Chris Ross

Massimo, if you are going to point out errors please provide detail on what they are. don't just dump on the author of the article. He is only trying to help provide material for the site. Attacks like this only discourage people from contributing, please in the future think about what you write and how it might impact people.

According to the link I gave, turning the sensitivity down is the path if it gets false positives, but could prove counter productive if it's struggling to realise it's a fish? But definitely try one thing at a time, you could try keep your current settings on one custom function and what you want to try out on another so you can try out both and compare back to back.

Welcome onboard Fred. Whereabouts in Southern Australia do you go?

While Sony does indeed have great AF systems, the documentation is generally woeful and relies upon people spending time with the camera and working how the various choices influence AF behaviour and posting in forums and blogs, YouTube etc. . Add to this the camera is still sort of new (1 year old), UW photography is a small niche in the scheme of things and chasing skittish fish an even smaller segment, and only a % of UW shooters use Sony, means that you are in somewhat unexplored territory. Of course as soon as I hit post someone will chime in specific experience!😂 A logical approach might be try a couple of different combinations and assign them to a custom set and on a dive swap to the alternate set for part of the dive and make notes once you get back to the surface. The biggest community of people relying of good AF tracking is likely to be bird shooters and looking up posts about best AF tracking settings for bird photography will produce some hits for sure. While not directly applicable to your case, they explain how the settings work. For example: https://mirrorlesscomparison.com/stories/sony-a7r-v-bird-photography/#subject This seems to suggest turning up sensitivity IF the camera is not finding a subject. Try finding a few more to give you an idea on the consensus of how the settings behave. You might also experiment with birds as the subject - a perched bird is more like a fish than an animal you might argue - streamlined shape with an eye at one to try to lock onto. Wings and fins are somewhat similar - only different in size. I see you can select multiple subjects in the menu as well and there is an animal/bird option. You haven't mentioned what your experience so far has been. Have you been diving with it and tried pushing the AF system on the subject in question. If you have what has been lacking so far? This may guide you in what questions to ask and settings to play with.

Nice job Davide, always fun to find something rare and even better get great footage of it.

A pelican is good as it is airtight and the gel can bring humidity down to low levels when closed something like 10-20% relative humidity. The humidity will go back to ambient levels of whatever is in the room very quickly after opening the case though.

Silica gel is only useful inside a sealed container, it has limited capacity and moisture will constantly diffuse in from outside unless there is a seal of some type. The fungicide pouches in the link will work for a period until the chemical diffuses away.

The dome has built in extension which you can see here: https://wetpixel.com/forums/index.php?/topic/59042-nauticam-180-optical-gladss-dome-for-sale/&tab=comments#comment-380898 The 43mm is the height of the glass, luckily Massimo has measured the height if the port as 85mm from glass to mount in his post here:

I like things even simpler a light you twist to turn on and twist the other way for off. You don't need anything particularly bright for macro work as you are in close and the AF system doesn't need a huge amount of light. They don't have fancy functions such as red light or off on flash, but with the low power the strobes totally overpower them: I have the INON torches a 330 and a 1400F mounted in their torch holders. Torches: http://www.inon.jp/products/le_light/lineup.html Torch mounts: http://www.inon.jp/products/le_light/acc.html Add a a tall cold shoe mount and you are set: https://www.scubapix.com/essentials/arms-clamps-trays/mounts/25322-long-light-mounting-stem-for-cold-shoe/ I use the supplied diffuser to spread the beam to 60° as it makes aiming them a bit easier. An added bonus is the external o-ring below the head keeps crap out of the o-rings and they basically never need servicing, the only chance for grit or hair to get on the o-rings is when you change batteries and you only need to inspect them.

Courtesy of Massimo: https://drive.google.com/file/d/1o0zId1PZnyGph3_SpVNxU04Z8Ob4So1K/view

It can also grow on the surface of elements, possibly feeding on residual organic matter, enough humidity for long enough can bring it on.

You can calculate all of this from geometry, the radius is published in multiple places as being 110mm, this is outside radius. If you know the radius and actual diameter of the widest part (chord length) you can calculate the the dome height. Previously Massimo advised his was 105mm internal/110external radius and the ID is 170mm. You can use this calculator to do the calculations: https://planetcalc.com/1421/ Scroll down to the complete calculator at bottom and select Radius and chord length (R= 105, C= 170mm) the solution gives the Height of dome as 43mm and the included angle is 108° which is a little more than a 16mm lens on full frame. This means the centre of curvature is 62mm (105 -43 mm) below the bottom of dome element. The included angle is the maximum field of view possible with the entrance pupil at the centre of curvature and 108° is just a little bit more than a 16mm lens which is 106°. This assume that the dome structure doesn't get in the way of seeing the edges of the dome, in practice you may find it's necessary to place the lens a little bit forward to avoid vignetting. In calculating extensions you need to account for any built in extension in the dome itself.

Certainly an interesting lens, though I think a 180mm dome might be a bit optimistic for such a wide field of view. Calculations show that the 180mm dome which is not a full hemisphere has a maximum field of about 108° the same as a 16mm rectilinear lens IIRC, I think Massimo did the measurements and calculations. That means to avoid vignetting the lens needs to sit well forward of the optimum point for the centre of curvature. This would require placing the entrance pupil 60 below the base of the dome, however to have a field of 130° the entrance pupil would need to sit roughly 40mm below the base of the dome. That is getting ahead of ourselves though, first you would need to see how the lens performs on land as things generally don't improve when you put a lens behind a dome.

Thanks Alex, many people seem to be interested in field of view and if the FCP or whatever other wet lens combination would also allow them to shoot more skittish big animals that are often shot with a 16-35 rectilnear with the FCP combination. The horizontal field at 60mm zoom looks like it should be between that achieved by a 20mm up to maybe a 28mm lens, so it should have similar but not quite as much reach but the sharks should look slightly fatter than you might get with a rectilinear lens. So basically a 10-17 lens on steroids.

If you have data on flange position and entrance pupil location that certainly allows you to do the calculations exactly. 60mm certainly seems to agree with what Marelux recommends versus the Nauticam charts based upon comparisons with other combinations. I don't believe it would be close to vignetting with the 20mm lens and 70mm of extension. I have found that manufacturers very often recommend port combinations with significantly less extension than what the precise location of the entrance pupil would indicate. They likely steer well clear of vignetting in most applications as people can easily detect that. That Is why I suggested you try both configurations before you make any decisions or spend money on more extensions. Testing for vignetting on land is merely a precaution which would save you taking the rig UW only to find it was unacceptable. From what I can tell manufacturers make their port and extension recommendations based upon shooting tests with the lens/camera on slide shooting through the dome mounted in a test rig. One example I have is the calculations I did on my 7-14mm panasonic lens in the Zen 170mm dome. I measured the entrance pupil location and did the geometry for field of view at the 7mm end and found the entrance pupil was about 15- 20mm forward of the entrance pupil IIRC. As I understand it too little extension means some barrel distortion which may or may not be acceptable for what you shoot. You may well find 50mm acceptable.

The calculations take care of the non linear change in distortion, what we don't know is what projection it follows. The WACP seems to follow close to stereographic projection while many Fisheye lenses follow Equisolid. The diagonal field could be between 98° and 76° at 60mm on the 28-60 depending upon which projection is followed.

I believe the Zen 170 and Nauticam 180 are very similar, the extension recommendations between those two are identical for most lenses. 70mm may or may not be too much. You can test for vignetting which is the most likely issue with too much extension on land. This test would work if it were a N100 or a N120 extension, but only a N120 extension is compatible with a zoom gear. If you are talking a prime lens though either one could be used I think as the critical thing with a N100 vs N120 is purely the placement of the zoom gear. So if it doesn't vignette you could try it with and without the extra extension to see if you can notice a difference.

Without the port charts coming out and assuming they include the diagonal coverage at short and long ends it's basically guess work. You can do some calculations based upon assumptions to work out what the field of view might be. SO if you assume 180° diagonal and an Equi-solid projection you get this with a comparison to a WACP - from a post of the FCP thread over on wetpixel: If you don't get 180° diagonal with the FCP then the fields will be proportionally narrower all round and if the projection is different (the formula to work out how field changes with focal length ) then the field at the long end will change. This is as good as you will get with current information, hopefully the port charts will show the zoom range when they eventually come out. I wouldn't expect the fields to be hugely different from this. I would though say that the range will be larger than the Tokina 10-17, which is a 1.7x zoom, the 28-60 is a 2.1x zoom. If the wide end is indeed fixed then a higher zoom ratio will give you more reach on max zoom. Likewise the 28-70 would be 2.5x and the Nikon 24-50 would be a 1.8x (28-50 being available.) The problem with the Nikon 28-70 is lack of a solution for a screw drive lens on Nikon Z.

The EMWL is quite heavy, the additional components for Sony weigh 1.8 kg dry, 1.1 kg wet and much of that weight is cantilevered on the flat port with a large twisting moment that needs to resisted. It doesn't strike me as an option for someone who doesn't want to travel with a 230mm dome. My first thoughts for a more manageable setup would be a 140mm dome with a fisheye, but probably not ideal for sharks and mantas but adding a 1.4x times might go close to having enough reach for sharks etc. typical setup have two large floats on long arms for the strobes to hold the nose up. I would think anything with decent current and/or requiring quick maneuvering would prove trying. I'm thinking negative entries in current prone sites might be a significant challenge? The person best qualified to answer is likely to be @Alex_Mustard so hopefully he might chime in.

Hi Colby, welcome aboard and question away!

Which DP-170? You say it's an N85 there are two of them, one with 60mm extension and the other with 30mm IIRC, sounds like you have the one with 30mm extension. Phil Guessed at the right extension being 30mm. The N85-N100 is 20mm long so you would be looking at 50mm total extension with the DP-170 port with 30mm extension built in and the adapter. If it doesn't vignette with that you should be able to use it - albeit living with a possible non -optimal position in the port. If you knew the flange back length of the Sony A7x housing (distance from lens flange to housing surface ) you could do some calculations. An easier way might be to do some port chart comparisons: First up the Nauticam 180 and Zen DP 170 both use the same extension for most lenses in their port charts. Next Marelux include the 20mm f1.8 in their port charts where it uses 50mm extension with their 180mm dome Marelux also list the Sony 16-35f4 Zeiss which requires 40mm extension for same port. Similarly for the 16-35 f4G lens Marelux is 70mm while Nauticam is 80mm extension. The Nauticam system requires 10mm more extension the Marelux system for these lenses. SO for Nauticam the 20mm f1.8 requires 50mm + 10mm = 60mm extension. With the DP-170 N85 port you have 50mm extension. By this comparison it should work OK without vignetting with just the adapter. The port charts suggest you need 10mm more extension, so you could try it with just the adapter and decide if you want to also get the a 10mm extension as well.

A question Phil, you are comparing the light quality with the bare flash, If they both have diffusers like you would if using the 4600K diffusers for blue water wide angle work, is there much difference in light quality?

The best possible solution for snoot use with a Z-330 or Z-240 is probably to use a different strobe I think unless someone develops a snoot with a prism to centre the beam in the snoot.😂 A lot of people add a Backsactter mini flash to their setup rather than try and deal with snooting a strobe with an off centre pilot light. But seriously I don't use the lights on my INONs, they can't illuminate your subject for you as the have a narrow beam, the first rule of UW strobe shooting after all is don't point your strobe at the subject (unless snooting of course).

Thanks Phil, there is indeed some variation, but I think that is a seperate problem if you get into all the possible variations of different manufacturers ports you come up with too large a comparison. On a relative basis (not an absolute basis) you still should be able to compare coverage horizontal differences between a rectilinear and the wet optics. The calculations are mainly to calculate the horizontal coverage from the diagonal. The diagonal coverage can be misleading as the the corners stretch so much due to barrel distortion in fisheye lenses and wet optics. Just to clarify the photos are 28-60 at 28mm for first two and Tamron 28-75 at 28mm for the last and they are all behind a WACP or WWL optic at varying extensions taken from a fixed location in the pool?

Quite likely it will - the Sony 90mm had a reputation for slow focus until cameras like the A1 came out, it seems that the body makes all the difference for the 90mm. Though I don't know that struggles is the right word, the article seems to imply the 50mm was slow but accurate. Here is a thread from WP a while back on the subject: https://wetpixel.com/forums/index.php?/topic/70686-nauticam-a6400-macro-options/&tab=comments#comment-448035 Note that a macro wet lens is not really an option for the 50mm as min focus is so close to the port with just the lens. This I think is the Phil Rudin post you mentioned: https://wetpixel.com/forums/index.php?/topic/67134-sony-a6400-for-macro-and-super-macro/&tab=comments#comment-424189