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lonelycat

corner sharpness or dof issue?

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I took this picture. It seems that the picture is blurred on the left quarter and top corners unnaturally.

As far as I remember, the bottom diver was lying quite in line with the rock.

 

Camera: Nikon D90 in Aquatica housing

Lens: Tokina 10-17mm w/ 8" dome port + extension ring #18456, and magic filter

Focal Length: 10mm

Apeture: F/8

Shutter speed: 1/30s

 

I'm not sure if it's a problem with corner sharpness or merely a depth of field issue. Please advise! Many thanks! Lily

 

DSC_0047c.jpg

Edited by lonelycat

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On my screen your picture looks fairly good! The divers look in focus. I note that the rock off in the distance is in focus as well. It may have been possible to improve things just a bit by having the focus point be just slightly closer. Need blow-ups of different parts of the image to make a more detailed analysis. BTW the corners are just fine as they are either sand or water. ;)

Tom

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I expected that the whole bottom diver should be as sharp / clear as its head, but .... ;)

 

It looks to me like the diver kicked up some sediment, and the water is cloudy in the area around the diver's knee. The background diver's fins are also quite close to the sand, and the background diver is much clearer from the waist up, which also makes me think of sediment in the water.

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Thanks for your reply, Tom! Here comes the photo in larger size and with remarks to indicate what I found strange ...

I expected that the whole bottom diver should be as sharp / clear as its head, but .... :wacko:

Lily

 

http://picasaweb.google.com/lh/photo/vYBob...feat=directlink

 

pls press "magnifier" button to enlarge :>

 

 

Interesting interface! Note that the bubbles in the upper left corner are sharp. No prob with your optics! :(

T

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Top right corner - looks to me as simply the variation in sunlight angle and ripples are not lit.

 

Bottom left - possibly due to reduction in light reaching the legs when distance is larger, resulting in a loss of contrast.

 

Don't see the photo as not having the right level of corner sharpness of DOF. IMHO it is light vs distance resulting in lower contrast, hence perceived sharpness.

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Top right corner - looks to me as simply the variation in sunlight angle and ripples are not lit.

 

Bottom left - possibly due to reduction in light reaching the legs when distance is larger, resulting in a loss of contrast.

 

Don't see the photo as not having the right level of corner sharpness of DOF. IMHO it is light vs distance resulting in lower contrast, hence perceived sharpness.

 

 

many thanks for all you replies, which definitely relieve my worry of have optical problems with my lens and dome..!!!

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i will second the sediment note, definitely some kicked up by the diver.

 

but there is also some motion blur in the image, resulting from a slowish shutter speed. most of the photo is sharp, but look closely at the bottom divers fins, esp. his left fin, and his bubbles just above him in front of the other diver. definitely a little motion blur from those moving elements. i think that's also why the sediment stirred up is harder to see and looks more like a soft haze. i'm guessing your shutter speed was around 1/30th (edit: ha! wrote that then looked back at ur post and indeed it was 1/30th)

 

a little odd how the surface pattern appears and disappears, but likely due to the sun angles, huge fov of the lens and probably the surface swell etc. i see nothing really wrong with your photo, the slight softness on the side and touch of motion blur are acceptable. could use a bit of a contrast boost though.

 

also, the way his legs seem to curve away from you even though you thought he was quite in line with the rock is a bit of the "tadpole effect" that one gets with a fisheye lens. if you let a divers body parts get towards teh edge of a fisheye's frame they will get distorted. cheers,

 

chris

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