Some interesting findings on Nauticam Water Contact Optics on Sony

I have been playing with the WWL-1 and with the prototype WACP, I have also received several photos from other users here of their gear WACP-C and WACP-1 and I have to admit I am rather suprised

The first assumption that I had made and perhaps other people have made too was that a dry mount would mean that the rear element of the lens was closer to the adapter compared to a wet mount

This has proven wrong an all accounts. Comparing the Sony 28-60mm with flat port 45 and WWL-1 shows that on average the wet mount means that the lens is closer to the wet lens despite the port we are talking about less than 5mm

With the WACP-C and 30mm extension the front of the Sony 28-60mm is over 1 cm away from the rear of the optic.

With the WACP-1 on N100 mount the situation is similar to the WACP-C and if you use the N120 mount with the 35mm extension the lens is actually further away 5mm. Interestigly Nauticam puts the * for best performance on the N100 mount

The other assumption that I had was that the dry mount would be more effective in terms of contrast and flare because it is dry. However with the Sony 28-60mm lens and the gap between master and water lens there is possibility of bouncing light. In addition the lens is very small compared to the port so there is a lot of space to have light rays scattering around. Does this explain why the WACP-C flares more? Not sure but it is something to test

The final assumption I had was that the field of view would be the same. That is also not true, although the lenses have the same 0.36x magnification the WWL-1 sits closer to the lens than the WACP-C and the WACP-1 with N120 mount further away. So it seems like the field of view of the WWL-1

I have some questions in my mind that I would like to have an aswer to

1. Why is nauticam not making a 20mm N100 extension ring so that the 28-60mm sits right on the glass?

2. Is the gap intentional or just a concidence due to the fact the  wet lenses are generic not specific to a lens?

3. Should I work to get my lens closer to the back of the glass or not? Common sense say yes, this would reduce vignetting and improve contrast reducing aberrations at the edges but maybe I am missing something here?

I know the answers are not in the forum but would welcome opionions from users of those lenses

I would think the spacing to the rear element of the lens would be set by geometry.  Once you design the lens be it a WWL or a WACP type the exit pupil diameter of that lens would then set the spacing to a lens with a 28mm field of view as the light cone shape is set by the lens focal length.

I recall reading that the WACP lenses had progressively larger rear elements so it would make sense this would be accompanied by a larger exit pupil which would require larger spacings as the size of the exit pupil became larger if the camera lens remained at a 28mm field of view..  The spacings would decrease as the focal length was reduced with a corresponding larger angle of view.

I would think the spacing to the rear element of the lens would be set by geometry.  Once you design the lens be it a WWL or a WACP type the exit pupil diameter of that lens would then set the spacing to a lens with a 28mm field of view as the light cone shape is set by the lens focal length.

I recall reading that the WACP lenses had progressively larger rear elements so it would make sense this would be accompanied by a larger exit pupil which would require larger spacings as the size of the exit pupil became larger if the camera lens remained at a 28mm field of view..  The spacings would decrease as the focal length was reduced with a corresponding larger angle of view.

Not sure I can align on this

The lens entrance pupil is what gets the light inside the lens the lens exit pupil is what sends the lens to the sensor

The diameter of the overall lens is mostly influenced by the focal length and the physical maximum aperture which is normally achieved when the lens is zoomed

The diameter of the glass in front is driven by those considerations

If a lens is fast like a 28-70 f2.8 the distance from the wet lens is a compromise with mechanical vignetting that happens as you move the wet lens away

For the small kit lenses like the sony 28-60 or nikon 28-70 those lenses are so small and have such a tiny aperture that will vignette very far away from the lens even if the infinity field of view is still the same

For those lenses that don’t really extend when zooming you have a choice if you put them close to the rear of the wet lens or further away

Nauticam has told me that they go through the various extensions they have and compare results if those are good they don’t go and create a new extension ring

We have had a case with the nikon 28-70mm and the wacp-c where the extension of 30mm would vignette so they had to make ad hoc a shorter one for that lens

In simple term a slower lens will always be smaller of a larger lens at equal zoom range example sony 28-70 55mm filter size vs sigma 28-70 67mm filter size

This means the sony 28-70 will vignette less and due to the construction (the lens is longer at 28mm) will preserve the entire zoom range

This lens uses the extension ring 50 and adding the 25mm inside the WACP-C has a gap of 5mm from the front of the lens

Performance is adequate full zoom range is supported -> no need for custom 45 extension

Now look at sony 28-60mm this lens has an even smaller physical aperture and again the lens is built in such a way that at 28mm is 1mm less in length than it is at 60mm

Nauticam goes for the shortest 30 extension the lens has a gap of 1cm performance is good no vignetting-> no custom extension to be made

Same lens with wacp-1 N120 has a gap of 1.5 cm so it doesn’t get the * of best performance that goes to the shorter N100 mount with 30 extension

In summary i think this is more a case or working with what they have and selecting the extensions they have and checking performance instead of starting green field for each lens

So for me this doesn’t conclude at all that a gap is required to improve performance it is just a consequence of the constraints set and the way the lens is built

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You should just get yourself a macro slide and a larger container and test this. All this speculation is leading nowhere. I agree that having a gap there seems counterintuitive, but Nauticam tests so many setups, I can't imagine they didn't notice and came to the same conclusions. 

It is worth commenting that with lens designs, their quoted focal length range is at infinity focus. Some modern lenses may well use internal focus/zoom optical components which, when operated, not only shift the focus and/or zoom, but in order to operate effectively they may also change the focal length from the infinity quoted ones as they focus closer too. This was apparently the case with some IF macro lenses which used optical components which moved and allowed the lens to focus very close, but also increased the focal length at the closest focus position. So, in order to find out what is going on, the focal length needs to be checked at closer focus settings too. Oddly enough such data is rarely (if ever) supplied by manufacturers, although it was quite obvious with non-IF macro lenses that they increased focal length at close focus (because they increased length physically = increased focal length). IF lenses may well operate differently in terms of their shift in focal length at close focus.

I've not played around wth any of the more modern, shorter zooms but I'd say that they need fully checking to see what exactly they are doing before trying to theorise too much about them. Their first principal point may well move around too. 

It is worth commenting that with lens designs, their quoted focal length range is at infinity focus. Some modern lenses may well use internal focus/zoom optical components which, when operated, not only shift the focus and/or zoom, but in order to operate effectively they may also change the focal length from the infinity quoted ones as they focus closer too. This was apparently the case with some IF macro lenses which used optical components which moved and allowed the lens to focus very close, but also increased the focal length at the closest focus position. So, in order to find out what is going on, the focal length needs to be checked at closer focus settings too. Oddly enough such data is rarely (if ever) supplied by manufacturers, although it was quite obvious with non-IF macro lenses that they increased focal length at close focus (because they increased length physically = increased focal length). IF lenses may well operate differently in terms of their shift in focal length at close focus.
I've not played around wth any of the more modern, shorter zooms but I'd say that they need fully checking to see what exactly they are doing before trying to theorise too much about them. Their first principal point may well move around too. 

20 hours ago, Interceptor121 said:

Which means at close range the lens is no longer 28mm but could be wider
The entrance pupil instead doesn’t move with focus but may move with zooming but all tests are at 28mm

As lenses focus closer, conventional designs move the optic away from the image, so the focal length obviously increases. I doubt very much that an IF lens would widen, if for no other reason, simply because it is the widest focal length which is usually quoted by manufacturers for marketing purposes.

The entrance pupil does move albeit not a lot, because the optics move. Again, this may be different in IF lenses but my best guess is that it still moves. And it probably moves with zooms as they are zoomed too. So all ways around there are (undocumented) changes in a lens's characteristics which will need to be ascertained by testing as manufacturers rarely publish such data.

From what i see as focus distance decreases focal length drops
It is the case of macro lenses
Some 100mm lens drop to 70mm at close range
This is why the lenses may vignette more at close range as the field of view increased
The focal
Optical bench hub has many examples like this you can see the changes as the focus position changes
Bill Claff has many models for hundreds of lenses where a patent file could be found


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1 hour ago, Interceptor121 said:

From what i see as focus distance decreases focal length drops.

Think about it. As you focus closer the lens extends which by definition is increasing the focal length, because the focal length is the distance from the lens to the image it produces (in simplistic terms anyway).

6 hours ago, Paul Kay said:

Think about it. As you focus closer the lens extends which by definition is increasing the focal length, because the focal length is the distance from the lens to the image it produces (in simplistic terms anyway).

The opposite as you focus closer entrance and exit pupil get closer making the focal length shorter

Although the exact effect varies from lens to lens and in some cases the angle of view goes up in others goes down there is a trend for a lens behind a wet lens to vignette more at close range this based on practical experience and confirmed by the nauticam port charts that have notation in few cases of vignette at close range

On 4/15/2023 at 6:39 PM, Interceptor121 said:

Not sure I can align on this

The lens entrance pupil is what gets the light inside the lens the lens exit pupil is what sends the lens to the sensor

The diameter of the overall lens is mostly influenced by the focal length and the physical maximum aperture which is normally achieved when the lens is zoomed

The diameter of the glass in front is driven by those considerations

If a lens is fast like a 28-70 f2.8 the distance from the wet lens is a compromise with mechanical vignetting that happens as you move the wet lens away

For the small kit lenses like the sony 28-60 or nikon 28-70 those lenses are so small and have such a tiny aperture that will vignette very far away from the lens even if the infinity field of view is still the same

For those lenses that don’t really extend when zooming you have a choice if you put them close to the rear of the wet lens or further away

Nauticam has told me that they go through the various extensions they have and compare results if those are good they don’t go and create a new extension ring

We have had a case with the nikon 28-70mm and the wacp-c where the extension of 30mm would vignette so they had to make ad hoc a shorter one for that lens

In simple term a slower lens will always be smaller of a larger lens at equal zoom range example sony 28-70 55mm filter size vs sigma 28-70 67mm filter size

This means the sony 28-70 will vignette less and due to the construction (the lens is longer at 28mm) will preserve the entire zoom range

This lens uses the extension ring 50 and adding the 25mm inside the WACP-C has a gap of 5mm from the front of the lens

Performance is adequate full zoom range is supported -> no need for custom 45 extension

Now look at sony 28-60mm this lens has an even smaller physical aperture and again the lens is built in such a way that at 28mm is 1mm less in length than it is at 60mm

Nauticam goes for the shortest 30 extension the lens has a gap of 1cm performance is good no vignetting-> no custom extension to be made

Same lens with wacp-1 N120 has a gap of 1.5 cm so it doesn’t get the * of best performance that goes to the shorter N100 mount with 30 extension

In summary i think this is more a case or working with what they have and selecting the extensions they have and checking performance instead of starting green field for each lens

So for me this doesn’t conclude at all that a gap is required to improve performance it is just a consequence of the constraints set and the way the lens is built

 

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I'm referring to the exit pupil of the WWL/WACP.  You need the right geometry and spacings so that the lens on the camera can see the entire exit pupil.

7 hours ago, ChrisRoss said:

I'm referring to the exit pupil of the WWL/WACP.  You need the right geometry and spacings so that the lens on the camera can see the entire exit pupil.

My understanding is that those optics are afocal so they should not change the rays in and out within reason

I see on the WACP-C chart that 4 lenses have the comment

slight vignetting when focus distance from port to subject is less than 10cm at 28mm

Those lenses are Canon EF 28-70, Canon EF 28-80, Nikon AF 28-70 and Panasonic 24-105

If you move the lens in and out you see a marginal increase of field of view as you get the lens closer, when the lens is too far away it starts blurring the edges substantially

13 hours ago, Interceptor121 said:

My understanding is that those optics are afocal so they should not change the rays in and out within reason

I see on the WACP-C chart that 4 lenses have the comment

slight vignetting when focus distance from port to subject is less than 10cm at 28mm

Those lenses are Canon EF 28-70, Canon EF 28-80, Nikon AF 28-70 and Panasonic 24-105

If you move the lens in and out you see a marginal increase of field of view as you get the lens closer, when the lens is too far away it starts blurring the edges substantially

That may be but what you describe even if it is not technically an exit pupil seems to indicate it has a circular region on the rear element where the image quality is good and for the lens to cover that region fully the spacing needs to be correct.  The behavior of those lenses you mention sounds like they increase their field of view as they focus closer and manage to reach the edge of the rear element when focused close. 

For me the example is what happened with the Nikon 28-70mm
The lens used a 30mm extension and vignetted at 28mm the lens is 87mm long so it only has 3mm space
It could not use the 25mm as that is too short and it would not fit the lens
You do your tests at 80 cm and cut back the extension to 29.3mm it now has 2.7mm space
However later you found out it vignettes at close range

It seems to me exactly as I said they use the closest available extension that ensures the 28mm
If there is a gap and performance is ok they don’t design a new part unless it vignettes
Field of view is more important than spacing the lens a set amount
Another example is the sony 28-70mm it is 95 long it won’t fit the 40mm extension ring with the 50mm it doesn’t vignette good enough move on
It is safe to assume that the lens can go from 0 to 1+ cm without significant performance difference for very small slow lenses that won’t vignette
Larger aperture lenses will vignette more easily and end up with a limited zoom range
At the end past 40mm these optics are not that wide at all a 24mm lens has overall more field of view vertically and same horizontally that you got some squashed edges with a water contact optic doesn’t really matter


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I have not had the time to keep up with this thread but I would agree that the length of the extension recommended can make a significant difference as 121 has pointed out. Regarding the Nauticam WACP-C, I tested it with the recommended N100 30 extension on the Nauticam NA-A1 housing, the same one I believe 121 used for his tests which has the highest Nauticam recommendation.

Today I tested the WACP-C on the Marelux MX-A7RV housing and with the Marelux recommended extension and  the results regarding getting the lens closer to the back of WACP-C are correct. The Marelux version renders a wider field of view at 28mm. Both the 28mm end and the 60mm end will focus on the glass. From four inches to the subject the images are outstanding.

Also remember that the pool steps are rounded so that is not barrel distortion, in fact the lines are quite good.

Both photos are FULL FRAME no crop, both are at the 28mm end, the Nauticam, first image is at F/5.6 and the second Marelux image is at F/11 which does not change overall FOV.

@Phil, so what is the actual extension you're using there? That difference in FOV is pretty wild. 

I have not had the time to keep up with this thread but I would agree that the length of the extension recommended can make a significant difference as 121 has pointed out. Regarding the Nauticam WACP-C, I tested it with the recommended N100 30 extension on the Nauticam NA-A1 housing, the same one I believe 121 used for his tests which has the highest Nauticam recommendation.
Today I tested the WACP-C on the Marelux MX-A7RV housing and with the Marelux recommended extension and  the results regarding getting the lens closer to the back of WACP-C are correct. The Marelux version renders a wider field of view at 28mm. Both the 28mm end and the 60mm end will focus on the glass. From four inches to the subject the images are outstanding.
Also remember that the pool steps are rounded so that is not barrel distortion, in fact the lines are quite good.
Both photos are FULL FRAME no crop, both are at the 28mm end, the Nauticam, first image is at F/5.6 and the second Marelux image is at F/11 which does not change overall FOV.
 
 
 

13 hours ago, Matt Sullivan said:

@Phil, so what is the actual extension you're using there? That difference in FOV is pretty wild. 

For you and 121 Marelux uses what they call a five inch (127mm) port opening for all Marelux housings. As pointed out in other posts the camera sits farther back in the housing and a 20mm Marelux extension is roughly equal to a Nauticam housing with the N100 to N120 35.5mm port adapter. The Marelux port adapter for the WACP-C is a custom five inch to N100 17mm adapter. I have similar tests with WACP-1 using Nauticam N100 to N120 35.5 adapter and Marelux to Nauticam 20mm adapter and the results are a bit closer. If I have an opportunity to locate a WACP-1 with the N100 mount I will give it a try on this new 17mm extension.

@Phil Rudin did you notice any difference in lens flare between the two set ups, main challenge I’ve had with the WACPC and Sony A1 using Nauticams recommended extensions.

[mention=2618]Phil Rudin[/mention] did you notice any difference in lens flare between the two set ups, main challenge I’ve had with the WACPC and Sony A1 using Nauticams recommended extensions.