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GH4 DR on external 10 bit 4.2.2?


paulraymaekers
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10-bit 4K external recording will be possible with the Shogun (September) or quad SDI recorders (possible now with YAGH: http://www.bhphotovideo.com/c/product/857190-REG/AJA_KI_PRO_QUAD_Ki_Pro_Quad.html).


Thanks. But a solution that cost 2x more than my camera and lens doesn't look very justifiable at the moment. Is there a rumoured price for the Shogun?
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Just to clarify what I said above, the footage was shot at 4K on the GH4 but recorded to the Ninja as 1080p. I have no idea if you will get superior results recording 10-bit/422 4K to a Shogun and then downsampling in post. I don't see why you would really.

 

Doesn't downsampling via the Ninja just simplify the workflow? Is it possible that the big wait for the Shogun will be a bit pointless if you're going to be downsampling to HD in post anyway?! Personally I'd rather have a Ninja Star in my pocket than a Shogun on top of my GH4 ...

 

 

hey matt--

 

I was doing a test with the GH4 footage and I noticed that the fine hair started to show symmetrical scanlines when you push the luma (this was done by raising the blackpoint and isolating the green channel), so I zoomed in to look closer.. this must be the Ninja Blade downsampling from 4k? it's the GH4 outputting 1080p. I think this answers the question as to why someone might want to shell out for the Shogun, capture 4k 10bit and reformat to HD in post. I put up some Alexa footage just to show something with the same luma tweak and zoom so you can see it's not happening in the resize etc.

 

The Alexa footage was very shallow focus, so the hairline is a little soft (and a lot less hair!). I know they are very different price points too. 

 

 

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Guest d5f8611fa423d0e628c016f9d5c93b47

I don't know how the Ninja Blade records the 24p footage - is it possible that this is interlacing? e.g. due to the Blade putting the 24p in a 50i/60i wrapper or something? I really don't understand the tech well enough. If it is interlacing, will the Star have this same issue? Not that I'd call it an issue really - your clip is zoomed 1000%!  :D Lots of question marks still about this, but even if the footage isn't pixel perfect we know it's possible to get stunning footage that is a pleasure to grade with just a GH4 and a 1080 Ninja. 

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Yea, it looks good for the price for sure :)

 

The scanlines don't look perfectly horizontal like fields, they seem to curve and go vertical in places. Not sure what the exact method is.

 

Would be good to compare 2k out instead of the 4k and see if the GH4 downsampling is better. 

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Guest d5f8611fa423d0e628c016f9d5c93b47

Would be good to compare 2k out instead of the 4k and see if the GH4 downsampling is better. 

 

Is the GH4 output signal still 10bit 422 if you shoot at 1080 though? Anyone?

 

Based on what we've seen of the GH4's internal 1080 I'd imagine it won't be any better anyway, but I 'm sure someone will test it (eventually).

 

Hopefully a moire/aliasing test will be done by Andrew when he looks into all this ...

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Jacob Neilsen posted this 10 bit footage from GH4 + Ninja Blade via Dropbox (see EOSHD's GH4 Review comments thread, page 3): 

 

https://www.dropbox....est footage.mov

 

I put it into FCPX and pushed it around a bit and was amazed (never worked with 10 bit before though!). I think it looks absolutely stunning - particularly the 2nd shot of the girl with the chair.

That is ridiculous (in a good way).  :)  Wow!  It's like a whole different camera!  Color, dynamic range, the entire look is better, and it was good before.

 

If you get any more examples, please post them.

 

Michael

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Here is 10bit 4k example (external). I can upload original file (downloaded from vimeo, 12GB) to copy.com if anyone is interested.

Another good clip, although I am seeing some judder and aliasing in a few place (perhaps during the downconversion there is some line skipping?).  Regardless, it's clear 10 bit 4:2:2 really bumps up the quality.

 

Michael

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hey matt--

 

I was doing a test with the GH4 footage and I noticed that the fine hair started to show symmetrical scanlines when you push the luma and zoom in.. this must be the Ninja Blade downsampling from 4k? I think this answers the question as to why someone might want to shell out for the Shogun, capture 4k 10bit and reformat to HD in post. I put up some Alexa footage just to show something else at the same luma tweak and zoom.

 

The Alexa footage was very shallow focus, so the hairline is a little soft. It just shows the lack of scanlines. 

I examined the original GH4 422 10-bit clip in PPro with contrast at 200 and brightness pulled down: the hair is perfectly fine- no sampling issues, about as perfect as is possible. I don't see an issue with your clip either- it looks normal once contrast is cranked and effective anti-aliasing has been removed. The Alexa clip wasn't the same kind of image to compare against.

 

I don't see anywhere that the Ninja Blade has a 4K to 2K scaler- where is this information published? The GH4 has a 4K to 2K scaler on the HDMI output (I tested it and it looks great).

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Is the GH4 output signal still 10bit 422 if you shoot at 1080 though? Anyone?

 

Based on what we've seen of the GH4's internal 1080 I'd imagine it won't be any better anyway, but I 'm sure someone will test it (eventually).

 

Hopefully a moire/aliasing test will be done by Andrew when he looks into all this ...

I haven't tested 1080p with 10-bit 422 enabled, however 4K 10-bit 422 scaled to 1080p by the GH4's HDMI scaler looks great.

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Guest d5f8611fa423d0e628c016f9d5c93b47

Yea, it looks good for the price for sure :)

 

The scanlines don't look perfectly horizontal like fields, they seem to curve and go vertical in places, so I think it's just a very symmetrical downsampling algorithm that the Blade uses to be able to capture in RT. Not sure what the exact method is.

 

Would be good to compare 2k out instead of the 4k and see if the GH4 downsampling is better. 

 

I forgot about this other test Jacob did. It answers your question pretty comprehensively I think!

 

 

pw: aliasing

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Guest d5f8611fa423d0e628c016f9d5c93b47

My number one wish for this setup has nothing to do with image quality though (I'm already sold on that I think). The thing I'd like to see most is a secure way to connect the HDMI cable from the GH4 to a Ninja. There is enough duct-tape in my life already   :angry:

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matt-

 

Yea, it kinda does answer the question. Based on that test, since 8bit 4k downscaled in post seemed to be the best for killing moire, 4k 10bit downscaled in post to 2k should be even better, but what a waste of space.

 

It seems like the hardware based undersampling is best to avoid.

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Just got a hint that my GH4/NinjaBlade tests were discussed!

 

Yes - it's NOT the Ninja Blade downscaling. The scaling appears on the HDMI output side of the GH4, and I think the GH4 does this scaling extremely well. I wanted a quicker workflow than internally 4k/8bit>downscaling in Premiere and more edit friendly files from start. If you watch my moiré test, you would perhaps still want to record 4k internally and downscaling in post if you want the most moiré-free result, but those tests were setup to absolutely worst-case-scenario. So I think the choice to record 4K internally or to use an external recorder to get those lovely 10 bit ProRes files from start depends on either dealing with a more heavy and not-so-discrete rig setup in recording or dealing with the more heavy post workflow downscaling those 4K H264 clips. They don't run very smooth on my timeline, where as we all now those prores files just play like a joy! 

 

One issue however: It seems that you will only be able to record a true progressive signal if recording mode is set to 24 Hz. I hope this will be fixed in upcoming firmware updates from Atomos. If recording from especially 50 Hz in PAL mode, GH4 always will send an interlaced signal, (and only in AVCHD mode), and no matter how I interpret those files in Premiere, they don't look as nice as 24p. Perhaps others have tested this and got better results?

 

Best, Jacob.

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Ahh, so it's the GH4 that is undersampling.. I read this:

 

 

Some ungraded tests for you to examine. UHD/HDMI 10 bit > Ninja Blade ProRes HQ. 

https://www.dropbox.com/s/9mt8hkrfk6hepj0/GH4%20UHD-Ninja%20Blade%2010bit%20test%20footage.mov

 
it sounded like you were outputting UHD from the camera. 
 
just found this:
 

1. Does the GH4 output 4K over the micro-HDMI port?

When the camera is set to record in 4K internally the onboard HDMI output is down-converted automatically to 1080p. In playback mode the HDMI output is 4K capable (relaying the 8bit 4:2:0 footage from SD card). Only the DMW-YAGH add-on base can output 4K (uncompressed, 10bit 4:2:2) from the GH4. However the micro-HDMI port is 8bit / 10bit switchable and can deliver impressive 1080p in 10bit 4:2:2 format, uncompressed to an external recorder.

 

 

So if this is correct, the Atomos Shogun will be recording 4k 8bit 4:2:0 from the GH4 through the micro-HDMI port, and limited to the size of your SD card?

 

confused.

 

 

 

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Ahh - I see the confusion now because wasn't clear in my description.

 

Camera menu says:

 

HDMI Rec Outpu t> 4K Down Convert > Auto/1080p/off

 

It was set to 1080. If set to OFF, it doesn't receive a signal, so Ninja Blade is not compatible with an HDMI 4K signal.

 

Be aware that the 4K > 1080p scaling on GH4 introduces a pronounced delay - I would guess around 1/2 a second or 12-14 frames. So for action related shots, I would guess it could be an issue. I'm using it for static concert filming, so I guess I will be getting used to this delay. Focusing feels a little sluggish though.

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