Domes and Teleconverters: Entrance Pupil ( Nodal Point )

[Adventurer]

Hey @fruehaufsteher2 and @Architeuthis, very glad you chimed in on this and that you are interested so much in the materia.

 

I‘ll try to put this as simple and practical as I can, being a non native speaker:

 

I understood the situation with both of you, is that you abandoned WACP or FCP etc in search for better IQ.

 

Manufacturer portlists (Marelux, Nauticam, Ikelite etc. ) target to a extension ring + dome combination that will give you maximum zoom range / flexibility on that Canon EF 8-15. Mainly because they might not want customers complaining that the dome sunshade or parts of the extension ring are in the picture, because it’s an obvious thing to complain about if you have no clue and just bought expensive glas 😁. The dilemma is that the dome is positioned to close to the lens to archive this flexibility.

A fisheye sees „everything“ which is right in front of the entrance pupil (180 degrees diagonal or even circular). So you must use a full sphere dome. Bummer: none of the Nauticam domes is a real full sphere, like the large Matty Smith domes are… the 140mm dome is missing a tiny fraction in the end which causes a significant offset in the NPP position. This is very practical but does not help your hunt for maximum IQ. I measured and computed this for my 140mm Marelux Fisheye Dome and there you would need a 7.5mm Extension behind the dome for exakt positioning. Nauticam will be very similar to this I suppose. The 140mm dome with Nauticam/Marelux  itself has a small tunnel section of another 7mm, so you can easily see how quickly 1.5cm unwanted offset sneak up on you.

 

Bottom Line: So even the dome you thought which to be a full sphere for your fisheye is not.

As you already own the Teleconverters (TCs) the logic step is to use them to shrink your field of view. Then you can use domes which are not full sphere, such as the medium sized 180mm dome,  @RomiK used for some test shots in this forum.

You can of course also do this with the 140mm dome if you already own it.

 

Next Step: ditch flexibility and abandon the 8mm focal length end -> as a sacrifice for IQ the 15mm zoom end is the preferred operation mode for you. With TC 1.4x you get 21mm focal length. With TC 2.0x you get to 30mm focal length.

Put your metabones adapter / sigma MC 11 plus the Teleconverter and lens on the camera and mount it inside the housing. Measure the distance from housing port flange to the red dot on the Canon EF 8-15mm sunshade. This is the minimum length of the extension ring you will need from Nauticam. I suppose even 7mm to 1cm more because of what I wrote above about the 140mm domes.

 

You will loose some of the wide angle part of this fisheye zoom, as the lens sits now more deep inside the extension ring tunnel. But honestly, would you have used that portion very often underwater?

 

I hope my best practice is comprehensive for you.

If something is unclear just ask.

Edited Tuesday at 08:00 PM by Adventurer

[fruehaufsteher2]

Hi Wolfgang,

 

hey, that’s helpful! 2 ½ weeks sounds great! Wish you the very best! 
 

The MC11 is at half the price of the Metabones and available on site here. That’s what makes me think about it. It’s also less bulky but if it doesn’t fit with the TC… 

So I am REALLY looking forward to your experiences! 

[fruehaufsteher2]

13 minutes ago, Adventurer said:

 

Next Step: ditch flexibility and abandon the 8mm focal length end -> as a sacrifice for IQ the 15mm zoom end is the preferred operation mode for you. With TC 1.4x you get 21mm focal length. With TC 2.0x you get to 30mm focal length.

Put your metabones adapter / sigma MC 11 plus the Teleconverter and lens on the camera and mount it inside the housing. Measure the distance from housing port flange to the red dot on the Canon EF 8-15mm sunshade. This is the minimum length of the extension ring you will need from Nauticam. I suppose even 7mm to 1cm because of what I wrote above about the 140mm domes.

 

You will loose some of the wide angle part of this fisheye zoom, as the lens sits now more deep inside the extension ring tunnel. But honestly, would you have used that portion very often underwater 

As I have some more weeks until we head for our next trip, I‘ll definitely will do exactly that: putting lens, TC and MC11 in the housing and take some measurements. 
In fact I am quite sure not using the circular fisheye-end of the lens very often and therefore the 1,4 TC could be the best compromise. 
 

@Architeuthis I owned the 2,0 TC but sold it due to the weak optical performance… 

Edited Tuesday at 08:10 PM by fruehaufsteher2

[Adventurer]

1 hour ago, fruehaufsteher2 said:

 

@Architeuthis I owned the 2,0 TC but sold it due to the weak optical performance… 

I am curious: was the optical performance on land acceptable for you with the 2.0 TC ? Then you might have sold it too quickly and it was just missing the optical punch by a good sized, well positioned dome underwater 🤔

My guess from the limited unvalidated data donoring in this forum is that you might need 85mm of extensions with the 1.4x TC and 140mm nauticam dome.

 

The slightly larger 180mm Nauticam dome might yield much better results with the 1.4x or 2.0x in the game.

 

[Chris Ross]

4 hours ago, fruehaufsteher2 said:

As I have some more weeks until we head for our next trip, I‘ll definitely will do exactly that: putting lens, TC and MC11 in the housing and take some measurements. 
In fact I am quite sure not using the circular fisheye-end of the lens very often and therefore the 1,4 TC could be the best compromise. 
 

@Architeuthis I owned the 2,0 TC but sold it due to the weak optical performance… 

If you are using the 8-15 with a 1.4x you get a 11.5-21mm fisheye.  The region from 11.5 to about 15mm is unusable effectively as it has big chunks of the corners black and won't do circular of course.  So whatever you do I'd suggest it would be a shame not to have the full 180 deg diagonal fisheye available to you.  

 

Just to be sure you are aware the order is camera-Sony 1.4x- adapter - 8-15 Lens.  This means the nose extension on the SONY 1.4x needs to fit inside the adapter.  It is known it fits inside the Metabones, it probably fits in the MC-11 but it pays to check.  You need someone with an MC-11 to put one on the other to confirm.  

 

This combination (sony 1.4x) needs a custom zoom gear if I'm not mistaken.  The MC-11-Kenko 1.4x-Canon 8-15 has an off the shelf zoom gear available from Nauticam.   There was a post from one of users, Gudge, who poste about this a while back and that will have the details for using the Sony 1.4x, I'm travelling now and don't have time to search.  I think Wolfgang could also advise on the zoom gear.  

 

I'd suggest if you are wanting a WACP substitute zooming will be important and this may be the controlling factor that decides which way to go if time is tight.  I would also suggest that using the standard extension recommendations will be fine, any improvement from fine tuning is going to be in the second or third decimal place.

[fruehaufsteher2]

Hi Chris,

 

I already found out that the Sony TC doesn’t fit into the MC11. So I actually changed my mind and decided to go without TC. 
My current perspective is to use the MC11 and the 140 dome from Nauticam.
 

[RomiK]

1 hour ago, fruehaufsteher2 said:

Hi Chris,

 

I already found out that the Sony TC doesn’t fit into the MC11. So I actually changed my mind and decided to go without TC. 
My current perspective is to use the MC11 and the 140 dome from Nauticam.
 

 

I would encourage you to reconsider. In real world there is no difference between TC and non TC performance (minuscule on charts) and the flexibility of 16-30mm zoom is awesome. In fact and you'd be surprised the main strength of the use of 8-15 vs WACP or WWL1 is its long end.

 

At the short end the results are very comparable except for the angle of view and distortion (fisheye effect). And WACP has greater DOF at CFWA at comparable apertures. But at the long end 28-60 is quite soft and I could not believe what I saw after shooting test charts underwater. 8-15  at 30mm (both 140 and 180 domes) was a real treat compared to 28-60 WWL.  

 

(P.S. @Adventurer - milimeters really don't matter and you need to get wet to find out 😉)

 

And then the money talk. The cost of it all. 1000 (lens used) + 500 (TC) + 500 (Metabones) + 650 (N100/120) + 800 (20+35extensions) + 1000 (the cheaper version of 140mm) + 300 (adapted zoom ring) and I will let you sum it up... Madness. Then 7.5k for FCP solution doesn't sound that bad 🙈😉

 

So from the other angle perhaps  if one wants to tip toe into the world of fisheye and wants to spend close to 3000 for that maybe yes. But I think I bought for friend of mine an entire OMD OM-1 setup with excellent Oly 8mm1.8 and 140mm dome for that amount.

Edited Wednesday at 07:54 AM by RomiK

[fruehaufsteher2]

Hi Romik,

again a new bunch of informations to consider. Good news: I already own the lens and it was really much cheaper and came in "like new" conditions. I own the 1,4 TC (usually use it with the 200-600 if 600 is not enough). The 2,0 TC could be around 300.- but all the other things count.

My personal experience with the long end of the 28-60 is better than yours... maybe quality varies...

 

A lot to think about befor hitting the "buy"-button.

 

Thanks a lot for all the input!

[Chris Ross]

2 hours ago, fruehaufsteher2 said:

Hi Chris,

 

I already found out that the Sony TC doesn’t fit into the MC11. So I actually changed my mind and decided to go without TC. 
My current perspective is to use the MC11 and the 140 dome from Nauticam.
 

To go with a TC you would need about 200 Euro +/- for the Kenko TC, the Nauticam 20mm extension to add on and a zoom gear.  To me it seems quite worthwhile, but only you know your budget.  If you decide to go with a Kenko, make a post here to confirm the correct version.

[RomiK]

1 hour ago, fruehaufsteher2 said:

Hi Romik,

again a new bunch of informations to consider. Good news: I already own the lens and it was really much cheaper and came in "like new" conditions. I own the 1,4 TC (usually use it with the 200-600 if 600 is not enough). The 2,0 TC could be around 300.- but all the other things count.

My personal experience with the long end of the 28-60 is better than yours... maybe quality varies...

 

A lot to think about befor hitting the "buy"-button.

 

Thanks a lot for all the input!

You're welcomed. Comp samples attached with annotation what is what. Details at 100%. As for 28-60 most reviews note the softness at 60 so my thinking is that it is what it is 🤷‍♂️

 

And real kicker is what to think of slapping €6500 FCP in front of 28-60 in long end 🙈. Then all of a sudden the €4500 or so for 8-15 TC2x begins to make sense for the quality overall 🤣

 

Edited Wednesday at 10:01 AM by RomiK

[Architeuthis]

13 hours ago, fruehaufsteher2 said:

 

@Architeuthis I owned the 2,0 TC but sold it due to the weak optical performance… 

 

I think the problem is not the optical quality of the Sony 2x TC, but the optical quality of the lens that is used together with the TC. The resolution/performance of a lens without TC may be o.k., but an excellent 2x TC amplifies the weaknesses of a lens without mercy, if such weakness exists...

 

See e.g. here these test photos of both the Sony 70-200mm lenses (GM f/2.8 II and G f/4 II). At 200mm/f4 both lenses perform nice, but at 400m/f8 when the Sony 2xTC is attached, the IQ of the G f/4 II lens becomes really low, while the GM f/2.8 II is still acceptable:

https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1577&Camera=1538&Sample=0&FLI=5&API=4&LensComp=1662&CameraComp=1538&SampleComp=0&FLIComp=5&APIComp=2

 

It seems to me that the Canon 8-15mm is a high quality lens. IQ becomes a little soft together with the Sony 2x TC. Softness is, however, worse when I use the Canon 8-15mm together with the Kenko 1.4x TC (the non "HD" version). Also IQ of Canon 8-15mm/Sony 2xTC is comparable to WACP-C/28-60mm at the 60mm end (the 28mm end is sharper)...

 

Wolfgang

 

[Adventurer]

On 2/19/2025 at 8:51 AM, RomiK said:

(P.S. @Adventurer - milimeters really don't matter and you need to get wet to find out 😉)

 

The likelihood is very high that my cameras and housings frequently see much more wet salt than yours. 😉

 

You are dead wrong about the mm thing.

Prioritize correct NPP positioning and be amazed.

 

You can lab / pool test this, which is the way to go, before you spend multiple thousand dollars with a dismal travel camera setup in your bag.

[Adventurer]

22 hours ago, Architeuthis said:

worse when I use the Canon 8-15mm together with the Kenko 1.4x TC (the non "HD" version).

That non-HD version has a horrible reputation of crushing your IQ to pieces. I would try to replace that with the new version or the Sony.