SeaFrogs A6xxx Salted Line ports comparison

[stewartlife]

I used the hotel pool on my current trip to compare the results of 7Artisans 7.5mm fisheye, Sony 10-18mm and Sony 16-50mm PZ lenses behind SeaFrogs 4", 6" and 8" domes, as well as the bundled wide flat port, attached to the Salted Line A6xxx housing with an A6300 camera and dual SeaFrogs ST-100 strobes. I shot the 10-18mm at 10mm and 18mm focal lengths, and 16-50mm at 16mm, 30mm and 50mm focal lengths, using a range of apertures from wide-open (depending on the lens and focal length) to f/5.6, to f/8 to f/11; didn't stop down past that. All the shots were taken from more or less the same position in the pool - I was sitting down on a bench, elbows braced, camera held just below the surface and center of the frame aimed at floor/wall joint in front of me.

Full results (straight out of camera JPEGs) are here: Port tests

Some personal takeaways:

• Flat port is for surf photography and such, not diving - pincushion distortion ranges from 'that's pretty bad' to 'OMG MY EYES!'.
• 7.5mm fisheye is pretty usable, but at f/8, corners are still a little soft. I need to test f/11 and f/16, but I would need better strobes to light such shots in practice. ST-100 works in TTL-only mode with no compensation when triggered by fiber optics, and this restricts its full output to well below the stated guide number of 32. Waiting for the new Retra Pro to ship.
• At 10mm, 8" dome is maybe a tiny bit sharper than 6" in the corners, but the difference seems quite small.
• Wide-open apertures are pretty useless regardless of port. In low light, ISO noise is still preferable to half the image being smeared.
• 16-50mm fits in the little 4" fisheye dome, and actually works pretty well at 16mm and 30mm when stopped down, but utterly fails to focus at 50mm.
• While the sharpness advantage of 8" dome is minimal, it's more usable for split shots. As far as packing is concerned, 8" takes up a bit more space, but not critically so. I will probably try to sell the 6" dome and keep 4" and 8".

On a different tangent, I finally got my first macro lens - Sony FE 90mm f/2.8 Macro G OSS, right into the deep end, yeah - and I've taken it on four dives over the past two days. Focusing is definitely slower than my 10-18mm or 16-50mm, but not critically slow. On macro subjects with busy backgrounds, it generally takes 2-3 seconds to acquire focus, sometimes a little more. On free-swimming fish, or, in a couple cases so far, turtles, it snapped to the proper focus almost instantly. Working distance with 90mm on 1.5 crop (135mm-equivalent) is very genereous, maybe even a bit excessively so - shooting a small (maybe 30-40cm long) turtle, I ended up out of strobe range while covering only its front half, and could only get its head in the frame while properly lit. One point of note is that it is supremely important to keep the camera still while it's focusing - a bit of current or wave action pushing me around while it's hunting and focusing fails completely. Still, while it has a bit of a reputation of being difficult to use, I found that even for a total newbie to macro photography, getting usable shots was challenging but not impossible.

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Hi @Barmaglot thanks so much for sharing this. I’ve been looking at your reviews and insights on seafrogs salted line housing since last year when i was considering of getting one for my sony a6400, and I found your posts very helpful!

I’ve been using it for almost a year now with the standard port and 16-50 kit lens (I also have the 6” plastic dome, but I rarely bring it for travels due to the size). And now I just got the macro port with 67mm thread as well, as i bought an AOI diopter for macro.

But I’m wondering if you ever compared the standard port vs macro port with 67mm thread underwater? Would using kit lens at its widest at 16mm result in the same field of view? I tested ghis above water and they seem to be the same, but i don’t have access to pool yet hence i’m unable to test this underwater.

Reason being, if both have the same field of view underwater, I’d rather just use the macro port attached all the time (not even bringing the standard port to my next dive trip, saving some luggage space!), and I’ll just use the diopter for macro and take it off underwater if i want something bigger/wider.

Looking forward to your (or anyone’s) thoughts or experience on this. Many thanks in advance!

 

[Barmaglot]

But I’m wondering if you ever compared the standard port vs macro port with 67mm thread underwater? Would using kit lens at its widest at 16mm result in the same field of view? I tested ghis above water and they seem to be the same, but i don’t have access to pool yet hence i’m unable to test this underwater.

It's flat glass vs flat glass, there shouldn't be any difference - both will be equally bad. The threaded port, however, will allow you to attach a wet lens, either a close-up one for macro, or a wide-angle one for, well, wide-angle. I'm currently using the threaded macro port with 16-50mm and Fantasea/AOI UWL-09F and I'm quite happy with the results.

 

[stewartlife]

It's flat glass vs flat glass, there shouldn't be any difference - both will be equally bad. The threaded port, however, will allow you to attach a wet lens, either a close-up one for macro, or a wide-angle one for, well, wide-angle. I'm currently using the threaded macro port with 16-50mm and Fantasea/AOI UWL-09F and I'm quite happy with the results.

@Barmaglot thanks for the explanation!

Speaking of that wet dome you’re using on top of the macro threaded port, did you get any vignetting at 16mm when using the kit lens? Or any trouble focusing on certain focal length?

Cause I was looking at seafrogs 4” wet dome, to be also mounted on top of my macro threaded port. It’s not 6” dome, but I figured it should help in restoring the 25% field of view that is lost on flat port? Plus it seems very compact to travel with as well (which is a big plus for me).

 

[Barmaglot]

Speaking of that wet dome you’re using on top of the macro threaded port, did you get any vignetting at 16mm when using the kit lens? Or any trouble focusing on certain focal length?

I have to zoom in to 19mm to remove corner vignetting, since the UWL-09F is made for a 28mm-equivalent lens. It's a little bit annoying, but no big deal.

Cause I was looking at seafrogs 4” wet dome, to be also mounted on top of my macro threaded port. It’s not 6” dome, but I figured it should help in restoring the 25% field of view that is lost on flat port? Plus it seems very compact to travel with as well (which is a big plus for me).

It can work, but a proper wet lens will let you get a lot closer to stuff.

 

[stewartlife]

I have to zoom in to 19mm to remove corner vignetting, since the UWL-09F is made for a 28mm-equivalent lens. It's a little bit annoying, but no big deal.

@Barmaglot And that 19mm with macro port + wet dome is still larger field of view than you would have on 16mm with just macro port?

 

[Barmaglot]

@Barmaglot And that 19mm with macro port + wet dome is still larger field of view than you would have on 16mm with just macro port?

I should make myself more clear - the 19mm applies to usage with an actual wet lens, such as AOI / Fantasea UWL-09F or Nauticam WWL-1. I believe Weefine WFL-01 will work at 16mm, as it is designed for 24mm-equivalent lenses, but I have not tested it. Regardless, all of those will give you a 130-degree diagonal field of view. 16mm on APS-C by itself gives 84 degrees, and a flat port underwater shrinks that to about 60. A dome, whether dry or wet, will restore those 84 degrees, but nothing more.

 

[stewartlife]

I should make myself more clear - the 19mm applies to usage with an actual wet lens, such as AOI / Fantasea UWL-09F or Nauticam WWL-1. I believe Weefine WFL-01 will work at 16mm, as it is designed for 24mm-equivalent lenses, but I have not tested it. Regardless, all of those will give you a 130-degree diagonal field of view. 16mm on APS-C by itself gives 84 degrees, and a flat port underwater shrinks that to about 60. A dome, whether dry or wet, will restore those 84 degrees, but nothing more.

Hello, I understand that part. What I’m wondering is, which one is larger field of view:
1) 16mm with just macro port >> which say 60% of 84 degree = ~50 degree
2) 19mm with macro port + your dome combo >> 100% of what degree?

To see whether than it makes more sense to just stay with the flat macro port without dome, if there’s no benefit on the field of view (due to the vignetting caused by your Fantasea-AOI UWL-09F)

 

[Barmaglot]

19mm + UWL-09F/WWL-1 gives you a 130 degree diagonal field of view; considerably wider than even a 10mm rectilinear lens in a dome, albeit at a cost of significant barrel distortion. It is not as wide as a true fisheye, but it's close.