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12-24 corners


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#1 Kasey

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Posted 31 August 2003 - 03:39 PM

I've been fairly happy with the results from my 12-24. I've been shooting behind the aquatica dome with the port extension for the 105mm micro. I've been waiting patiently for Aquatica to make official recommendations on housing that lens, but still nothing after 2 months. Anyway, I took this today, and got a really screwy result in the bottom right corner of the frame. I think that the coral may have fallen inside the minimum focus distance and caused this effect but I'm not sure. James - I know you are using a different extension - is it longer or shorter than mine? would a diopter help - I own a canon 500D 2element diopter that will fit this lens. Or perhaps I just need to not get so close - but then that is why I bought such a wide lens.

Bob - I'd especially appreciate your input here on the cause of this artifact.

Scorpio - what extension do you use?

Thanks guys
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#2 Cybergoldfish

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Posted 31 August 2003 - 03:44 PM

Which dome are you using?

#3 Kasey

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Posted 31 August 2003 - 04:15 PM

It is the 8" dome - houses fisheye and all other wide angle lenses.
Seacam F100;D2x; 60mm;105mm;16mm;17-35; 10.5mm;12-24mm
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#4 james

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Posted 31 August 2003 - 04:27 PM

Yes, I too got unacceptable results from the extension ring for the 105. It just "looked right" so it was the first ring I tried w/ the 12-24, but it is too long.

I am happiest (that's my scientific opinion) with the 15mm long ring. I have posted this information here on Wetpixel a few times as the ring I recommend. I haven't shot the lens w/ a diopter, as I found I didn't need one, but I'm sure it can't hurt. Perhaps a +2

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James
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#5 james

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Posted 31 August 2003 - 04:28 PM

PS. If you focused on the diver, then you're probably just running out of nearfield DOF on the right. With the small photo you posted, it's hard to tell. Can you post some larger examples?

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James
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#6 Cybergoldfish

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Posted 31 August 2003 - 04:33 PM

I agree, I think it's just a DOF problem. The 8" dome shouldn't cause any aboration with the ext ring you are presently using, if it were it would be visible on all the corners.

#7 Kasey

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Posted 31 August 2003 - 04:47 PM

here it is
Seacam F100;D2x; 60mm;105mm;16mm;17-35; 10.5mm;12-24mm
Sea & Sea strobes
www.underthecaribbean.com