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dreifish

Member Since 25 Oct 2013
Offline Last Active Jul 20 2017 06:23 AM
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Posts I've Made

In Topic: Panasonic LUMIX GH5 for underwater video

20 July 2017 - 03:07 AM

 

Richard, you can do Kelvin tuning on the GH5 natively.  Put on the RGB overlay on the DNC and you get the same tool - maybe not as effective as with the Atomos, but it works  (see Kelvin in upper right corner with up and down arrow to adjust)

 

Is the overlay at the bottom of the screen generated by the DNC monitor, or by the GH5 itself? Does the DNC have any options for displaying false color or zebras (for exposure)? How about peaking/punch-in and/or other focus aids?


In Topic: Panasonic LUMIX GH5 for underwater video

20 July 2017 - 03:03 AM

 

 

Are you sure you looked at the DNC-7A back then?  They have updated the DNC-7 to DNC-7A a while ago, but I dont think it was four years ago but I may be wrong - tiem goes bye fast...  Easiest would be for you to ping Alex at diveandsee. I am sure he'll give you some more on his plans.

 

Burkhard

Might've been the DNC-7.. I think it was right around the time of the DNC-7A release though. So let's say 3 years ago :)

 

 

 

Richard, you can do Kelvin tuning on the GH5 natively.  Put on the RGB overlay on the DNC and you get the same tool - maybe not as effective as with the Atomos, but it works  (see Kelvin in upper right corner with up and down arrow to adjust)

 

Interesting! So in the manual adjustment mode, how high can you push the Kelvin temperature? Past 10000k? Does doing a custom white balance off a white slate let you boost the reds further than just entering the Kelvin temperature manually?

 

EDIT: Just saw your answer above. 9900k sounds like the same limitation as on the Sony's. But perhaps you can actually achieve a higher Kelvin temperature using a custom white balance off a slate at depth. 


In Topic: Panasonic LUMIX GH5 for underwater video

20 July 2017 - 01:50 AM

[t-quote name="bubffm" post="385952" timestamp="1500415520"]

I'm not a technical expert by any means but the way I understand it, is that any white balancing at depth, whether manual or automatic, will introduce a certain amount of noise, because effctively you are 'artificially' inreasing the red channel - and that will add more noise to that channel, because by white balancing you are not adding any more information to that channel. Things should be better in 10bit because of the addl. color info compared to 8bit, so I am having good hopes in the GH5 in that respect
Whether there is more noise introduced on a Panasonic compared to lets say Sony I dont know. But I can tell you from my time with the Sony AX100 camcorder it was introducing plenty of noise if you where below 15 meters on ambient light only. I guess thats just a critical depth fo most cameras where they start to struggle.[/t-quote]
 
Right -- what you're essentially doing when you're white balancing at depth is telling the camera to apply gain to the brightness levels recorded by the "red" photoreceptors. So it's equivalent to boosting the ISO, and will make any existing noise in the red channel more apparent. With the GH4, the noise was quite visible/distracting when trying to white balance around 20 meters (especially if your base ISO was already 400 or 800 to account for the lower light). 
 
This step happens before any of the data is encoded into an 8 bit or 10 bit video file-- white balance is processing applied to the 12 bit data coming right off the sensor. So the final recording format isn't going to make a difference to the amount of noise. The GH5 should still be better overall then the GH4 simply on account of newer sensor technology, using a larger area of the sensor for video and better noise reduction, but the differences are probably similar to the overall improvement in low light performance. DXOMark rates the GH4 and GH5 as essentially identical in terms of noise performance, so I wouldn't expect the GH5 to be significantly better than the GH4 in terms of noise when white balancing. A full frame camera like the 1DX Mark II should be 1-2 stops better, which is what the Backscatter guys seem to report as well.
 
As to whether a 10-bit 4:2:2 h.264 file will make it easier to correct a bad white balance in post than an 8-bit 4:2:0 file h.264, it might make a bit of a difference, but it won't be night and day like you would get if you were recording raw. During the encoding process that creates the h.264 file, the 12 bit data in the red channel is going to first get confounded with the signal from adjacent blue and green pixels as part of debayering. Then it's going to get compressed from a 12-bit space where 4096 gradations of brightness can be represented to a 10-bit space that only supports 1024 gradation. That alone throws away 75% of your data. Then you end up throwing away the color data for half the pixels when you go from 4:4:4 to 4:2:2 color. So you're already down to 12.5% of the original data (not accounting for errors introduced by debayering based on the wrong white balance) before you even get to the compression stage. Then you add the fact that h.264 compression tends to preferentially eliminate data in the shadows. Your red channel underwater is mostly going to contain data in the shadows if it's not pre-boosted by a "proper" white balance before this stage is reached.
 
So yeah. If you want to retain information in the red channel when shooting in a compressed video format, you need to make sure that the data is properly baked in by a good in-camera white balance. Since the red channel signal is going to be very weak coming right off the sensor, if you don't boost it significantly before recording it (and more importantly, compressing it substantially using h.264 compression), you'll end up trying to reconstruct what should be dozens of shades of red of various brightness from very little data indeed. 
 
All of which is to say that, when recording to any sort of compressed RGB or YUV codec underwater using only ambient light, the camera's ability to do a proper white balance in the 40000-50000 kalvin range with significant magenta push is far more important to the final result than the bit depth or color depth of the recording codec.  Good white balance flexibility will get you nice colors even in a 8-bit, 4:2:0, low bitrate codec. Case-in-point: canon dslrs. Whereas if your camera won't let you set a white balance higher than 9900 kalvins (e.g. all Sony mirrorless cameras that, and maybe some of their cinema cameras too), the codec won't matter. At least, not unless you can record the raw sensor data before debayering and compression.

In Topic: Panasonic LUMIX GH5 for underwater video

19 July 2017 - 11:05 PM

Interes

 

Andrei, this is the the link to the 7'' equivalent: http://www.diveandse...nitors/dnc-7ah1

 

The 7'' sells for USD 2650 incl. bulkhead, cables etc.  The new 5.5'' is less - but not by much.  As I have a pre-release version I don't want to talk about my price as I dont want to preempt what they may later put on their webpage as official price. Not a super bargain but you get an extremely solid and rugged piece of gear.

 

The 5.5'' is already a HUGE screen compared to the build-in 3.2'' of the GH5. If there would have been a lighter 5' version, I might have even taken that.  Its not just the size itself, it's the much better viewing position having a monitor on top rather than that build-in LCD at the lower end of the camera housing.

 

7'' would be too big for me (and I am wearing optical glasses in my mask), but thats why there are different sizes :)

 

NB: Whether they make a new 7'' version you'd have to ask. I think the 7A is actually pretty new and may have the same specs inside (apart from screen size) The layout of the buttons and the menu operation (press-and-turn-wheel) has changed somewhat on the new smaller version.

Ah.. the 7A has definitely been around for a few years now. I remember looking at it at Backscatter maybe 3-4 years back now. Was hoping they'd updated it.

 

Still, the price seems to have gone down a little bit. All things considered, it's probably about half what you'd have to pay for a housed Atomos Shogun, so it's tempting. Just not sure about the quality of the display and tools available on it compared to more standard offerings from Atomos or SmallHD. But definitely a win when it comes to bulk, it seems! Part of me wants to go with the Atomos/Nauticam housing to also get the option of 10bit 4k60p recording in a slightly more robust prores codec, as well as the brighter screen and ability to use it on land. 

 

I agree with you that a 5.5" monitor that you can position is already a great improvement over using the internal screen, but for critical focus and framing at 4k+ resolutions, I've never heard anyone complaining that a monitor was too big :) I suppose a lot depends on the boyancy and trim characteristics though. If the Atomos makes the Gh5 really negative or back heavy or impossible to operate well, then I guess it's a no-go.


In Topic: Panasonic LUMIX GH5 for underwater video

18 July 2017 - 04:34 PM

tbh, I think those Komodo shots are, well, average. Poor white balance, and yes its mostly fisheye. The Backscatter clips are so much better. Almost looks like footage from a RED.

The DNC-5A turned out heavier than I thought, but the size is perfect for the GH5.

 

Bubffm, how much is the DNC-5A selling for? Are they also making a new version of the 7" monitor? I really need to get something, and, with my aging eyes, I'm thinking the benefits of 7" might outweigh the size disadvantage..