Chris Ross

It's in the port charts it says you can zoom between 28 and 45mm. Nauticam list the available zoom range for all lenses behind their wet lenses.

It looks like it hits the port at 45mm zoom - possibly more of an issue with the FCP?

It will depend on a lot of things including how bright your trigger source is and what strobe you are trying to trigger. With a mini-flash and an INON strobe I suspect it would be easy. With an LED trigger and a YS-D2 you would probably struggle. I think splitting is probably not going to work and what to do depends upon what problem you are trying to solve. If you have a single fibre port, the twin hole INON bush will allow you to have two cables in one port, BUT if you are using a trigger with this I have seen reports of it not working as the narrow LED beam is not aligned under the cable properly . If you have two strobes at the end of a long cable run, daisy chaining them triggering second strobe off the output of the first would be a good solution. INON also have what they call a wireless connection system - a couple of mirrors to direct light from a trigger into a second strobe: http://www.inon.jp/products/strobe/optical/wireless.html though that probably risks being triggered by other strobes in the area.

Yes but you are restricted to subjects in the 1"(25mm) size range, as soon as you want to shoot say a 4-6"(100-150mm) subject you need to back way off. California is similar in some ways to Sydney, I've dived both, though i Was lucky to get 15m + vis when I was in CA. But in Sydney a long macro lens really does push you towards small subjects. MY 60mm Olympus macro is marginal in Sydney dues to the size range of subjects I get there (120mm full frame equivalent vs 135mm equivalent for the Sony 90mm on APS-C) I guess my point is you can adapt to the conditions but on your home dive sites it'd be nice to be able to shoot a range of subjects without having to wait for a once or twice a year day to shoot bigger subjects.

The 7"dome port is quite big and floaty, I've seen one or two in the field, it may improve things a little but hard to be sure. You could use a 230mm dome, Nauticam probably haven't tested it for Sony APS-C probably because it dwarfs the housing. You just have to work out how much extension to use. As far as the 10-18 performing better if it's not so good topside it can only go one way in a dome UW and that is down (worse). You could also likely use the 7"dome with the 10-20 provided it's long enough, the 7"dome has quite a bit of extension built in. If the 10-20 is the same length or longer than the 10-18 you should be able to use it in the 7"dome, if the 10-20 lens is shorter it would possibly vignette. Regarding the DSC01971 I basically used that of an example of composition which would not work so well with barrel distortion as the straight beam across the top would bow outwards you could correct some or all of it in post processing but you might need to leave space for cropping as the software bends the corners outwards. It certainly seems sharp enough except the far corners. I don't have a feel for how noticeable it would be with a WWL, but a fisheye would certainly show it. Have a look at what the distortion is like with the Canon 8-15 on a door frame here: The WWL would be somewhere between the 8mm and the 15mm view of the door frame, probably slightly closer to the 15mm view than the 8mm view.

The wide range of the 28-80 certainly seems attractive. If you assume the formula for an equisolid angle fisheye is correct the it's interesting that the focal length multiplier for this formula gets smaller as the focal length increases. You have to iterate on the focal length to match Nauticam's fields as reported in the port chart. I usually calculate the horizontal field from the diagonal field to compare between wet optics and rectilinears as the corners stretch more than the horizontal field does, so this means the 35mm end of the 14-35 is closer to a 15mm rectilinear lens, but has the diagonal field of a 12mm rectilinear. At longer focal lengths the difference between horizontal and diagonal fields when comparing this difference is a lot less so just comparing diagonal fields to a rectilinear is close enough.

Welcome onboard Jack, hope you enjoy your retirement.

The dome is not that big when you see it in person and will only get in the way of getting up close to the smallest subjects. I did some comparisons a while back and the Canon 8-15 covers the field of view of an 8mm fisheye and the 7-14 lens, pretty close to 100% of the available fields of view. If you experiment with a fisheye lens the size of subject you can "fill the frame" with reduces dramatically in the last little bit before you touch the dome port and that seems to me to be the advantage of smaller domes. I think subject selection is really the key - it kind of needs to be in a spot where you can approach closely and get the background reef in the frame without close-by objects sticking in from the side and producing weird distorted shapes. I'll probably only really be able to answer the question properly once I try it out.

A 6"dome is really a little small for a rectilinear lens that wide even on APS-C. The 6"dome from Fantasea is not a full 180° dome so the geometry likely means the lens entrance pupil is positioned forward of the dome centre of curvature to avoid vignetting so is not optimal. A bigger dome helps of course but the largest offered by Nauticam is the 180mm dome. You could use the 8.5"acrylic dome and it seems to use 10-15mm more extension than the 180mm dome. Focusing closer has also been mentioned you don't need Manual focus to do that, just use back button focus to focus on something closer in the scene and stopping down to the f11-13 range will also help your corners. As far as distortion goes, all the wet lenses have some level of distortion probably best handled by where you place straight lines in the composition, they bend more as you go towards the corners of course, so for example the image DSC01971 you posted above would have obvious distortion with those straight lines top and bottom of frame.

To be fair though the centre softness goes away when stopped down which you would do anyway behind a dome, the lens is obviously designed with astrophotography and infinity focus in mind so the minimum focus distance is quite long and correction at f1.4 when at MFD not a priority. A rough calculation shows that it could focus at its closest approx 1m from a 140mm dome but in a 230mm dome could focus on an object about 0.2m away from dome surface, so it could be used for reef scenics with a bigger dome. However there is probably little reason to do that when an adapted Canon 8-15 fisheye works as well as it does.

I have used the Zen 100mm dome with 8mm Panasonic fisheye. That lens is very sharp but corners suffer purple fringing (fixable in post). I've just bought a Canon 8-15 and the N85-N120 adapter and looking for the 140mm dome port. The 170mm dome is actually a little small for the 7-14mm lenses (all varieties) and it is has been reported a number if times that they do better in a 100mm dome, both Panasonic and Olympus versions are placed forward of the centre of curvature to avoid vignetting in the Zen 170mm dome. They are really not CFWA candidates. The 12-40 can shoot thing very close in a 170mm dome but to get decent subject size you are zoomed right in so it is CF as as opposed to CFWA. I use the 12-40 a bit around Sydney.

yes, correct, it requires a custom port solution, probably effectively a custom port and housing, though the big opening on the gates housing seems to allow just using a custom port cover with two mini domes.

Apparently Marelux have announced a housing timing not known though: https://www.bluewaterphotostore.com/marelux-sony-a6700-underwater-housing/

We found them easily at Diver's Lodge at Lembeh house reef a few years back, swam down to the spot and they very quickly started spawning.

An APS-C should do fine printing A3. An A3 print at 300 dpi is just over 17 MP while you have 26 MP so you are over sampling by 50%. You'll have more depth of field out an APS_C at same framing as you'll be further back with lower magnification than full frame. Probably a bit optimistic to expect to find a used a6700 housing, so far only a couple of vendors have announced housings for that camera.

I know, but it's still a possibility that something could go wrong and totally agree the leak sentinel is a better option.

This loses at least 50% of the benefit of the vacuum system. Pre loading the o-rings with the vacuum helps them seal at the surface - that's why leaks are so common in the rinse tank. It also assume that you install the plug properly and don't damage its seal when you replace it.

This would be the post, looks like it needs the big port opening of the GAtes housing to fit it in: https://www.facebook.com/thesextonco/posts/pfbid02L4JMoMUUndAhqgVtqoUYWTF6oZ5PMFvfa2VvBce3Ed3Rp1Fd9gB3veDQ4UhmPkCkl And this appears to be the lens with a custom housing for an R5C? https://www.facebook.com/thesextonco/posts/817991040115612?ref=embed_post

Looking at my Nauticam ports the O-ring groove seems to be 1.5mm deep and the o-ring 2.0 mm OD. Getting the gap and groove depth right is the key to compressing the o-ring enough to ensure it seals and also so it won't extrude if the support below the o-ring is insufficient. I would measure and copy what Sea Frogs does with their o-rings. If you have a set of calipers you can measure your existing ports to replicate this on your extension.

If you need to remove the Sea Frogs vacuum system, it defeats much of the benefits of a vacuum system. A vacuum system does two things, it allows you to check for leaks and it pre-loads the o-rings. However, if you need to remove the vacuum valve what happens if the plug you replace it with is not installed properly? Pre-loading the o-rings is important, leaks are most common at the surface when the o-rings are not loaded, it's easy to bump the housing and lose the seal. Far better to have a system that keeps the vacuum on the housing the whole dive. The Leak sentinel is a much better option and is quite popular with people here.

If you want to use a WWL you get the nauticam port and lens combination and change the lug ring over. Regarding your shots, what are you focusing on? Depth of field is 1/3 in front and 2/3 behind your focus point. If you focus on a closer point you may get a little more in focus. Also try shooting at f13/14/16 and compare corner performance. A further option is using a fisheye, you would need the Nikon 8-15 as the the most straight forward option and you could use your existing dome and only buy a different extension ring.

Right, i see how that would help - do you need extra care placing the o-ring compared to the smooth surface of something like an aluminium port? Seems like it might drag a little on the grooves? or does it work out OK in practice?

The bottom ledge looks a little narrow, I would think having it sit flush on top of the ring would be best if the design allows. What is your o-ring cross section? The force pushing the dome and adapter combination into a 90mm ID port is equal to the differential pressure multiplied by the cross sectional area. I calculate the inward force at 40m to be about 250kg. This places the adapter material in compression pushing it inwards so you want to spread this over a reasonable cross sectional area.

That should work, do you need a lip to limit how far it will slide into the extension ring?

Yes sucking the air out is probably a better representation, however as I understand it one of the issues is stability when materials are subject to compression, so for example if you press in lightly on the sides of the can it collapses even more easily. I have never done any 3D printing but it seems to me that the properties of the material are quite dependent upon the way the individual beads of plastic are laid down - does that vary with material and with the type of printer used? I've handled quite a few 3D printed items and they never struck me as something that would readily make an smooth surface to get an o-ring to seal upon. I assume different materials and print setting get around that? On the o-ring groove issue I would think you could make the walls thicker around the groove if needed just by reducing the ID of the port. The Tokina is 70mm OD and your port opening is 90mm - so the you could make the port 100mm OD at the base which would give a 5mm ledge where you insert port into the housing. My o-rings are 2mm OD with a groove ~1.5mm deep, so if you have 5mm wall thickness behind that, the ID would 100-2x(5+2+5) = 76mm ID and the top would be 80mm ID to take your port. You could taper the port out to that ID up at the top potentially. That ID is about equal to the N85 port of the Nauticam ports. Whether 76 mm ID is too small would depend on whether the zoom gear needs to fit through that hole or not. If you don't use mounting lugs and rely upon vacuum to hold the port in you can make the bottom of the o-ring groove a little thicker as well.