7" Video Assist HDR Color shift still an issue? 3.1

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rick.lang

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7" Video Assist HDR Color shift still an issue? 3.1

PostThu Mar 11, 2021 8:09 pm

The UM4.6K has the Film to Video LUT selected but not applied anywhere and the Dynamic Range is always Film. Display 3D LUT is always Off everywhere. There’s no option in firmware 4.8 to explicitly record a LUT in the file as there is on the BMPCC4K for example.

Clean Feed was set On for the SDI Out; I used both On and Off as mentioned in the previous post just to see if the Zebras on the BMVA12G7 matched the camera as they did.
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Jamie LeJeune

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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostThu Mar 11, 2021 8:52 pm

Rick, just to clarify, the image appearing on your BMD Video Assist is the low contrast image of BMD Film, yes?
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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostFri Mar 12, 2021 4:18 am

Further test shows the red tint although greatly reduced is still there. Unlike before its now less pervasive and can at least see other colours more easily and differentiate what should be white unlike before. It looks like it has boosted the blue and green channel against the already high red channel. I wish another firmware will try and reduce the red or magenta a bit further or include a "Tint" option like they have in their cameras.
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7" Video Assist HDR Color shift still an issue? 3.1

PostFri Mar 12, 2021 5:26 am

Jamie LeJeune wrote:Rick, just to clarify, the image appearing on your BMD Video Assist is the low contrast image of BMD Film, yes?


Jamie, yes the image is set to use Dynamic Range Film without LUTs applied.

BMVA12G7 has the 4.6K Film to Video LUT selected, but Display 3D LUT is Off. The UM4.6K has Clean Feed On for 12G SDI. THE 4.6K Film to Video LUT is also selected on the camera but Display 3D LUT is also Off. Zebras are identical.

This is the way to ensure the camera and the BMVA12G7 are independently calculating their respective Zebras based on the clean feed.

The UM4.6K LCD has Zebras On and Clean Feed Off so I can see the camera Zebras. For the Front SDI going to the BMVA, I can have Clean Feed On (or Off and all other camera options Off), so I’m using the BMVA to generate Zebras and they look the same as the camera LCD Zebras and the BMVA12G7 Zebras. Same sensitivity to changes in my iris.

I was surprised to see False Colour variations on the BMVA12G7 which is peculiar because the Zebras are consistent. Sometimes I want to see False Colour while shooting outdoor events under changing light conditions; I have used the camera LCD or the BMVA with False Colour (to maintain pink and green skin) a few times that way but I’ll use the BMVA12G7 Zebras for clipping while the larger and brighter image is good for framing and focus.

It’s been a learning experience going through these options and it also reminded me what a capable camera the UM4.6K is while I’ve mostly shot with the BMPCC4K in the last year. So glad the older camera is functioning very well for the ways I use it: 4608x1920 and 3840x2160 with the 1.33x-65 Anamorphot for client shoots. Only option I have to record CinemaDNG lossless or ProRes 444 XQ for special occasions. Knock on magnesium (but gently, eh?).

To do the tests today and have both cameras feeding HDMI and SDI into the BMVA12G7 and monitor either camera with one button to select the HDMI or SDI feed is nice. I’m thinking if the music festival happens this year I could use both cameras for different angles and monitor both via the single BMVA12G7 since SDI can run a good distance. Let the UM4.6K and my assistant capture more of the stage and shoot with the BMPCC4K to handle the performers’ closeups.
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Jamie LeJeune

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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostFri Mar 12, 2021 6:55 am

Ah, so false color is looking different while Zebras aren't. That is the crucial clue here which, I think, cracks the case.

Rick, I'm fairly sure the difference between what you're seeing and what Mark and I are seeing with our setups is because:

1) In Gen3 (and Gen4) of BMD film on the original 4.6K, the log curve isn't nearly as flat as Gen5 in the UMP 12K that Mark and I are both looking at.
2) The Zebras on the Video Assist operate in large increments, they don't clearly show differences less than 10%.
3) The false color has smaller increments, especially at the top so differences there do show up.

Your camera and Video Assist are working exactly the same as ours — the zebras you're seeing are reading the log signal as any other monitor would rather than reading any kind of direct metadata from the camera, it's just that the Gen 3/4 curve is not so flat. So, the zebras on your Video Assist will look similar enough to those on the camera LCD but when viewing the false color on the Video Assist it's clearly different from the false color on the camera LCD. While, for Mark and I who are viewing BMD Film Gen 5, the curve is so flat that even the Zebras look markedly different from the camera LCD because they don't get triggered until much lower in the scale with that flatter Gen5 curve.

And, that would also explain why Mark remembers it being different before he had the new 12K, as before that he would have been sending out the less flat BMD Film Gen3 or Gen4.

In other words — Nothing has changed about how the camera and Video Assist read signals for false color and zebras. All that has changed is relative shape of the log curve between BMD Film Gen3/4 and BMD Film Gen 5.
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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostFri Apr 02, 2021 7:18 am

I just updated to firmware version 3.4.1 and straight away the red or magenta cast was pretty bad, about as bad as it was with the firmware before the previous one before it had the first colour correction. After leaving it on for awhile and switching it off and on the red cast slowly lessen. Not saying the red cast is gone or if it improved over previous version. I don't believe the VA need a warm up to correct the colour cast but it did needed a run-in period with the latest firmware to get settled.
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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostFri Apr 02, 2021 6:33 pm

Interesting observation. Thanks for the suggestion.
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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostFri Apr 02, 2021 7:16 pm

Going against what I previously said I think the VA does need a few minutes warm up for the red/magenta cast to recede slowly. Its not completely gone and still look a bit warm but certainly look less red/magenta than when start up from cold.
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Re: 7" Video Assist HDR Color shift still an issue? 3.1

PostMon Apr 12, 2021 4:39 pm

Ah, I posted an new thread without seeing that this thread is pretty recent. Anyway, I just bought the Blackmagic Video Assist 12G 7" and was massively disappointed to see a pink tint on it. I was using the older 3G version of the same monitor and I was extremely happy about that monitor.

Also, like someone mentioned here before, the pink cast only seems to be on the video signal coming from my BMPCC4K. The text and the other graphics that's inherent to the monitor is perfectly fine. God! I hope they solve this. This is a really expensive piece of kit and I really hate to be running around trying to return and alll that hassle.
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