Ikelite DL 8 Inch dome port vs Compact 8 inch

I’m looking at purchasing an Ikelite housing for my Nikon d850, I’ll be starting with the Tokina 16-28 2.8 FX. Both 8inch dome ports (#75340 & 44) are recommended.

I’ve gone through this article: https://www.ikelite.com/blogs/product-tutorials/when-to-use-a-compact-8-dome-port-underwater?_pos=1&_sid=6ee7d2c52&_ss=r and it seems to favour the compact – 75344 more. I’ll be mainly scuba diving, with some snorkelling too. What I understood is that the main advantage of the larger one is more side sharpness and better half and half shots? Or is there something which I am missing?

Any real life experience with both, which would you suggest? The compact is much lighter and slightly cheaper.

Wide rectilinear lenses are challenging as the corner performance can be pretty poor, you will see lots of threads in the forum with people asking about poor corners with 16mm lenses on full frame.  This is due to the dome port optics the corners of the curved virtual image are not within the depth of field available.  Getting sharp images from a dome port requires two things, the lens entrance pupil needs to be at the centre of the radius of curvature of the dome and the dome needs to be have a big enough radius of curvature to allow the corners to focus.  If the dome is not positioned correctly chromatic abberation and distortion will be introduced.

Ikelite will certainly do the job but there are compromises in that they are built to a price - one of the compromises is the 8"port is the largest available, which is generally considered smaller than optimal for a 16mm rectilinear lens.  You corners won't be fantastic with either dome.  The compact dome port has the additional problem that the centre of curvature will be placed well behind the entrance pupil. Wide angle lenses typically have the entrance pupil close to the front and the centre of curvature of the compact dome will be well behind well down inside the extension.  It needs to be placed well forward to avoid vignetting.

You can't use the S&S correction lens with the Tokina which would help the corners out.  I don't know if you have the lens yet or not, you might consider a 16-35 f4 lens perhaps as it can accept the S&S correction lens.

Generally the recommended configuration to get the best out of a 16-35 lens is a 230mm (9") dome and the S&S correction lens shooting at f11-16 without the S&S and f8-11 range with the S&S.

Fisheye lenses are different and much easier to house  being less sensitive to dome placement and done size. 

Whether corners are important is your choice really and some types of shots like big animals in blue water it is certainly less important.  If you are set on ikelite then I would certainly get the bigger dome.

Totally agree with what Chris has to say. 

My experience with an 8" dome using a 16-35 mm lens on a D800 was pretty awful. The edges were not a pretty sight. It works if the edges of the image contain, say, nothing but blue water - which can be ok for big fish pictures. But if you have elements of a reef included, it just does not look good. You really have to have a  9" dome with a rectilinear lens and a full-frame sensor and even then results aren't always great - hence Chris suggesting the S&S correction lens.

If costs and dome size are important, I'd suggest looking at a fisheye. As Chris says, these are far less demanding and an 8" dome is fine. And they work well for over/unders. I pretty much gave up on the 16-35   and went for a Sigma 15mm which, for many full frame users, is the go-to fisheye lens. I found the combination excellent for divers-on-the-reef shots and for reef scenes generally. One image that you need to handle more carefully with a fisheye is wreck shots. The linear distortions a fisheye can create maybe not what you want in the image. But then they also provide opportunities too!

With a D850 you have a top of the range camera body. It seems a shame to lose the quality that it can produce by compromising on the lens/port combination.

Many thanks for your fantastic advice guys! It's a pity Ikelite haven't taken on this advice! I own the Tokina lens, but listening to your advice I should look into using a different lens to get the most out of the Nikon....I am yet to buy the housing and ports, having said this I'm leaning towards Ikelite as other housings are double its price 

I live in Malta so I will be doing wreck diving frequently, I guess I'll have to get creative! So in your opinion my go to lens should be the 15mm Sigma fisheye? Do you by any chance have an example of the edges with a 16-35? Cheers 

Hey micagius

Sorry, I can't send you examples of 16-35 edges at the moment as I'm travelling for the next 10 days and don't have access to my images. But just search on WP for "soft edges" or some such and you'll find loads. It's an issue that is discussed often.

As I explained, it's not a problem if you have blue water edges. But if you have reef, people or fish away from the centre (hardly unusual), it's pretty horrible, pretty quickly. It sure isn't D850 quality.

If you don't want to go to a 9" port with the necessary EXR, zoom ring and, possibly, in addition the S&S, my advice would be to go with the Sigma 15mm. It's not expensive (as these things go!) and doesn't need port extensions or zoom rings so the whole package is relatively inexpensive.

If you find it doesn't work for you, you could always then think about the 16-35 option which would require all the additional bits and bobs - and you could sell on the Sigma through the Classifieds. They sell quite well. 

Wrecks are typically quoted as an example of where fisheye is not so good as they generally contain straight lines that will be distorted by the fisheye.

The other thing to consider is that just because you already have the camera doesn't mean it's the best solution to take underwater.  I have Canon gear for above water and opted to go with olympus underwater.  I had decided to go aluminium housing and found that i could buy the housing, camera, and lens for less than the price of just the housing for my camera. 

The requirement for dome port size scales with sensor size, for example you could happily use the Nauticam 8.5"acrylic dome with the Nikon 10-24 or 12-24 lens with a D500 or a 170/180/mm/7" dome with a Panasonic 8-18 & GH5.  I expect the Nauticam 8"dome would also be OK but may have some residual corner softness. If the corners are not quite up to standard you could add the S&S lens to the Nikon lenses mentioned. 

Rather than start with the camera look at the overall system camera/lens/housing/ports/strobes/strobe triggering etc.  For example in ikelite housing you are typically restricted to electrically triggered strobes and TTL is probably only available with ikelite strobes, which while they are perfectly fine strobes are very large. 

Are talking classic wreck photography of the wreck itself or shooting things that live in and on the wreck?  that also may make a difference to your choice.