АлександрД
Contributor
I have to wright this big introduction for more clean understanding of reason 
rework process will be in the next messages.
Some short jump to the side, about UNnormal mask and it`s technology.
When I just start to be a diver, I already was "advanced snorkler" (not like freediver, who can dive to 30+m, but 15m was not a problem), and at that moment I used Aquasphere mask. And for me any other "normal" mask (with flat glass) was like horse blinders.
It has widest angle of sight, from any other normal masks (I will not compare it with Hydrooptics, because it is not normal mask
)
Aquasphere mask
As you can see - it has not flat, but spherical glases, with changable radius.
Even in front of your eyes it also spherical, but with big radius.
Yes, here could be a question - how you eyes looks front, and see single picture, not double, like with fireman`s gasmask with single spherical glass?
or like that mask for example:

Reason is very simple. In any looking angle, does not matter, when you eyes looks left or right, you line of sight for any angle - is orthogonal to the glass surface (or as close as possible to that)!
But on the sides, where only one eye can have a look outside (other eye closed by nose) it also not disturbing, and you also have single picture.
Is anybody know about Berg mask?
It was first, used such principle.
You can see - it has same, spherical glases, just in front of you eyes.
But those sperical surface required not olny for wide view, but most important - for same environment sizes as above wataer, as below!
When you diving under water near the column, for example, or even put just one half of the face underwater - you can imagine - size (diameter) of column it the same as under, as below water surface!
This brings you also one, very important advantage - brightness of all things underwater (in compare with normal mask) is near twice bigger! It is not a joke!
You can easy compare, and here enough just two knowleges - one constant from PADI book (physical constant) and ability to count from 1 to 16
PADI OWD manual, chapter 2, page 75 (Russian edition, 2008)
All viewable sizes of any object underwater looks 33% bigger, than in the air.
But ok, will take English (I have just from 2000) - page 71 - "...objects under water appear 25% larger..."
It means followng: when you take object like square, you will have such picture:
LightBlue - IMAGE of the object on the surface.
Darkblue - how it looks under water.
So, just imagine - we have same object, same light conditions, and absolutelly clear water.
Light, that came from object, on the surface conditions - fills 9 squares.
Same ammount of light, from the same object, but underwater fills 16 squares!
We can compare squares (ammount of squares) with our light sensors in our eyes.
So we have same (as for 9) volume of the light, but falling to the 16 sensors!.
It mean that total brightness will 16/9 ~= 1.7 times less than original brightness.
It is the same meaning, that brightness of objects underwater in "normal" mask LOOKS near two times less!
Aquasphere keep same sight angle, as on the surface, it mean Aquasphere keep same brightness level of objects underwater! Which is near two times bigger, than other masks!
so... now about FullFaced mask....
For our climate and cold water, or for nice, but dangerous places (like acid lakes) is best way - to use Full Face Mask. But as I know - there is noone manufacture of the masks with like a Berg mask glases. All FFM (Full Face Mask) has flat glass.
BUT! Once I imagine that mask:

Shure, I bring to notice that ince girl first, but late it was very interesting, what is that mask....
My friend told me, that it is Mark IV gas mask
It was interesting for me by prescence of two inlets.
Late I found Russian gas mask PMK-2
It was possible to purchase it from "ours craigslist" for 33$ approx. for new.
So, I received following mask:
It has two inlet connection holes, but just one plastic connector for filter. Other is stub.
It used for right/left connection of filter.
to be continued...
P.S. my avatar picture - in last revision of selfmade mask

rework process will be in the next messages.
Some short jump to the side, about UNnormal mask and it`s technology.
When I just start to be a diver, I already was "advanced snorkler" (not like freediver, who can dive to 30+m, but 15m was not a problem), and at that moment I used Aquasphere mask. And for me any other "normal" mask (with flat glass) was like horse blinders.
It has widest angle of sight, from any other normal masks (I will not compare it with Hydrooptics, because it is not normal mask

Aquasphere mask
As you can see - it has not flat, but spherical glases, with changable radius.
Even in front of your eyes it also spherical, but with big radius.
Yes, here could be a question - how you eyes looks front, and see single picture, not double, like with fireman`s gasmask with single spherical glass?
or like that mask for example:

Reason is very simple. In any looking angle, does not matter, when you eyes looks left or right, you line of sight for any angle - is orthogonal to the glass surface (or as close as possible to that)!
But on the sides, where only one eye can have a look outside (other eye closed by nose) it also not disturbing, and you also have single picture.
Is anybody know about Berg mask?

You can see - it has same, spherical glases, just in front of you eyes.
But those sperical surface required not olny for wide view, but most important - for same environment sizes as above wataer, as below!
When you diving under water near the column, for example, or even put just one half of the face underwater - you can imagine - size (diameter) of column it the same as under, as below water surface!
This brings you also one, very important advantage - brightness of all things underwater (in compare with normal mask) is near twice bigger! It is not a joke!
You can easy compare, and here enough just two knowleges - one constant from PADI book (physical constant) and ability to count from 1 to 16

PADI OWD manual, chapter 2, page 75 (Russian edition, 2008)
All viewable sizes of any object underwater looks 33% bigger, than in the air.
But ok, will take English (I have just from 2000) - page 71 - "...objects under water appear 25% larger..."
It means followng: when you take object like square, you will have such picture:
LightBlue - IMAGE of the object on the surface.
Darkblue - how it looks under water.
So, just imagine - we have same object, same light conditions, and absolutelly clear water.
Light, that came from object, on the surface conditions - fills 9 squares.
Same ammount of light, from the same object, but underwater fills 16 squares!
We can compare squares (ammount of squares) with our light sensors in our eyes.
So we have same (as for 9) volume of the light, but falling to the 16 sensors!.
It mean that total brightness will 16/9 ~= 1.7 times less than original brightness.
It is the same meaning, that brightness of objects underwater in "normal" mask LOOKS near two times less!

Aquasphere keep same sight angle, as on the surface, it mean Aquasphere keep same brightness level of objects underwater! Which is near two times bigger, than other masks!

so... now about FullFaced mask....
For our climate and cold water, or for nice, but dangerous places (like acid lakes) is best way - to use Full Face Mask. But as I know - there is noone manufacture of the masks with like a Berg mask glases. All FFM (Full Face Mask) has flat glass.
BUT! Once I imagine that mask:

Shure, I bring to notice that ince girl first, but late it was very interesting, what is that mask....
My friend told me, that it is Mark IV gas mask
It was interesting for me by prescence of two inlets.
Late I found Russian gas mask PMK-2
It was possible to purchase it from "ours craigslist" for 33$ approx. for new.
So, I received following mask:
It has two inlet connection holes, but just one plastic connector for filter. Other is stub.
It used for right/left connection of filter.
to be continued...
P.S. my avatar picture - in last revision of selfmade mask
