port - ref 1Set Optical PC Dome Cover 110 Dome Cover Underwater Robot Camera Dome Cover 1000 Withstand Voltage|Parts & Accessories| - AliExpress
Hood ref 49mm 52mm 55mm 58mm 62mm 67mm 72mm 77mm Screwed Flower Petal Sunshade Lens Hood For Nikon Canon Sony Fuji Olympus DSLR Camera|Camera Lens Hood| - AliExpress
the 82MM one - need to saw off the threaded area.
This is dome is claimed to be OK to 1000M! I'm happy with the quality.
Extension ring - I cut down a surplus ring I got with my second hand housing. made sure the tokina 10-17mm got close - within a few mm of the dome.
Cut the extension ring with a hacksaw to the required length. the extension rings from Hugyfot taper inside which is helpful when forming the aquasure gasket seal.
Machine down the inner diameter of the extension ring. Not too thin.
Cut the ROV dome ring - in my case about the position of the upper o ring.
File the remaining ROV alloy down to fit inside the extension ring. Power file was used for all this work.
Fit the ROV port into the extension ring I used aquasure to form a permanent gasket. I had a tight fit but the glue filled the voids and taper area so i was confident in a air/water tight gasket.
Use marine epoxy to produce a strong ring at the top of the join with the extension ring.
Use marine epoxy to form a strong filler bead in the inside edge.
All in this gives 3 layers of protection/seal. You may have the ability to do a build that keeps the ROV port gasket but I did not manage that.
I adapted a hood - had to drill slight indents so that the bolts can still be accessed for dome change if needed. Had to cut all fins. Glued into position with marine epoxy JB weld..
Made some small fins to retain a lens cover in the water - cut plastic and screwed into the ROV 'ears' see description - Type 3 ROV dome assy purchased.
Before the hood was fitted
Hope this of interest.
For my second hand SLR this was a cost effective option to get a 4 inch dome port.
I guess a similar build would be possible with other housings.
Wish I had taken more in progress shots.