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Using the "wrong" extension ring for your lense

extension ring lense wrong

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#1 dpoursanidis

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Posted 15 April 2015 - 04:42 AM

Hi !

 

A question arrise when i have (or we) to choose/use a new lense that needs a new extension ring (sometimes less that 5-6mm)  shorter or longer from what we have (or we can affort to buy....).

 

What is your opinion/experience on this ?

 

 



#2 TimG

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Posted 15 April 2015 - 04:56 AM

Hi dpoursanidis

 

It depends! If you are shooting wide-angle, the extension ring  (EXR) length is key as it sites the lens in the correct position for the curve of the domeport. So you do need the right length for shooting wide-angle.

 

It's maybe not so crucial if shooting with a flatport and macro. It would the depend on whether the port/EXR combination creates any sort of vignetting which spoils the image you want to create. Chances are a few millimetres here and there will not make too much of a difference. But.... it might!

 

Sorry, maybe this is not terribly helpful but it certainly is my experience. In short: wide-angle/domeports: yes EXR is important. Macro/flatport, maybe not.


Tim
(PADI IDC Staff Instructor and former Dive Manager, KBR Lembeh Straits)
Nikon D500, Nikkors 105mm and 8-15mm, Tokina 10-17mm,  Subal housing

http://www.timsimages.uk
Latest images: http://www.shutterst...lery_id=1940957


#3 dpoursanidis

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Posted 15 April 2015 - 12:10 PM

Hi Tim

 

Example first > Aquatica mini dome + Canon 8-15 + 18453 EXR =

 

 

Center crop

 

https://copy.com/DxwZqGGdLV8i92L1

 

 

Low right crop

 

https://copy.com/yIZvbHuxUjCd0WIE

 

 

How much "better" can these be with the correct ?

 

Images are from RAW > JPEG. No editing.

Natural light shot @ 2m depth.



#4 TimG

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Posted 15 April 2015 - 10:23 PM

Hi dpousaindis

 

Hmmm, not sure what to say!

 

"Better" is a pretty subjective word. Certainly you have some pretty serious blurring going on there and I would have thought you should be able to get it much "better" than that! Sometimes though it depends how much you are prepared to pay to make a difference; and then how much the difference is worth the cost.

 

I'd start by checking Aquatica's recommendations for the setup for their mini dome and Canon 8-15. If you have the wrong EXR then, bingo, you have the start of the problem and the cost of a fix is "relatively" (ha!) low. And does that combination need, for example, a diopter? If both those questions are resolved and you still have blurring, then the issue could be one that the 8-15 doesn't work well with a mini dome and you might need a larger dome and then the cost of a fix increases rapidly - and hence my rather philosophical question as to whether the solution to the problem warrants the cost of the fix.

 

But, as I said in the first reply, the right EXR is important when using a dome. Start there would be my suggestion.....


Tim
(PADI IDC Staff Instructor and former Dive Manager, KBR Lembeh Straits)
Nikon D500, Nikkors 105mm and 8-15mm, Tokina 10-17mm,  Subal housing

http://www.timsimages.uk
Latest images: http://www.shutterst...lery_id=1940957


#5 dpoursanidis

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Posted 16 April 2015 - 12:23 AM

Thanks Tim

 

The fix cost 250 euros (EXR) so just paid for :)

 

Diopter for this lense is not something that i have see/read around, so the EXR will solve this.

 

Bigger dome is also an option but for CFWA staff.

 

Dimitris



#6 TimG

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Posted 16 April 2015 - 01:18 AM

Good call, Dimitris. Fingers crossed the EXR does the trick.

 

Fingers crossed too you don't need the bigger dome! They aren't much help for sure with CFWA as they make it far more difficult to get the strobes in the right position: almost impossible I've found.


Edited by TimG, 16 April 2015 - 06:50 AM.

Tim
(PADI IDC Staff Instructor and former Dive Manager, KBR Lembeh Straits)
Nikon D500, Nikkors 105mm and 8-15mm, Tokina 10-17mm,  Subal housing

http://www.timsimages.uk
Latest images: http://www.shutterst...lery_id=1940957






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