Salted Line/Sony a6300/Sony 18-105mm f:4.0

[dkjens0705]

Been using a Sony a6000 with 16-50mm kit lens in Meikon housing with wet macro lenses but unfortunately flooded it. I really want to now upgrade to SL housing, a6300/6400, 18-105mm f:4.0 lens but the suitable flat port does not have the 67mm thread for external wet macro lens mounting. SeaFrogs doesn't answer when asking what outside diameter of port is and is no help. Does anybody here use that housing/port/lens for macro photography and if so, which adapter for diopter attachment do you use?

 

[Pyndle]

I don't know if you've already made your purchase but I saw this review, where the guy was basically saying his 18-105 wasn't compatible with the dome (even though seafrogs says it is):

 

[dkjens0705]

Thank you for the post, that's an interesting problem. I don't care about the 18105 working with a dome port but if it has the same problem with a flat port, well that would be no good.
I have not made the purchase yet, just replaced my flooded a6000 and 1650 kit lens so far.

 

[Pyndle]

Got ya. Worth checking with the flat port (and don't trust what Sea Frogs says, those guys don't have a clue).

 

[Barmaglot]

SeaFrogs' definition of compatibility is, unfortunately 'it fits in the port and does not vignette'. What's happening here is that the Sony 18-105mm has a minimum focus distance of 45cm (1.5 feet), while the Sigma 16mm has 25cm (10 inches). A dome port placed underwater acts as an additional lens element, forming a so-called virtual image at 3x the dome's radius from its center, which is what the lens needs to focus on. Between the six-inch dome that the guy had mounted, and the lenses 45cm minimal distance, the virtual image ended up being too close to focus on - that's why it worked for him in air but failed in the water.

This was actually a very common problem back in the film era, as back then, most lenses had fairly long minimal focus distances. Most modern lenses can focus at 25-30cm, so it isn't much of a problem anymore, but the Sony 18-105mm is an outlier there. The typical solution for this problem, back in the old days, was to place a +2 or +4 diopter on the lens, which would bring down its minimum focus distance - it may work on 18-105mm, or it may not, I'm not sure. A larger diameter dome (not the same as a larger size, as most domes are a section of a sphere, not simply a hemisphere) alleviates this to a degree, but I haven't measured the curvature radius of SeaFrogs six-inch and eight-inch domes (I probably should, as I happen to own both).

Flat ports don't suffer from this problem, but they introduce distortion at wide angles. In general, the 18-105mm is not a good lens for shooting underwater, mainly due to its long minimum focus distance and housing difficulties. Neither Nauticam, nor Aquatica nor Ikelite feature it in their port charts (Ikelite does, technically, with a 'no port recommendation available'). If you want to shoot wet lenses, stick to 16-50mm and the short macro port. The SeaFrogs solution of 18-105mm in a flat port is targeting surf photography rather than diving.

 

[Pyndle]

Wow, you're so knowledgeable Barmaglot!!
By any chance do you know if the new 16-55 F2.8 lens would fit in any of the sea frogs housings? (they told me that it doesn't and that they don't plan to make an update to their ports but wondered if someone actually tried)

 

[Barmaglot]

The 16-55mm f/2.8 is very new, and I haven't seen any mentions of anyone trying it underwater so far, much less in a SeaFrogs housing - the Venn diagram of 'people buying $1400 lenses' and 'people buying $300 housings' has very little overlap.
In theory, it could be housed behind a dome, similar to the 16-70mm f/4 Zeiss, and its diameter is sufficiently small to fit into the Salted Line housing while leaving space for a zoom gear - it's 73mm in diameter compared to 10-18mm's 70mm - but you'd need to design and 3D print your own zoom gear, and dome positioning can be a big problem.
Basically, to properly function inside a dome, the lenses entrance pupil needs to be placed at the geometric center of the dome (i.e. the full sphere that the dome is a part of). This is the reason that Nauticam et al offer a variety of extension rings for their ports - they test various combinations of cameras, lenses and ports by moving the camera back and forth on rails while photographing test charts, then evaluate the results and determine the optimal extension.
Coming back to the Sony 16-55mm f/2.8, there are three big issues:

1. SeaFrogs/Meikon does not sell port extension rings. Their six-inch and eight-inch domes come with a built-in extension that is engineered to, more or less, match the entrance pupil location of the 10-18mm and 16-50mm lenses, but 16-55mm is a completely different beast.
2. The entrance pupil moves as you zoom, so the extension that works at 16mm won't be what you need at 50mm. It's not much of a problem with 16-50mm, as it zooms internally, and since it is so tiny, the entrance pupil doesn't have much space to move. 10-18mm extends to zoom (funnily enough, it extends to zoom out), but the distance is very short - less than a centimeter. 16-70mm also extends to zoom, but not too much, so it works in a decent-size dome. The 16-55mm, however, is long to begin with, and it extends a lot, so obtaining a good image across its focal range while in a dome may turn out to be physically impossible.
3. If you give up on a dome and decide to use a flat port, the extending design bites you again - the port needs to be pretty long to accommodate its full extension, which means that at 16mm, it will be sitting way deep inside, requiring a very large diameter glass to avoid vignetting, and completely precluding the use of wet wide lenses.

Finally, the f/2.8 aperture is very situational underwater. The only place I've been to (although, full disclosure, I'm speaking from the height of experience that is 150 dives over 2.5 years) where it would come in useful is Monad Shoal off Malapascua, Philippines - 30 meters depth at 6 AM, fast-moving thresher sharks with blue water around them so you don't really care about corner sharpness, and all artificial light is strictly forbidden, so you need fast shutter speeds in dim light. Anywhere else, there are lenses more suitable to underwater photography than the 16-55mm f/2.8, and even there, the Sigma 30mm f/1.4 ($289 new) is probably the better choice. Anywhere I can shoot with strobes, I use f/8 or smaller anyway.

 

[Pyndle]

Haha I agree with your first sentence. I'm one of these weirdos with very expensive lenses but cheap underwater gear - underwater photography is not my main focus, it's just a nice to have when I go diving on my travels so I don't want 5k usd of gear, but I don't mind having 10k usd of lenses and flashes for above water

And since I already have the 16-55 and it's much sharper than the 16-50kit, I thought It'd be good to use it. Tbh the F2.8 can be useful for certain shots in cave and wreck diving as well but agreed it's not worth all the hassle you described. Especially since I'm not willing to give up my wet dome setup: there is no way I'll ever go in the water with a setup that can only do wide or macro (ok maybe a full macro setup in lembeh but that's it). I want a zoom lens, flat port, and will always carry my wet dome AND diopter so I can change on the go

 

[Marshmellow]

I'm actually considering using the Sony 16-55 in a Nauticam NA-6500 housing as an improved single dive travel rig . I have used the Kit S18-55 and S16-70 in a N85-4.33 FE port with extensions and a custom zoom gear. The Z16-70 has close to the same lens extension distance as the new S16-55: 40mm. My calculations show S16-55 lens will come close to working with 100mm of extension in the small N120-4.33 port. While the calculations look possible, I won't know for sure until I gather the components and test the optics and mechanics. This will require the N85 to N120 50mm port adapter and 50mm N120 ring extension for the needed 100mm of extension, the N120 4.33 dome and T10-17 zoom gear adapted to the S16-55.

Currently I use the S18-55 kit with a modified N85 4.33 FE dome that has a diopter swing mount added to it's shade. I strictly use this set-up for a small and light travel rig when I want moderate WA, CFWA, and SM on the same dive using one lens, a CMC-1 wet diopter and single 4.33 port w/ ring extensions. I can also use my Z12 with this set-up for better CFWA and wider FOV. This will require me to transfer the swing mount to the N120 4.33 shades and hopefully use the S16-55 for it's much higher IQ and video with it's constant aperture, not to mention it's 2mm wider FOV. By adding a 20mm N120 extension to the set-up, it will be configured for the popular T10-17 FE lens, which I like when I was a Canon guy.

Not sure this is all worth it, since my N85 set-up works well with the S18-55 kit and the extra needed equipment is expensive, but I've read that the IQ on the S16-55 is considerably sharper than the S18-55 kit from corner to corner. It would be great to do much sharper WA, CFWA and SM that somewhat compares to my S90 and Z12 set-up. All the lens I currently use in my N85 4.33 port set-up should work the same in the N120-4.33. While the 4.33 is a FE dome, I find the slightly perceptable softer corners with the rectilinear lens acceptable compared to the much larger domes. Nor would I be able to graft a diopter swing mount onto their shades for SM.

 

[dkjens0705]

Wow, lots of information here, much of it way over my head ha ha. Where I do my diving (mostly Kata Beach, Phuket, Thailand), I look for macro and the occasional octopus, mimic when lucky. I've come to the conclusion that I really don't like pushing a huge rig around and it can be very hard to get a big dual strobe rig close enough to really small nudis for a decent photo. Sometimes though I would like to take a photo only using ambient light and WB adjustment but so far have been able to find a way of doing that once the camera flash has been popped up.

So my question here is, is there a setting on the a6000 where, with the flash popped up, it is possible to turn the flash off AND adjust WB to a custom setting? I find that only one or the other is possible but I hope I've missed a way to do it.