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Over under issues


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#1 Scott Ferris

Scott Ferris

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Posted 24 September 2013 - 03:56 PM

Hi all,

 

Gear is:

Canon 5D mk3
Sigma 15mm/2.8 Fisheye
IKELITE housing
IKELITE dome 8" + wide angle adaptor/tube

 

Struggling to get over part of image focused, underwater part is well focused, is this a tube length focus issue or my stupidity?

 

Many thanks for any help.


Edited by Scott Ferris, 24 September 2013 - 03:57 PM.


#2 Tom_Kline

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Posted 24 September 2013 - 04:44 PM

You need to stop the lens down to maximize the depth of field. If your underwater subject is very close you will not be able to get near-infinity sharply in focus too.


Thomas C. Kline, Jr., Ph. D.
Oceanography & Limnology
Canon EOS-1Ds MkII and MkIII and Nikon D1X, D2X, D2H cameras. Lens focal lengths ranging from 8 to 180mm for UW use. Seacam housings and remote control gear. Seacam 150D and 250D, Sea&Sea YS250, and Inon Z220 strobes.
www.flickr.com/photos/tomkline/

 

 


#3 Scott Ferris

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Posted 24 September 2013 - 05:17 PM

Thanks Tom, I am pretty sure that is my stuoidity, I just checked the EXIF and the test shots at an indoor pool (!) were f4.5, nowhere near enough to encompass both focus points.

 

Thanks again, Scott.



#4 markw

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Posted 04 October 2013 - 04:44 AM

I'm interested in trying some over under shots and have seen suggestions that an graded ND filter helps with over under pics. What value ND is recommended?

Thanks,
Mark