To Jan Crittenden: HVX-200 Green Screen Halo Problem

[Per Holmes]

Hi Jeremy,

Thanks for responding! I haven’t tried that, but tomorrow when it’s brighter, I’ll bring the HVX and a green screen cloth into the edit bay and check it on the Mojo, which I believe can record uncompressed analog? I unfortunately don’t have a monitor in the house good enough to check it directly on a monitor. Unless I’m mistaken, the Avid Xpress Pro/Mojo combination can record uncompressed analog 480i.

But yes, I’d love to find out. I’ll post my results.

Cheers,

Per

[Nate Stephens]

Per,

I am no Tech Emmy winner.. but from what I can see in your photos,,, I am amazed that a camera that cost less than a good HD lens can pull a key that good… Thanks for posting them. I am more encouraged than before.. Yes I can see your enlarged edge defect. But most of my clients don’t study their monitors with a magnifying glass, let alone walk and talk much better than your model. And they are way not that cute….

[Jan Crittenden livingston]

[Nate Stephens] “Jan, can you post that freeze frame of your blonde girl chromakeyed over fire.

I should be able to use it to sleep better and encourage my co-workers that this P2 path is the right path that we are starting on this week.”

Hi if you send me your email address I will send it to you via yousendit.com

I do not have a personal website of FTP server but yousendit works well in these applications.

crittendenj at u..panasonic.com

Best,

Jan

Jan Crittenden Livingston
Product Manager, HPX500, HVX200, DVX100
Panasonic Broadcast & TV Systems

[Jan Crittenden livingston]

[Per Holmes] “Resolution: 1080i/30p
Detail Level: -7
V Detail Level: -7”

Hi,

Not sure why you think the settings for detail should be so soft, but my gut level says that is part of what may be working against you. Detail will help you in defining the edge and basially the chromakey hole that needs to be cut. By taking the detail to such a low place, basically you are working against the process.

Hope this helps,

Jan

Jan Crittenden Livingston
Product Manager, HPX500, HVX200, DVX100
Panasonic Broadcast & TV Systems

[Barry Green]

Per, I don’t know where the fault is in what you’re doing, but I can assure you there are many professionals producing excellent keys from the HVX200.

As an example, when I did training in New Zealand I had the opportunity to speak to the guys from WETA Digital; they conducted chroma key tests between the HVX200 and XDCAM 350. They bought the HVX200.

There’s something happening in the Ultimatte, that’s obvious. It’s not the core image the HVX is generating. And you shouldn’t have to take your detail level down to -7, that’s way too far; Jim Arthurs sets the “sweet spot” for edge enhancement at -3 for bluescreen/greenscreen.

https://www.imageshoppe.com/HVX_bluescreen2.html

How are you getting the footage to key — are you taking the component output? Perhaps the fault is in the d-to-a-to-d process? All the keying I’ve done, and most everyone I know has done, has been from the recorded footage.

[Nate Stephens]

Jan, I tried to send you my email twice, along with a HVX200 thankyou and a SOny HDV chuckle…. I quess I flunked translating email code.. Mine is nate@tvsvpro.com…

[Per Holmes]

Hi Jan,

I’ve done of 70 test shots with incrementally different settings of Detail and V Detail. It only gets worse with higher settings.

Per

[Matthew Mcnulty]

i use a hvx 200, firestore and reflecmedia (chromatte) for my chroma stuff… reflecmedia uses a plugin for FCP called mattinee that works perfectly… you can also use it without the plugin… worked fabulous in AE… no halo… but must stay away from dv25… 50 and above looks great!

[Per Holmes]

Come on, you guys have to give me some credit. Everything is done at the absolute highest resolution.

Upload an uncompressed still of your footage, and I’m quite confident I’ll show you a halo.

Best,

Per

[Per Holmes]

Hi Barry,

I can also assure you that the internet is full of people who get a halo on their HVX green screen footage. On a very regular basis, those people get answers from other people insisting that there’s no halo, uploading footage as proof that CONTAINS A HALO. Fascinating.

I’ve done about 60 separate tests of all combinations of Detail and V Detail settings between -7 and 0, and I can assure you that the halo only increases.

I was previously following the advice you apparently also have been given about -3 being the sweet spot, but that must have been one person’s perceptual feeling. I can say with certainty that -3 is not a sweet spot. It is simply more edge sharpening than -7. I’ll much rather add this sharpening in post, where I can control it. Again, -3 is not a sweet spot, even if that piece of knowledge has propagated over the internet and become ‘common’. I know for a fact that it has more edge sharpening than -7. I’ll be happy to show the pictures if it still matters.

If you’ve read my analysis and looked at the attached pictures, you’ll also know that -7 is in fact truly OFF for the edge sharpening on the LUMA signal. A BW version on a -7 shot yields no edge.

The term to describe this phenomenon is what I would call a Chroma Echo. I have since discovered a specific process that can remove a lot of it by essentially cancelling the echo. In a node-based compositor, I transform to YUV, on a side-chain shift everything two pixels to the left, and blend the U and V channel back ON TOP of the previous signal using what in Fusion is called a Minimum operator, which only adds signal back if it is equal or stronger. That echoes some green in the opposite direction.

This cancels the echo, but also creates a little bit of echo on other edges that weren’t affected as much to being with. A quick garbage matte makes the process more selective. And with a light-wrap or edge-shrink on the parts of the actor that are composited over bright background (procedurally controlled based on brightness), also works great as well.

These are hacks, but they are able to cancel out most of the problem.

As for the keyer, the halo is simply dark enough that Ultimatte considers it to be part of the person and not the green screen. I do get a little frustrated when it’s assumed I’m utterly inexperienced, especially when I’m being this meticulous and scientific about demonstrating the issue.

The problem is also in Primatte and Fusion’s Ultra Keyer.

And no change in lighting has any effect on the halo. I’ve done maybe 50 different lighting tests, front left, front right, side, other side, silhouette, hard light, soft light, up, down, you name it, I’ve tried it. Halo halo halo halo. In every situation.

Thinking it might be come analog capacitance in a DC filter coming right out of the CCD before the A/D converter, I’ve also tried to physically matte the green screen by putting paper in front of the lens so lessen the transition — maybe the circuitry was having trouble with 500 pixels of green before the first edge.

The halo only seems to lessen on edges that are very dark or black to begin with. But all that really means is that the halo blends with the black clothing to become perceptually invisible, it’s easily still there.

Everyone is always talking about how everybody they know is pulling perfect keys. I would like to see those keys. Maybe the actors have been getting an edge-shrink haircut to make it work. I want to see that uncompressed full res footage, only then can we truly and fairly discuss this halo.

Best,

Per