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Must See for GH4 owners - Recovering Super Whites


Julian
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I don't have an external monitor...

What does the Hz setting actually do? Is it related to the hdmi or does it also change something in camera? I think I used it at 24Hz to enable C4K mode. Don't have the GH4 here anymore... had to return my test sample. Have one for myself on order though :)

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I'm confused as to what 24 hz does exactly also. I know that you have to activate it to use C4K. I've emailed SmallHD to ask if they know. Everything works fine with UHD at 24p 60 hz.


Isn't 24hz in cinema 4k mode EXACTLY 24hz instead of 23.976? I'm pretty sure it is. It's because it actually conforms with the digital cinema standard.

In ultra-hd mode it says 24p but it will actually be 23.976 which is needed for perfect three-two pulldown to 29.97 for NTSC.

The easiest thing will be to conform to a 23.976 timeline if possible. This will only slow the speed down by 0.1% so will be imperceptible. The audio will drift short a millisecond every second. So it might start to look out of sync after maybe a 50 second shot or so. But if that's a problem we can just shoot UHD.
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Read speeds still matter though. Obviously the SSD is able to write the speed fast enough from my BMCC so it should be able to be read at at least the same speed.  If i try to edit of my internal HDD i don't get real-time playback 7200rpm is just not fast enough. But if i edit off my external thunderbolt raid array, or even my SSD via USB3.0, i'm fine.  Although all of that is on my iMac, my work laptop is a PC

 

I'm still thinking i should be able to read the 4K 10 bit footage off my SSD. ~700Mbps is well below the maximum read speed of my SSD. 

 

That is certainly a fast laptop, maybe it can play 10bit 4k, god bless you if it does. I converted part of the 4k video to qHD (960x540) 10bit prores, specifically a shot where the camera pans up the fake eiffel tower (love vegas), and you can see it's really jerky. it looks like maybe a sticky tripod.

 

http://vimeo.com/92897851

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I don't know why DVI is getting such a bad rap here.  Dual Link DVI supports 16 bits per channel (48 bit)!

 

Michael

 You're right and it wasn't necessary for me to suggest DVI was crap, just thinking more consumer end but even then dual I suppose is an option and to correct myself again it's actually hdmi from Nvidia vid cards that is the output reduced range RGB not over DVI. DVI to hdmi and visa versa can raise problems though.

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My suspicion is that like the MOV files generated by the GH3, a GH4 set to 0-255 will create files flagged as full-range. THese should be interpreted correctly without clipping either blacks or whites, and help to reduce banding as you have 256 possible values not 220.

 

However, I guess Panasonic is not flagging clips as being full range if either the blacks, or the white are set at 16/235 respectively. Therefore the default 16-255 setting is not flagged as full range in the files, and is being interpreted as 16-235.

 

Just a hunch though.

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Isn't 24hz in cinema 4k mode EXACTLY 24hz instead of 23.976? I'm pretty sure it is. It's because it actually conforms with the digital cinema standard.

In ultra-hd mode it says 24p but it will actually be 23.976 which is needed for perfect three-two pulldown to 29.97 for NTSC.

The easiest thing will be to conform to a 23.976 timeline if possible. This will only slow the speed down by 0.1% so will be imperceptible. The audio will drift short a millisecond every second. So it might start to look out of sync after maybe a 50 second shot or so. But if that's a problem we can just shoot UHD.

 

This is why I'm confused. There are separate fps settings than hz. Why wouldn't a monitor be able to display in 24hz?

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I'm guessing it is a setting relating to monitor display over HDMI to avoid playback jitter on screens that support 24Hz.

 

 

Edit: It also seems that according to current standards 4K can only be transmitted over HDMI at 24Hz, whereas UHD can/will go higher in the HDMI 2.0 spec.

 

Edit2: Having looked at the GH4 instructions, 24Hz (Cinema), 50Hz (PAL) and 59.94Hz (NTSC) are just system frequency settings to keep recording framerates divided into their specific regions.  4K records at exactly 24fps (only available in 24Hz mode) whereas UHD can record at 23.98fps, 24fps, 25fps or 29.97fps depending on what the system frequency is set to.

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