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#221 Raptor^

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Posted 10 July 2014 - 12:22 PM

What do you guys who have the GH4 think of the video autofocus? I have seen a few tests on it and to be honest it really looks like sh*t. Extremely slow and hunting very much compared to the tests I've seen on the GH2 and the GH3. The GH3 seemed to have much faster autofocus and more precise than the GH2 which also was great, but the GH4 seems to have taken a giant leap in the wrong direction?

 

Here is just one example of it not even being able to track a person walking towards the camera.

  Autofocus test at 25:09

 

GH4 vs 70d autofocus, again the GH4 is really slow.

 

And to compare, under is a GH2 vs GH3 autofocus test; much faster! 

 

Finally Griffin Hammond with his GH3 vs GH4, take a look at 06:28.



#222 thetrickster

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Posted 10 July 2014 - 11:06 PM

What do you guys who have the GH4 think of the video autofocus?

 

Personally, I was all agitated by Nautilcam releasing a 6" Dome with MF knob, while I was putting my GH4 Rig together - I have the Zen 170mm one, and I did also read about the relatively poor AF compared to the 70d etc.. so was too thinking have I made the right choice

 

But on actually diving with the thing and having it set to S-AF and f5.6 - I see no reason to use C-AF/MF underwater. the hyperfocal distances for the m43 lenses are pretty extreme for these apertures so everything from 3m to infinity will be in focus, so focus on something 3-4m and hit record - all is good.

 

Also I would note that, the video above comparing it to a 70d isn't really a fair comparison.

 

Its using the Olympus 60mm - which a) is pretty awful for AF on its own b) Doesn't benefit from the 'Depth from Defocus' which the GH4 can utilise with Panasonic lenses


Edited by thetrickster, 10 July 2014 - 11:11 PM.

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#223 textilet

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Posted 11 July 2014 - 07:15 AM

This chart http://www.dofmaster.com/dofjs.html has the hyper focal distance at about 2 ft for 7mm@ f/5.6 (assuming the numbers are similar underwater and through a dome). 3m actually had me a little discouraged given my local visibility ☺

#224 dreifish

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Posted 11 July 2014 - 09:43 AM

This chart http://www.dofmaster.com/dofjs.html has the hyper focal distance at about 2 ft for 7mm@ f/5.6 (assuming the numbers are similar underwater and through a dome). 3m actually had me a little discouraged given my local visibility ☺

 

I think the virtual image with domes might throw all those calculations out the window. If I understand dome port theory correctly, the virtual image created by the dome of a subject at infinity, will lie in a position which is 3 x the radius of the dome (ROD) in front of the front surface of the dome. Subjects closer to the dome than infinity will have a virtual image closer to the dome.

 

So if the ROD is 7", that means the furthest your lens would need to focus is 21" in front of the dome. If you're prefocused on the hyperfocal distance so everything from 2 feet to infinity is in focus, you'd basically have none of the virtual image in focus. 

 

Can anyone elucidate how dome theory impacts hyperfocal distances? Does it mean that to have everything sharply in focus you just need the zone from the front of the dome (i.e. ROD) to 3XROD in front of the dome in focus? Or do you need the area from right in front of the lens to 3XROD in focus?


Edited by dreifish, 11 July 2014 - 09:55 AM.


#225 Interceptor121

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Posted 11 July 2014 - 10:23 AM

In a thin glass case the focus point is actually 4xr so for a 7" dome would be 14" this means your lens minimum focus distance on land has to be less otherwise you cannot achieve focus.

In reality as the domes are thicker the requirements are for shorter minimum focus distance.

The effect of aperture in a dome is more to control diffraction in the corners (smaller dome needs smaller apertures) and brightness than to actually control hyperfocal distance in the traditional sense as the port is not anymore flat each dome hits a certain f/stop that produces optimal results if you go wider the corners are blurred. Larger domes lower f/stops

The 7-14 Panasonic has a 25cm minimum focus distance hence smaller dome is 5" in case of a perfect thin glass, Nauticam want to make sure the apertures are not too small so they go to 7" as probably 9" won't work with the form factor of the lens camera.


Edited by Interceptor121, 11 July 2014 - 10:36 AM.

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#226 dreifish

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Posted 20 July 2014 - 10:03 AM

I'm going to be picking up the GH4 in the new Nauticam housing and I'm looking into lens options for video (topside and underwater). Because I will be using this for travel, I'd like to keep it to as few ports/domes as possible. I need some advice, especially on how to optimize ports and extensions to keep travel size down so ports/domes can be put to multiple uses. Sorry for all the questions! Maybe I should split them out into several posts.

 

1. For wide angle work, I think I prefer the look of the 8mm fisheye to the rectilinear lenses for more "dramatic" shots, especially with the 2.4x 4k crop. My understanding is that this lens only works in the Nauticam 3.5, 4.33 and Zen 100mm domes (not the larger 6 inch dome, the 170mm zen or new 180mm Nauticam glass dome. Is this correct?

 

2. Can any of the small domes (Nauticam 4.33"/Zen 100mm) be used with the 9-18 or 7-14 using extension rings (and diopeters?) I'd like to minimize my travel kit.

 

3. Are there any issues with using the 8mm for video with a 2.4x crop aside from finding enough lights to evenly light the scene? What angle of coverage would the 8mm have with the crop? Basically, it would behave like a 19mm fisheye on full frame/13mm on APS-C?

 

4. Would you recommend the 7-14 or 9-18 for wide-angle rectilinear video?

 

5. I will probably also pick up one of 12-35, 12-40 or 12-50 for topside use? Are any of them (more) useful for underwater video? I'm thinking of potentially using them for establishment shots (wide->medium->narrow) when filming macro or for shy sharks, fish portraits. 

 

6. Does the 12-50 do anything that the 12-40 couldn't? Seems like macro on the 12-40 is almost as good -- but how about port compatibility? Which domes/ports would the 12-40 work with?

 

7. For macro/super macro, I will probably pick up the Olympus 60mm. Any point in also getting the Panasonic 45? Or would pairing up the Olympus with the 12-50 make more sense? 

 

8. Assuming I choose to go with the 60mm & 12-50, any disadvantages to housing them in the dedicated Nauticam 12-50 port vs the 60mm port?

 

9. What wet diopeter should I combine with the 60mm for super macro? I understand that in 35mm equivalent terms, it's already 2x -- so I would get twice the magnification I'm used to from the 105mm on Nikon FX for the same size "print" or display. In fact, with the 2.4x 4k crop, it's going to be 2.4x equivalent magnification, yes? Is adding a Nauticam SMC way too much? Does the depth of field became unusable for macro video work?

 

10. What tripod/steadying solution can be used for macro video?

 

11. For those who already have the NA-GH4 housing, what's the buoyancy like? My NA-D800 was almost perfectly neutral with a dome, but the RX100 setup was quite negative with wet lenses.   Does the GH4 need to a number of floats?How should they best be configured to keep the system steady for wide angle video?

 

12. I will probably get the Atmos Shogun as a monitoring/recording solution once it's out and there's a housing for it. In the meantime however, are there any housed monitors larger than 4" that can be used with the GH4? Or is the DP4 in Nauticam housing the best current solution if all I want is a monitor?



#227 kc_moses

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Posted 21 July 2014 - 07:15 AM

8. Assuming I choose to go with the 60mm & 12-50, any disadvantages to housing them in the dedicated Nauticam 12-50 port vs the 60mm port?

 

 

10. What tripod/steadying solution can be used for macro video?

 

I'm going to give opinion for these two questions since I'm on the same boat of considering the GH4, while waiting for the Panasonic LX-8 to release before I pull the plug. During my research of the GH4 I came across some answer of my own that might relate to you.

 

For question 8:
I'm not sure if you could house the 60mm lens into the $800 Nauticam 12-50 port (NAU.36162). You can house the 12-50mm lens into the $300 60mm port (NAU.36163) with an aftermarket $120 zoom gear (cheaper if you use 3D printer to print it). This however won't give you access to the 43mm macro feature of the 12-50mm lens. The 12-50 Nauticam port is 77mm thread, while the Nauticam 65 port is 67mm threat. So people use Subsee +10 or the Nauticam SMC on the 67mm threat to get good macro. 77mm wet lens flip holder is another $300 or so. Therefore the 12-50mm port route is very expensive.

 

For question 10:

Look up "Xit 404" tripod, the 3 legs point is the way to go. I played around with cheap attempt of using a Gorillapod, since there is only one point under the camera and the center of gravity will be off depends on your arm/light/strobe configuration, Gorillapod is not a good solution for bigger set up (will work from things like goPro).

Since you're outputting 2.4K from 4K, you have the advantage of stabilize the footage in post and still not loose quality because you would have plenty of pixel to crop. So, no need tripod for now unless you want to output to 4K.

 

Since you're doing video, the Panasonic G X 12-42mm may be a contender as it has Power O.I.S, electric power zoom, low profile. However, some said the sharpness is not as good compare to things like Sony RX100 base one some data from DXOMark website. This is where you can do more research, but at least at this point you would just narrow down to less lens.

 

Hope that help!

 

Moses



#228 Interceptor121

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Posted 21 July 2014 - 08:25 AM

I think you need to be a bit careful when talking about crop factors of 2.4x

The field of view is evaluated on the diagonal so it looks like the lens will be 19.2mm equivalent

 

However the crop is only on the vertical axis so the horizontal field of view does not change.

Once you add an electronic stabiliser this will start reducing the field of view accordingly meanwhile the lens will still have plenty of barrel distortion typical of fisheye

 

Going to the other point I personally do not like fisheye lenses for video the 7-14mm lens is sharper than the 9-18mm that is much cheaper however if you had to crop say 1.15x in post the wider lens would be better

 

In terms of lenses the only options when I looked at it to minimise the number of ports were

1. Get 6" dome with 7-14mm and 12-35mm OIS (you want a stabiliser at those focal lenghts for sure) you will then need a macro port as well

2. Get the 14-42mm with 35 macro port and use wet lenses, results optically not as good as 1 above but easier to travel with you do add a number of wet lenses

 

Option 1 has better IQ option 2 is more portable

 

Using ports not designed for the lenses could result in the lens not focussing at all worse case or poor performance in others


Edited by Interceptor121, 21 July 2014 - 08:25 AM.

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#229 SimonSpear

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Posted 23 July 2014 - 03:51 AM

Some 4K underwater footage from the GH4.  
 
This was uploaded overnight on the slow hotel wifi so it is a bit short, but still I'm very impressed (obviously for the best quality playback select the 4K option, but some computers won't be able to handle it).
 

Edited by SimonSpear, 23 July 2014 - 03:52 AM.


#230 peterbkk

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Posted 23 July 2014 - 04:26 AM

 

Some 4K underwater footage from the GH4.  
 
This was uploaded overnight on the slow hotel wifi so it is a bit short, but still I'm very impressed (obviously for the best quality playback select the 4K option, but some computers won't be able to handle it).

 

 

Thanks for sharing.

 

As always, even at 4K, YouTube compression messes it up.  Blocky artefacts appear in the blue.  Vimeo does a better job at HD than YouTube does at 4K.

 

What about the colour?  Were those colours close to what you saw with your eyes?  

 

What did you do for colour correction?  In camera?  In editing?

 

The blue background looks at bit purple to me.

 

Regards

Peter



#231 SimonSpear

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Posted 23 July 2014 - 01:45 PM

This clip was straight from the camera.  The codec is pretty robust so I'm sure you could make the turtle pink with green spots if you know how to do it, but why would you want to make it look like your eyes see?  If you want that there are plenty of less expensive cameras that can do it!



#232 textilet

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Posted 23 July 2014 - 01:54 PM

Nice Simon- red filter or just white balanced?

#233 ScubaBob

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Posted 23 July 2014 - 02:31 PM

This clip was straight from the camera.  The codec is pretty robust so I'm sure you could make the turtle pink with green spots if you know how to do it, but why would you want to make it look like your eyes see?  If you want that there are plenty of less expensive cameras that can do it!

 

Well said Simon - I think the footage/color looks great!!


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#234 kc_moses

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Posted 23 July 2014 - 05:15 PM

I too like that deep blue color. Did you shoot with CineV color setting?



#235 peterbkk

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Posted Yesterday, 10:35 PM

[quote name="SimonSpear" post="350723" timestamp="1406151900"]This clip was straight from the camera./quote]

Can you please share your camera image settings with us.

Regards
Peter

#236 Interceptor121

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Posted Yesterday, 11:50 PM

Looks very similar to my deep sunset red filter

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