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Thread started 31 May 2018 (Thursday) 08:16

# Hyperfocal distance underwater and at water level.

May 31, 2018 08:16 |  #1

Hey all.

I was wondering if anyone could get deep and detailed on explaining how to achieve hyperlocal distance while shooting with both dome and flat ports in and at the waters surface? With a dome port it is clear that the shape of the dome has a drastic effect on focus distance, I grasp a touch of the physics involved in this but cant really put it into practical use.

I am looking to close down my aperture and shoot largely in manual focus but notice through trial and error I am having varied success and it is not working the same as a camera out of a housing.

I think some irrelevant details might be: 5d mk IV or 1dx mk II in aquatech housings with a mix of dome and flat ports, lenses range from 16-35 2.8 mkiii, 24-70 2.8 mk II or 135 f2 predominantly.

I am close to calling up aquatech and begging them for a lesson. Hope this helps having a discussion here.

Thank you!

Erik

Erik
ErikOlsenPhoto.com

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Jun 06, 2018 18:29 |  #2

You can find the formulas for doing calculations here:
https://www.scubageek.​com/articles/wwwdome.h​tml

Basically it is far too complicated to explain in one post!

The bottom line is that if you want to focus both above and below water doing what is called an over/under shot, use a fisheye lens with a very large dome port such as a superdome (9" diameter). The only way to get reasonable focus above and underwater at the same time if that is what you are trying to do.
Tom

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Jul 01, 2018 10:17 as a reply to  @ fish_shooter's post |  #3

Thank you for the reply fish_shooter.

I am trying to determine how a port will act both in and out of the water. I will be shooting some split water but am looking for the behavior in respect to hyperlocal distance of a dome port essentially in air alone. I assume it would be a non issue with a flat port. I do wish to understand hyperlocal distance underwater, of which I think that link will be very helpful!

Thanks
Erik

Erik
ErikOlsenPhoto.com

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Jul 03, 2018 01:38 |  #4

EOlsenPhoto wrote in post #18654473
Thank you for the reply fish_shooter.

I am trying to determine how a port will act both in and out of the water. I will be shooting some split water but am looking for the behavior in respect to hyperlocal distance of a dome port essentially in air alone. I assume it would be a non issue with a flat port. I do wish to understand hyperlocal distance underwater, of which I think that link will be very helpful!

Thanks
Erik

The above water part is essentially like shooting through a window: the shift in focus is tiny. A fraction of the glass thickness. Therein lies the problem: the above water is at normal distances, i.e., far away whereas the u/w part is a virtual image that is very close (depends on dome diameter, see formulas in link I left before). Thus large domes and fisheye lenses are used: you need a lot of DOF which fisheyes provide.

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Jul 10, 2018 12:09 as a reply to  @ fish_shooter's post |  #5

Great. Thank you Fish_shooter!

Erik
ErikOlsenPhoto.com

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Hyperfocal distance underwater and at water level.
AAA
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