How can we test witch lenses a Dome port support?

Is there a way to test (on Land if it is possible) witch lenses a Dome port

support?

I have orderd a Nikon 10.5mm lens with a Dome port from Nexus, FP-120-7.

Now this dome port, have a diameter of 120mm & lengh 45,5mm.

It's exclusive build for the Nikon 10,5mm. It is very compact and that is what I like.

The Nikon 10,5mm is 62,5 mm i lengh and the Dome is build for this.

The Nikon 16mm is 57mm i lengh

The Sigma 15mm is 65mm i lench

So theoretical the Nikon 16mm will fit. Correct?

Is there any way to check it without having the lenses.

Not only if its fit but also if there will be some blooming at the

corner of image. or the image quarity is not good.

Hi Lambis,

I would suggest to take a look at the Nexus website for their list of supported lenses, but not long ago I found out that Nexus does not list all supported lenses in their site. So, my suggestion is for you to contact your dealer, they should know which lenses fit on your port.

Luiz

Luiz

The Nexus webside dont tell mutch. I dealers tell me diferent thinks

The one that is only for the 10.5mm the other that supports the 16mm to and the sigma 15mm No 3 Dealer say that for the sigma 15mm you need a special port

Absolut Chaos

Maybe there are Nexus owners with experience on this

Amazing, I am pretty sure that the Nikons 10.5 and 16 work behind the same port, they are very similar in size and optical chracteristics. Also, they work fine behind the Subal and Sea&Sea fisheye ports. I never tried the Sigma 15mm, let's wait to hear what others have to say about it.

Luiz

The important thing is not so much the physical length of the lens so much as the placement of its optical center in relation to the dome. See the following feature in regard to that subject. In the case of a prime lens its optical center, also referred to as a nodal point is in a more or less fixed position in relation to the external barrel of the lens (it change position a little from minimum focus to infinity) so this can be optimized by the manufacturer either by providing a specific dome port for that lens or inserting the proper extension ring between the dome and housing. How about zoom ?, well they are more complicated since the optical center constantly shift while you are zooming, so there is no dome that will fix that, but the problem is alleviated a lot by using a larger size dome and concentrating on optimizing the wide portion of the lens. Talking to the sales rep or manufacturer will help and dialing in this forum especially will get you first hand expertise from people who use the same product as you do.

http://wetpixel.com/i.php/full/proper-dome...-and-placement/

all this being said, as far as fisheye go, the 16mm and 10.5 should use the same port, the difference in the optical center position (if any) being to little to notice.

Cheers

I am not aware of any manufacturer whose 10.5mm port does not work with 15/16mm fisheyes. So buy the 10.5mm port and I am sure you will be fine.

Try to keep down the number of ports you own as it will save you money and cut down on equipement weight when travelling.

I usually shoot underwater with the following lenses: 10.5mm, 16mm, (12-24mm - new), 17-35mm, 28-70mm, 60mm, 105mm - and I have 2 ports and 1 extention ring.

Alex

Exactly Alex

That is what I whant to do. Keep down the number of ports & save my money for other lenses. Travel light is very important to.

I have now my 10,5mm and I will put a Nikon 16mm or Sigma 15mm

I think that this will owrk with my port .

Then my next lens will be a 60mm or 105mm. Perfect for Under & top photos

On the ned the only that I must do is to test the lens with the port. If it fit and Autofocus work and image quality is O.k. then NO PROBLEMS

And I can do this test on Land or? I dont need to test this on the water

Lambis

The nodal point is not the lens’ centre of perspective and therefore not the reference for placing the dome's center of curvature. The nodal point as reference may apply to rangefinder lenses but SLR wide angles are built retro focus. For example: fisheye’s nodal point is located somewhere in the middle of the lens. Think of placing a dome according to this point. 180° are not captured with a centre at the middle of the lens.

A proper 180° fisheye dome would be a complete hemisphere. But most manufactures offer a compromise and use glass with less than 180° (I don’t say that this is a problem in real life shooting). If you would place the dome according to the dome’s curvature you would capture the port on your images too. Therefore the lens (180° fisheye) has to be placed closer into the dome in order to avoid port vignetting. In real life you can disregard the fisheye lens’ centre of perspective if your manufacture doesn’t offer a true hemisphere. What counts is to place a 180° fisheye just so far into the (non hemispherical) dome that it does not deliver black corners. It is placed to close to the dome anyway in terms of strict optical rules.

In other words: If the Nexus Dome is a non hemispherical one, you can indeed check the length of the lens as fisheyes have their entrance pupil at the top of the lens. But this would not help if you don’t know the default dome distance and extension ring sizes. I would write an email directly to Nexus. They really should answer you which dome for which lens. But I’ll bet there is no problem as the 10.5 and 16mm Nikkors do not differ very much in terms of length. And the Nikkor 16mm offers roughly 70° less coverage. Not such a risk for port vignetting. But better have this confirmed by Nexus.

Zoom: Entrance pupil shift is about 2cm, depending on the lens. Best option is to place the dome for the widest setting. As you zoom in the FOV decreases and corner problems disappear to a high degree. Example Sigma 12-24 on a 1.6 crop camera: maximum shift @24mm. This is equivalent to ~ 38mm. That’s a field of view often used with flat glass. So not to bad if you still use a dome but the placement is off by 2cm. One might expect that not every manufacture is even capable of placing a dome within 2cm tolerance (see the fisheye case, it’s not even possible with some glass). Some more:

http://wetpixel.com/i.php/full/dome-theory/

Regards,

Julian

10.5mm and 16mm with one dome: disregard, Alex was faster

Julian

Is there a way to find the distance from camera bayonett to the top glass element of the lens. For both, 15mm Sigma and 16mm Nikon?