Depth of field calculators.

[Nickbell]

I am still getting used to using the 9-18 mm & 8mm fisheye lenses underwater on my em1. I frequently consult a DOF calculator / app for topside use and was wondering what adjustments / recalculations (if any) need to be made for use when shooting underwater. I understand the magnification when using a flat port would affect calculations, but as a dome port retains original angle of view, would the topside calculations be correct, or are there complications due to the camera re-focussing on the new image point inside the dome. Could someone give me any calculations for both a flat port or dome port, or ways of re-interpreting the figures from the DOF calculators. Thanks.

 

[gert7to3]

It seems you may be overthinking this, but that's me, not you. Basically I would do some test shots of subjects lined up on a rule.
You might try PMing Phil Rudin or Jack Connick here on ScubaBoard.

Some on line sites may help.

Aperture, F-stops and Depth of Field|Underwater Photography Guide

Shallow Depth of Field Underwater|Underwater Photography Guide

 

[bvanant]

I think you need to remember that the virtual image is curved and this means some loss of DOF compared to a planar subject, hence fuzzy corners. That being said, I think the rules are the same in general and DOF calculators can be used but for most fisheye lenses no calculations needed.
Bill

 

[Interceptor121]

You can't use a depth of field calculator for a fisheye lens but you can with a rectilinear wide angle lens behind a dome port as is. For a flat port I also use the same settings as it is true that you get in water magnification however your focus point moves backward so after all it's the same as well. For what concerns fisheye lenses the Panasonic 8mm is sharp in the corners pretty much as each aperture the same as it is on land based on my practical experience. For rectilinear lenses instead due to the dome port you usually need an additional stop. Eventually when you hit an aperture that has hyper focal distance same as the minimum focus distance of the lens there is no point increasing that any more. For my 7-14mm Panasonic this is f/13 anything smaller doesn't increase sharpness. I do however shoot the lens at f/8 and sometimes wider as centre performance drops after f/8 as diffraction kicks in. There is no point having sharper corners if the centre is not at best