How much distance for 8" Dome for Tok FE?

My DIY project is to make an adapter so I can use an old 8" dome port for my ancient Oceanic Hydro 35 F1 housing to fit on my digital Ikelite housing using my Tokina 10-17 FE zoom.

The plan is to sacrifice an old Ike macro port, cut off the lens end and gluing a customized acrilyc adapter that will fit my 8" Oceanic dome.

This is the question I have for those in the know:

1. How far should the dome be from the lens? I already played around with the dome and housing and found the maximum distance where the corners of the port are not showing. Is this all that I need to care about? Or should the dome curvature match the lens curvature more for edge to edge sharpness? I currently use the 6" Ike port, and it would seem logical that the 8" can be a little further away from the lens by the increased dome surface. But how much?

2. Maybe, some of you reading this have the Ike modular 8" dome port on an Ikelite housing for a Canon with a Tok.

a. How far is the dome from the housing?

b. How far is the lens from the inside of the dome when fully cranked out at 17?

3. Is there any formula to determine ideal lens placement to dome curvature, or is this just a trial and error process?

I'm interested in doing more over/under with the 8" dome (since I have it just sitting, since going digital).

Thank you in advance for any insight to this DIY project.

OK. So I searched and read articles on "Dome Theory" with the most useful being here on Wetpixel <http://wetpixel.com/i.php/full/dome-theory/>. The Tok 10-17 FE zoom should be able to focus on the virtual images of the 8" dome. But I'm still wondering which lens to dome distance is ideal to allow corner sharpness within the full 10 to 17 zooming range. Can anybody provide me with some insight how the Tok behaves behind an 8" dome from experience? If the 10mm zoom setting on infinity and f4 allows corner sharpness, how is the corner sharpness on 17mm? Or is there no difference from experience? Is therer a compromise? Would an adjustable dome adapter be an useful consideration? Still clueless...please help me. - Bo

OK. So I searched and read articles on "Dome Theory" with the most useful being here on Wetpixel <http://wetpixel.com/i.php/full/dome-theory/>. The Tok 10-17 FE zoom should be able to focus on the virtual images of the 8" dome. But I'm still wondering which lens to dome distance is ideal to allow corner sharpness within the full 10 to 17 zooming range. Can anybody provide me with some insight how the Tok behaves behind an 8" dome from experience? If the 10mm zoom setting on infinity and f4 allows corner sharpness, how is the corner sharpness on 17mm? Or is there no difference from experience? Is therer a compromise? Would an adjustable dome adapter be an useful consideration? Still clueless...please help me. - Bo

Hi,

I think your question is so difficult. To answer, all the information about the dome, the lens

and the special software tool such as ZEMAX may be necessary. It is the professional work.

The ideal distance between the dome and the lens are variable by the distance to the object

and the focus length of the lens.

I have made 3 dome lenses.

Two is for ZD8mm fisheye lens (E300) and one is for the semifisheye lens(G10).

The report are at

The Sea&SEa mini dome port for ZD8mmFE

The acrylic dome for ZD8mmFE

The acrylic dome for the semifisheye lens to G10 (in this forum)

When I made these domes I didn't think over the distance from lens and the dome, it was

roughly estimated. There was no serious problem in the picture (but the first dome was flooded).

When I made the acrylic dome for the semifisheye lens, I set a acryrlic dome afloat on

the bathtub and took a photo of the objects on the bottom through the dome.

I did'nt find significant difference in the variable port size (10,15,20cm diameter) and

the variable distance between the dome and lens.

So I made the semifisheye lens covered by the 9cm (cut the 10cm dome) diameter dome.

I hope you will try and report the result. Good luck.

(sorry my bad english)

------------------------------------------------

http://hanachan.ddo.jp/

Hello hanachan,

Thank you for your response to my inquiry. You are an inspiration to me and others for the DIY projects you have done and shared with us all .

I will excuse your Japanese grammar, if you excuse my Dutch grammar...LOL.

I totally understand that my question is difficult to explain and probably will have to be answered by my own trials. I promise to report on my experimentation as I go along. I hope to not experience a flooded dome, but that is a risk we all take as DIY underwater explorers Safe bathtub and pool testing will be done before the ocean.

I'm considering a possibly risky adapter design that has not been considered before to my knowledge. I will report when I get something more concrete to share.

Where did you get your domes? Does anybody know how to get the optical glass domes?

Again, thank you for your reply hanachan

Bo

I bought the acrylic dome at the internet acrylic shop. The dome is not an optical product but a general one.

The Athena sells the optical glass domes.