Trying to get the length measurement of the metabones adapter for Canon EF-S lens to Sony camera, all in an effort to find a working Seafrogs dome setup for the Canon 8-15 F4 fisheye.

 

Anyone can share the actual measurement as it adds to the lens length?

 

Or share some experiences with Sony, Seafrog and the Canon fisheye?

 

Thanks

 

Ole

 

EF mount flange focal distance is 44mm, whereas E mount is 18mm, so the Metabones adapter fills the difference at 26mm.

I measured mine and It is exactly 26mm, as Barmaglot pointed out.

 

What I am now curious about, is why the Nauticam N100-N120 adapter is 35,5mm and is somehow supposed to use the same ports.

 

2 minutes ago, Robin.snapshots said:

I measured mine and It is exactly 26mm, as Barmaglot pointed out.

 

What I am now curious about, is why the Nauticam N100-N120 adapter is 35,5mm and is somehow supposed to use the same ports.

 

 

 

When the camera is attached into the Nauticam housing the distance of the sensor to the opening in the housing, whre the (dome)ports are attached is different between Nauticam housings for Sony and for Canon DSLR (EF mount). The Nauticam adapter compensates for both the Metabones adapter and the additional distance of Canon DSLR housings...

=> Beware, these distance differences between Sony and Canon DSLR housings may be different for Seafrog housings...

 

Wolfgang

I just looked through various Nauticam port charts, and it appears that the 8-15mm is gone from most of them - weird. 

 

Isotta is more helpful though. For Sony cameras with Canon 8-15mm, they spec a 40mm extension for bare lens, and 60mm for lens + TC. They also spec a 50mm extension for Sony 28mm prime with fisheye converter. Other wide-angle lenses, like the various flavors of Sony 16-35mm require longer extensions. On the SeaFrogs side, 8" dome port V.8 lists 28mm f/2 with fisheye converter as compatible, so it is probably close to Isotta's 50mm extension in terms of dome positioning, while V.9 and V.10 target various 16-35mm lenses and are likely too long. It's very unlikely to be an exact match, but it's probably in the ballpark. Fisheye lenses are generally somewhat tolerant of slight misalignments in dome positioning, so a bare 8-15mm has a good chance of working with it, but if the extension is slightly too long, it may vignette. If it does, then adding a teleconverter (make sure to use the latest version from Kenko) should lengthen the lens enough to get rid of the vignetting and give you a useful zoom range. In any case, you will most likely have to make your own zoom gear, as SeaFrogs support the Nikon 8-15mm (with Z6/Z7 housings) but not the Canon one. If you want, I can share a zoom gear that I made for Tokina 10-17mm on SeaFrogs A6700 in TinkerCAD - it should be the same as their plastic A7 series housings on the gear engagement side; you just need to tweak the height and internal diameter to fit the Canon 8-15mm.

 

Edit: On the other hand, the SeaFrogs V.8 dome is also listed as compatible with Sony 10-18mm APS-C lens, which, on Isotta's charts, is listed as needing just 20mm of extension, which gives you an idea of SeaFeogs' level of precision there. Still, if the extension is too short, with a fisheye lens you might not even notice, and if it does become an issue, you can add a 23mm extension ring. 

Edited April 5, 20241 yr by Barmaglot

20 hours ago, Barmaglot said:

I just looked through various Nauticam port charts, and it appears that the 8-15mm is gone from most of them - weird. 

 

It seems all fisheye options are removed. I remember the 8-15 being 30mm extension + 140mm dome on N120 but please correct me if I am wrong. 

 

 

20 hours ago, Barmaglot said:

Edit: On the other hand, the SeaFrogs V.8 dome is also listed as compatible with Sony 10-18mm APS-C lens, which, on Isotta's charts, is listed as needing just 20mm of extension, which gives you an idea of SeaFeogs' level of precision there. Still, if the extension is too short, with a fisheye lens you might not even notice, and if it does become an issue, you can add a 23mm extension ring. 

I wouldn't trust the seafrogs port charts for any useful information to be honest. Unless they recently moved to better testing their criterium for the lens chart is more or less "fits inside".  I bought a lens/port combination that was on their port charts a couple years back that turned out completely useless as it wouldn't focus.

25 minutes ago, Robin.snapshots said:

I wouldn't trust the seafrogs port charts for any useful information to be honest. Unless they recently moved to better testing their criterium for the lens chart is more or less "fits inside".  I bought a lens/port combination that was on their port charts a couple years back that turned out completely useless as it wouldn't focus.

They do seem to at least test for vignetting, as in some cases they note focal length limitation, but otherwise, yeah, they're not too concerned with proper lens positioning. Still, for a 180 degree fisheye lens, using a hemispherical dome, 'edge of vignetting' is pretty much the proper positioning.

 

What exactly did you use that wouldn't focus at all? The only thing I've run into even remotely similar is 16-50mm lens with 4" dome - it works at shorter focal lengths, but fails to focus when zoomed in, as the dome is too small; the virtual image that it generates is too close for the camera for the lens to focus when using a longer focal length. Did you try to use a lens with a long minimum focus distance behind a similarly small dome?

2 minutes ago, Barmaglot said:

What exactly did you use that wouldn't focus at all? The only thing I've run into even remotely similar is 16-50mm lens with 4" dome - it works at shorter focal lengths, but fails to focus when zoomed in, as the dome is too small; the virtual image that it generates is too close for the camera for the lens to focus when using a longer focal length. Did you try to use a lens with a long minimum focus distance behind a similarly small dome?

I was using a Samyang 8mm f2.8 fisheye ii on my a6400 salted line for which I purchased the 4" dome and focus gear specifically.  I suspect indeed the minimum focus distance was the issue here which was quite disappointing at the time.

 

Some lenses on the charts also seem to be geared towards surf photography instead of uw  i.e. long telephoto lenses 

Huh, that's odd... I've used a 7Artisans 7.5mm fisheye with the same dome, and while focusing was somewhat annoying (I padded out the focus ring with double-sided tape and used a 16-50mm zoom gear to focus), it was possible. Looking at specs, now, yeah... the 7Artisans 7.5mm lens is listed with 15cm minimum focus distance, whereas Samyang 8mm specs 30cm - that can certainly impair its function in small domes. Being a fisheye lens, you can't use a diopter either. Obviously no one has tested it in water before offering it for sale, although it might be okay for surf photography uses.

 

Still not as silly as the optical bulkheads on their FX30 housing though.

Edited April 6, 20241 yr by Barmaglot

1 hour ago, Robin.snapshots said:

It seems all fisheye options are removed. I remember the 8-15 being 30mm extension + 140mm dome on N120 but please correct me if I am wrong. 

 

 

I wouldn't trust the seafrogs port charts for any useful information to be honest. Unless they recently moved to better testing their criterium for the lens chart is more or less "fits inside".  I bought a lens/port combination that was on their port charts a couple years back that turned out completely useless as it wouldn't focus.

Yes that is correct, the 8-15 used a 30mm extension with the 140mm dome, I have an old version of the Canon EF port chart open in my browser now. 

 

I also opened the new one and it is now one long page instead of being divided into pages like the old one and cuts off suddenly in the middle of page 7 of 9 and the listing for the Sigma 14-24 is cut in half.  Seems like the obversion to pdf might have failed somehow and it cuts off a few Zeiss lenses, the Tokina 10-17, Nikon 10mm  as well as the 8-15 fisheyes and the Sigma fisheye.