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GH4: Panasonic 7-14mm f4 lens in a Zen 170mm port?


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#1 peterbkk

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Posted 17 July 2014 - 07:34 PM


I've been scratching my head over which wide-angle lens I should use for underwater use with the GH4 and the Zen 170mm. I have been reading about dome ports, virtual images, rectilinear lenses, corner sharpness, close focus distance, mathematical formulas, etc, etc. Interesting stuff but I have not found a clear answer.

I own the Panasonic 12-35mm f2.8 and it's a great lens, at least above water. It should work well in the Zen 170mm dome. Should focus OK and be sharp in the corners. I can test this lens next week when I get the GH4 housing.

But, 12mm (~24mm) is not very wide for shooting large creatures up close. Might be OK but I suspect that I'll want something a bit wider.

One option is a fish-eye like the Panasonic 8mm. But I am not too crazy about the fish-eye look for all my WA shots.

Another option is a full-frame lens (Nikon, Canon, etc) on a 4/3rds Metabones speedbooster. Could be nice for low DoF but probably loses all AF, lens corrections and stabilisation functions?

So, then I get back to what I first thought would be best lens: the Panasonic 7-14mm f4 lens. Great focal range for underwater WA (35mm ~ 14-28mm). All the Panasonic functions work: AF and lens corrections. The close focus at .25M should focus fine, although it'll right on the near focus limit of the lens.

But, here's where my reading about dome ports made me uncertain. What will the corner sharpness of the Panasonic 7-14mm be like in the Zen 170mm port?

I've read about a "rule of thumb" not to use a rectilinear WA lens greater than 100 degrees angle of view in a dome port or you get soft corners. The 7-14mm has an angle of 114 degrees at its widest. Is this going to rule out the Panasonic 7-14mm f4 lens? Could it be OK from about 10mm to 14mm in its zoom range?

Of course, one answer might be: try one. But, it's an expensive lens to buy for a pool test that might prove it unsuitable. I would have very little use for this lens if it doesn't work underwater. And, I'm sure no shop in Singapore will lend me one to test.

Has anyone tried the Panasonic 7-14mm in a dome port?

Thoughts? Solutions?

Regards
Peter


Edited by peterbkk, 18 July 2014 - 03:51 AM.


#2 kkfok

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Posted 17 July 2014 - 10:38 PM

Just a reminder, there is no OIS in 7-14.



#3 peterbkk

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Posted 18 July 2014 - 03:51 AM

Good point.  Although a super wide-angle should not need stabilisation. 



#4 Drew

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Posted 18 July 2014 - 04:04 AM

It does if you have shakey hands! :)


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#5 textilet

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Posted 18 July 2014 - 05:36 AM

I found this online when I was wondering the same thing. Corners appear OK, possibly aided by the 4k crop. Testing Panasonic GH4 Underwater:

#6 peterbkk

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Posted 18 July 2014 - 06:32 AM

possibly aided by the 4k crop.

 

Yes, although it is not ideal footage to judge corner sharpness, I can not see any obvious corner softening, even played at HD on a large monitor.

 

I think that you've answered the question with your "4K crop" comment.  Even if the dome / lens combination was softening the corners, the corners are not being recorded in any video mode.  And the side edges are chopped off in 4K mode.  

 

So, therefore, if the 12-35mm works out to be not wide enough, I assume that I can safely go ahead and buy the 7-14mm lens.

 

Regards

Peter


Edited by peterbkk, 18 July 2014 - 06:37 AM.


#7 peterbkk

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Posted 18 July 2014 - 06:36 AM

It does if you have shakey hands! :)

 

Best to avoid too much coffee before a dive.   :beer:

 

It would be nice to have image stabilisation but Mr Cheung is working on a stabilised housing modification for me.

 

Regards

Peter



#8 Phil Rudin

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Posted 18 July 2014 - 06:47 AM

The newest Zen Underwater port, the DP 170 n85II has the extra extension built-in (30mm) and works like a charm. It will work well with Panasonic 7-14 and 12-35mm zooms, also Olympus 12-40mm, 9-18mm and Sony 10-18mm. Olympus has announced its own "Pro" 7-14mm F/2.8 zoom with the weather sealing and much more coming in the first qtr. 2015, It appears that this lens may also work in the port.

 

Attached is the new port.

 

 

Attached Images

  • P5140151.jpg

Edited by Phil Rudin, 18 July 2014 - 08:02 AM.


#9 Pete L

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Posted 18 July 2014 - 01:20 PM

Definately go for the 7-14mm Pete.
As long as you shoot at F7.1 or above you will have sharp corners.
At F4 it is soft but I am using the Nauticam 6inch dome so your larger dome should work fine.
On land it is super sharp even at F4.

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#10 thetrickster

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Posted 18 July 2014 - 01:37 PM

Thanks my video :)

 

I was purposely flying past rocks to see how well the lens would cope with corner sharpness - yes the 16:9 aspect will help and so too the 4k crop.

 

But I couldn't be happier with it. I have the 12-35mm also - but I think even at 7mm (with the 4k crop) is 'just' wide enough for wide angle shots


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Gear:  GH4, 12-35mm, 7-14mm, 8mm FishEye, 60mm, Atomos Ninja2, NA-GH3, NA-NINJA2, Zen 170mm Dome, Keldan Luna 8 CRI's

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#11 peterbkk

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Posted 19 July 2014 - 02:27 AM

Thanks for the information.

 

Seems like the Panasonic 7-14mm lens is the way to go.