39 replies to this topic

[Lwang]

He he he, me still confuse on lens 101.

Just to repeat.
With water or air ( I managed to seal the gap ), the Inon H100 on RX100 is the same FOV underwater.
Me tested already.
.

Yeah...that's what I said... cuz you have your flat port's image is not coming from the subject itself...it is coming from another lens that has already reduced the size of its image bcuz it went from air to water....so u end up with no image size change....your flat port magnifies that unmagnified image, and result image size is 1x.

[Interceptor121]

So the lens field of view in air is 179 degrees with a dome added and in water it comes to 144.8.

If the dome was meant to keep that fov where are have the 34.2 degrees been lost?

Coverage underwater with dome lens is less than coverage in air because water filling the space between the housing port and the UWL-100 rear element increases the effective focal length of the camera lens

Edited by Interceptor121, 29 October 2012 - 09:37 AM.

[SPP]

INON spec as pointed out by 121 : http://www.inon.jp/p...028m67/top.html

●Dual use (land/underwater) wide conversion lens specially designed for 28mm wide camera (35mm film equivalent). The maximum view angle is 100.8° underwater for wide imaging and 179° on land for fish-eye imaging.

●Optional "Dome Lens Unit II for UWL-H100" further increases maximum view angle to 144.8° underwater for semi-fisheye imaging.

We know all viewing underwater get magnified. Same for our camera lens right ?
Assume 33% magnification.

Is it possible that the DOME recovered back the lost magnification due to water, but since it is in water and must also experience magnification by water and hence only 144.8 degrees achieved or exta 40 degrees ? If say Inon is accurate ( I am sure they are ) 78.2 degrees lost from H100 while in water compared air, is then re-gained by DOME but also lost to water magnification. So overall the DOME actually is not bad, yes ?

I don't know if this will help

http://www.camerasun...on-uwlh100-28ld

http://scubageek.com...es/wwwbigr.html

Sorry me lens dummy.
.

Edited by SPP, 29 October 2012 - 09:43 PM.

[Interceptor121]

The lost field of view compared to air depends on the water between the port and the back of the wet lens. Say that in air that distance is 2mm once you put it with water that becomes 2*1.339=2.678
As the camera has a focal multiplier of 2.7 is like you zoomed in additional 1.83 mm at 35mm equivalent so you are now at 30mm before hitting the lens and not anymore 28mm as you were in air. This explains why you still loose some field of view
End of the lesson!

[oskar]

Slightly different topic, but I wonder whether it is feasible to convert my S&S DX-1G wet lens to a Nauticam RX100 housing. It works well with that 24mm lens and has the inner lens diameter 42mm, which seems big enough. The S&S plastic bayonet unscrews and a well centered 67 to 50 something step up ring will fit using the original screws with some careful drilling.

Is that likely to work?

//O

[Interceptor121]

The quality of the image will depend on how close the back of the lens is to the port. If you get hold of a Nauticam housing it is worth trying

[Lwang]

The lost field of view compared to air depends on the water between the port and the back of the wet lens. Say that in air that distance is 2mm once you put it with water that becomes 2*1.339=2.678
As the camera has a focal multiplier of 2.7 is like you zoomed in additional 1.83 mm at 35mm equivalent so you are now at 30mm before hitting the lens and not anymore 28mm as you were in air. This explains why you still loose some field of view
End of the lesson!

not sure how you get focal multipler of 2.7 or 2.678. But if an object looks bigger, it should look like it is closer, not farther away.

There is a point where when you have a wider lens, all you are going to see is vignetting from the edge of the wet lens. I am not sure how your housing/lens relationship interact with the wet lens, but with mine, even if I pull the wet lens forward 5mm, there is no vignetting in its widest setting, so there is a little bit of extra built into the wet lens.

Anyway, flat port multipler is not linear. If you put an object 0.1mm in front of a flat port, it will not magically look 1.33x bigger. If it does, any object that is stuck to the front of your mask, then suddenly pulled away ever so slightly, will have a drastic jump in image size, which it don't.

For a port to wet lens and port to camera lens of 2mm, and a nodal point of 26mm (which seems to be my camera's nodal point), the magnification effect by the water is only 1.016, which is 1.6%. That is too small to account for any variation in field of view (this doesnt take into account of the subject getting demagnified when the light goes from air to water medium of the rear of the wet lens(like looking at one's eyes thru scuba mask).

Slightly different topic, but I wonder whether it is feasible to convert my S&S DX-1G wet lens to a Nauticam RX100 housing. It works well with that 24mm lens and has the inner lens diameter 42mm, which seems big enough. The S&S plastic bayonet unscrews and a well centered 67 to 50 something step up ring will fit using the original screws with some careful drilling.

Is that likely to work?

//O

I guess you have to see what the S&S wet lens' rear element's OD and the image size it throws out (should be pretty much the diameter of the rear element at close range. Should be larger than your camera's lens, and it should be able to mount very close to the rear port. The exit pupil has to be a bit larger than the camera's front element. Putting a cameraphone's lens 1 inch behind the wet lens will produce much better result than putting a large format camera's lens at the same distance.

[Interceptor121]

I calculate the focal length multiplier through the ratio between chip diagonal and 35mm diagonal it is a standard formula in camera optics.

The 2mm space does not change but due to water magnification is like zooming in and therefore loosing field of view as if the lens was more extended than it really is.

This is pretty crystal to me am not sure why it isn't to you but maybe you can have a word with Inon yourself to be more happy also cameras underwater website is quite helpful

not sure how you get focal multipler of 2.7 or 2.678. But if an object looks bigger, it should look like it is closer, not farther away.

There is a point where when you have a wider lens, all you are going to see is vignetting from the edge of the wet lens. I am not sure how your housing/lens relationship interact with the wet lens, but with mine, even if I pull the wet lens forward 5mm, there is no vignetting in its widest setting, so there is a little bit of extra built into the wet lens.

Anyway, flat port multipler is not linear. If you put an object 0.1mm in front of a flat port, it will not magically look 1.33x bigger. If it does, any object that is stuck to the front of your mask, then suddenly pulled away ever so slightly, will have a drastic jump in image size, which it don't.

For a port to wet lens and port to camera lens of 2mm, and a nodal point of 26mm (which seems to be my camera's nodal point), the magnification effect by the water is only 1.016, which is 1.6%. That is too small to account for any variation in field of view (this doesnt take into account of the subject getting demagnified when the light goes from air to water medium of the rear of the wet lens(like looking at one's eyes thru scuba mask).

Edited by Interceptor121, 30 October 2012 - 01:09 PM.

[Lwang]

I think you got the numbers backward. Subject would appear 25% closer:

http://scubageek.com/articles/wwwclosr.html.

But you have to take into account of the camera lens to port distance and camera lens to nodal point (the location inside the lens where the image forms, before it gets manipulated and/or extended to re-form the image at the sensor location).

Thus, if you take all that into account, with 2mm spacing from wet lens to port and 2mm spacing from port to camera lens, and 26mm nodal point, the magnification will be only 1.6%. Formula here:

http://scubageek.com/articles/wwwbigr.html


Here is an old writeup on this forum on the wide angle wet lens:

http://wetpixel.com/forums/index.php?showtopic=23678

It talk about all the stuff I mentioned, such as the need for constant camera lens to wet lens distance (as indicated by my indication of internal zooming), nodal point sensitivity (issues when zooming to telephoto range), large rear element requirement (large exit pupil).

And a very simple description of the lens, with above and under water ray tracing:

http://www.seafriends.org.nz/phgraph/film.htm#rebikoff

[Interceptor121]

Or 33% larger which is the additional zoom or 25% closer so you need to multiply times 1.33(9)
No confusion

I think you got the numbers backward. Subject would appear 25% closer:

http://scubageek.com/articles/wwwclosr.html.

But you have to take into account of the camera lens to port distance and camera lens to nodal point (the location inside the lens where the image forms, before it gets manipulated and/or extended to re-form the image at the sensor location).

Thus, if you take all that into account, with 2mm spacing from wet lens to port and 2mm spacing from port to camera lens, and 26mm nodal point, the magnification will be only 1.6%. Formula here:

http://scubageek.com/articles/wwwbigr.html


Here is an old writeup on this forum on the wide angle wet lens:

http://wetpixel.com/forums/index.php?showtopic=23678

It talk about all the stuff I mentioned, such as the need for constant camera lens to wet lens distance (as indicated by my indication of internal zooming), nodal point sensitivity (issues when zooming to telephoto range), large rear element requirement (large exit pupil).

And a very simple description of the lens, with above and under water ray tracing:

http://www.seafriends.org.nz/phgraph/film.htm#rebikoff

[kkfok]

If I want to use M67 version of this lens, should I buy type 1 or type 2? Thanks.

[Interceptor121]

Which housing?

[kkfok]

Which housing?

nauticam, thanks.

[Interceptor121]

Type 2

[kkfok]

Type 2

Thanks.

[SPP]

Get Type 2 if using Nauticam housing. My box said it is type 2.

below is type 1 with type 2 description
http://reefphoto.com...roducts_id=5313

It said Type 1 is for different housing.

Have fun shopping my man.......

[oskar]

On modifying the S&S baynet lens. As I said the rear lens element is 42mm in diameter, what is the diameter of lenses that currenlt are know to work, such as the UWL-H100?

Cheers
/O

Slightly different topic, but I wonder whether it is feasible to convert my S&S DX-1G wet lens to a Nauticam RX100 housing. It works well with that 24mm lens and has the inner lens diameter 42mm, which seems big enough. The S&S plastic bayonet unscrews and a well centered 67 to 50 something step up ring will fit using the original screws with some careful drilling.

Is that likely to work?

//O

I guess you have to see what the S&S wet lens' rear element's OD and the image size it throws out (should be pretty much the diameter of the rear element at close range. Should be larger than your camera's lens, and it should be able to mount very close to the rear port. The exit pupil has to be a bit larger than the camera's front element. Putting a cameraphone's lens 1 inch behind the wet lens will produce much better result than putting a large format camera's lens at the same distance.

[Interceptor121]

On modifying the S&S baynet lens. As I said the rear lens element is 42mm in diameter, what is the diameter of lenses that currenlt are know to work, such as the UWL-H100?

Cheers
/O

42 mm is plenty however you will need to see how close will the lens be to the port
What's the diameter of the thread on the lens?

[Jensm]

Any idea if RX100 will work with the UWL-100 Achromat type 2? (ie. not the UWL-H100)

Thanks a lot

Jens

[Interceptor121]

Any idea if RX100 will work with the UWL-100 Achromat type 2? (ie. not the UWL-H100)

Thanks a lot

Jens

I haven't had the opportunity to try the lens itself however I wrote something on my blog interceptor121.wordpress.com with regards to video modes

I believe it will work well for video in active mode but vignette for stills until approximately 32mm zoom