dentrock

Industrial parts suppliers (in Australia anyway) stock a huge range of O rings. Suggest take your old ones in to a bricks and mortar store and have them measured. Industrial replacements may not be made of the same material though. Be sure to test the housing (vacuum or in-water) with the new O rings before risking a camera.

Well if you already own it, no harm in trying. I wouldn't rush out to buy one specially though. I tried a manual fisheye and a Laowa Zero D 9mm (both for APS-C) and found them very difficult to focus accurately. Focus peaking didn't help. Pre-setting the focus is also not great, although it's doable if you know in advance what sort of distances your subjects will be at. First the entire focus range is compressed from infinity to MFD into (say) 25-50cm, depending on the lens. Second (with Nauticam anyway) I couldn't read the focus scale on the lens underwater, and was forced to "convert" land distances to UW distances by making a scale to fix to the housing. All very unsatisfactory.

I have just finished reading your review in UWP. It's a nice summary of your findings within this thread. I second your comments about tolerance for soft corners... but that's a whole other topic. I have marked up July in my calendar to keep it free to devour 121's 'structured testing' of the Laowa lens when it emerges. As the self-appointed guardian of paramount optical quality, he will have much to teach the rest of us plebs. Long may his corners emulate his centres...

There is an interesting article on this very topic, with underwater examples, in the current UWP.

As I already said, lens focuses from about 50mm in front of dome, which is fine for CFWA. Infinity focus no probs too. Enough of your nonsense.

45 EP - 28 (lens flange to housing flange distance) does not give 5-6 ! Check your maths... 45-28=17 required extension. But I am using 25mm adapter (not 35.5) with A7CR which naturally provides 25mm extension.. 25-17 = 8mm excess extension.. But the height of 140 port is 63-64mm with radius of 70mm, so difference is 6-7 which is a required extension. So 8 minus 6-7 gives a mis-alignment of approx 1-2mm excess extension. Pretty darn good. If as you say in the other post, radius is 69mm, alignment is close to perfect! Or in practical terms, no extension required, for this lens, this port and 25mm adapter.....

My measurements are accurate within + or - 2mm. I need the radius to check if a lens with a particular MFD will work with the port, and where the optical centre lies. I don't trust published port diameters. 69 vs 70 makes no difference for this purpose. 63mm (+ or - 2) is top of glass to port flange, a distance necessary to work out required extensions for a particular lens. Would be great if manufacturers made this info available for those of us who want to go 'off piste' from published port charts.

121, it's great that you are guarding the paramount of optical quality! Thanks! (Someone has to do it...) This subject has been covered ad nauseam in previous threads (and on the old site), so I'll be brief: 1. EP for Sony 10-20 is 45mm from lens flange 2. With APS-C Nauticam NA6400 housing, using N85 to N120 34.7mm adapter and N120 140 dome, distance from sensor to dome is approx 129mm. 3. 140 dome is 70mm radius so if you allow say 1 x radius from the dome, you have 199mm. As you say, published MFD for 10-20 is 20cm (200mm) so in practice that means you can focus to approx 70mm from the dome. 4. As I stated, my copy focuses to about 17-18cm for some reason, and I can focus to about 50mm from the dome underwater. Good enough for me, and who wants to squish a subject against their dome anyway? 5. With my newly acquired FF A7RC, distance to dome is approx the same, using a 25 mm N100 to N120 adapter, as the sensor to housing flange distance is longer in the Nauticam A7RC compared to the A6400 housing, by approx 15mm. The above satisfies the useful MFD requirements for a WA lens behind the 140 dome, at least for the Nauticam system. Lenses with MFDs >20cm may work behind the 140 dome, but the resulting underwater MFD is too long to be of interest. This has become a problem (if you want to stick with a small dome) with zooms where the MFD is fine at one end, but too long at the other. The Sigma 18-50 is a perfect example. Regarding the other important parameter (alignment of dome optical centre with lens EP), my measurements using these two setups put the alignment at +3mm for the A6400 rig and -2mm for the A7RC rig, which is as expected. (Minus means the port is to far out by that amount, which can't be fixed and is inconsequential anyway). Now 121, you may not like these conclusions but frankly I'm done arguing about them, and anyway I am reporting my real world experiences, which may not be 'paramount' to some. I'm not suggesting a FF Sony dude rushes out to buy the APS-C 10-20 mm lens, but it's a great option for Sony APS-C shooters. As I already own the lens, I see no reason to replace it with the Tamron 17-28, or in fact the new Sony 16-25, which both require the larger (180) dome. Frankly, given the limited zoom range of these latter two lenses, I would prefer to use a decent closer-focusing wide prime, such as the Sigma 17 or new Laowa 10, if I want to use the full 60 megapixels... or the 20-70 if I could be bothered with the 180 dome (not at the moment).

The Nauticam N120 140 is not a complete hemisphere either. Its radius is 70mm but its height is 63 mm

Couple of other points re Sony 10-20: internal zoom and focus (no extending); minimum focus is around 17cm AF (closer than advertised for some reason); PZ (must be short for painful zoom!) means you can actually zoom it with latest Sony FF bodies (not sure about 6700), although it's clunky. So don't need expensive zoom gear. For my work (mainly small boat and survey work), a rig the size of the 180 port is a no-no and will get smashed. Not to mention I need to be able to tuck it under my arm and write on a slate. I shoot almost everything at ISO 100.

In addition to those, you could consider: 1. Zeiss Touit 50mm macro. It's APS-C but can be used on FF if you can be bothered. Vignetting is reduced to small corners if you change from 3:2 format to 4:3 on your FF cam. However I suspect doing this affects the OIS system if that bothers you. In any case, it's still a great option shooting as a crop lens on FF. It's compact, superb optically, and has internal focus. Updating firmware to V2 is essential. 2. Zeiss 40mm CF. FF lens which focuses to 1:3.3. Also internal focus. Gets a bad rap in the (land) reviews for some weird behaviour up close, but it is also superb optically. Updating firmware to V2 helps. It's currently my go to lens for shooting everything while doing surveys, or anytime I'm unlikely to encounter big stuff. Even then, if big stuff is about, concentrating on head or other detailed pics is always an option. It has one problem - it will tell you things are in focus when you are closer than the minimum distance... when you review the image you see that wasn't so. Solution: familiarity with the lens (back off!). 3. There are a couple of 35mm lenses which go to 1:2. eg Canon; also Tamron. But the Tamron gets universal criticism for poor AF, so that's a deal-breaker for me. The point about these shorter focal length lenses is that with say 60 megapixels, substantial cropping is fine. I can shoot a 25mm goby with my Zeiss 40 and the result is acceptable for publication / ID purposes. If there was a decent 1:2 35mm option for Sony I'd buy it in a heartbeat, as then I could use it with a 140 dome.

For those whose brains don't immediately conflate published focal lengths with FOV, it's 107 to 82 degrees. I had to dig far into the Sony website to find this... While of interest to some, M43 and APS-C shooters will chuckle at reviewers touting this lens as "compact". I'll stick with my Sony 10-20 APS-C shot in crop mode on my A7CR, using a 140 dome. 109 degrees...

Another reduction...! 16mm Nikkor $400 All 4 gears and bayonet converter $300 the lot

Yes, of course wrt min focus. Thanks!

Phil, did you ever test the 20-70 with a 140 FE dome? Any good, or not practical at 20 wrt corner softness (and perhaps not enough room for the lens to extend at 70)?