To Jan Crittenden: HVX-200 Green Screen Halo Problem

[Vince Becquiot]

Per,

Looking at your grab, I think what you are seeing is simply chroma subsampling, and that’s in the compression scheme. Let us know how you do with component out.

Vince

[Marcus Van bavel]

Looking at your first example, the fringe is caused by the 4:2:2 chroma signal not being filtered properly. I don’t suppose you use Raylight? Raylight makes better keys because of the chroma filtering in the full raster format, you can use it with After Effects and other programs (in Windows). Raylight for Mac on the other hand will not help since it uses the Apple codec which does not filter chroma.

[Per Holmes]

Hi,

Thanks for responding. I have some good news, which is that indeed Panasonic’s DVCPROHD decoder does not do any chroma filtering and Raylight does, so it looks much better in Raylight (see below). I should add, though, that NOT doing chroma filtering is not a bug per se, and I’m perfectly able to do my own chroma filtering in post. This is similar to the “Matrox Bug’ back in the DigiSuite days, which wasn’t really a bug, but more an omission, deliberate or not.

I’m quite happy with what raylight does so I think that’s certainly something to get.

The halo is not gone, though, just more blurry:

https://www.hollywoodcamerawork.us/hvx/still_raylight.png

And here it is composited in Ultimatte. The keying consisted of selecting the backing color and then doing a single ‘Add Matte’ on her face to bring up the matte density. So not a carefully done matte, but with exact same settings as before.

https://www.hollywoodcamerawork.us/hvx/still_raylight_composited.png

I think that definitely the composite looks better with chroma filtering, which interestingly enough, Ultimatte wouldn’t do even when it was enabled and in native resolution (it has 4:2:2 / 4:1:1 / 4:2:2 compensation as a feature).

Still the halo is not gone. However, and this is very important, earlier today I took some pictures with my Nikon D70s, which also shows a little bit of a halo, even with sharpening turned all the way down. I have no idea what they do internally, or if it’s even important to Nikon to be able to completely disable the edge enhancement, so I don’t know for sure if that’s a clean signal. Unfortunately, I don’t have it here right now, so I can’t upload.

But what this means is that it’s probably true that with Detail and V Detail at -7, the HVX is likely not doing anything to the signal, edge enhancement wise. Regarding the halo, it may be a function of CCDs as such, as the signal IS analog at some point, and there could possibly be some capacitance causing it at an analog level. I also still haven’t analyzed the analog component signal coming out of the camera, to see if it’s a codec issue (but if it is, I would consider that a real bug).

In any case, I’m finding that I’m able to compensate for it quite a lot with the echo cancellation technique I’ve described in another post in this thread. And with light wrap on body parts that are over bright backgrounds, it starts to look like a real composite.

Thanks,

Per

[Steve Wargo]

Where are you located? Maybe someone can work with you in person to get to the bottom of your issue. And the first thing that I would recommend is to follow Jan’s advice to the finest detail. You asked her to help and when she said to adjust your detail setting, you debated with her.

Steve Wargo
Tempe, Arizona
It’s a dry heat!

Sony HDCAM F-900 & HDW-2000/1 deck
5 Final Cut (not quite PRO) systems
Sony HVR-M25 HDV deck
Sony EX-1 on the way.

[Per Holmes]

Hi Steve,

I’m split between Los Angeles and Seattle.

But what a curious comment. I’ve done everything Jan suggests times a thousand. Before she asked. She suggested to change the detail settings. I told her that I’ve done meticulous and graphed analysis of over 60 combinations of the Detail and V Detail settings. I have done EVERY SINGLE COMBINATION. Jan’s answer was down the same alley as ‘are you sure you’ve plugged in the power?’.

But it appears you’ve not read the entire thread, which is still there for your perusal.

Best,

Per

[Per Holmes]

Hi Marcus,

I should only add, that the halo could also be caused by the pixel shifting process. As I understand it, the native CCDs in the HVX are actually not very high resolution, and the higher resolution is gained by interleaving these signals, which logically implies that some technical assumptions about being made about a certain chroma value the same way 4:2:2 makes assumptions about chroms that 4:4:4 does not (same chroma every two pixels). The pixel shifting process would necessarily do something similar to create 1280×1080 from 3 540×540 sensors (if that’s the exact number).

If that’s the case, then the halo is physically part of the camera design, and possibly most visible on a hefty change in color information such as going from a green screen to a person’s arm.

But if it’s physically part of the signal after the pixel shift, then I have no quarrel, because then that’s how Panasonic was able to deliver a camera with this resolution at this price. In that case, you get what you pay for, and that’s fine. I just want to make sure that we’re not dealing with some engineer not seeing the need for completely disabling an Unsharp Mask algorithm, which could eventually be fixed in software.

I’m going to do a little research on my Nikon D70s and find out if it does any pixel shifting, or resolution extrapolation. Probably not, as it is a 1 CCD camera, naturally, it’s a DSLR, but you never know. Otherwise, the Nikon is producing the halo as a function of a sharpness generator that is not completely off, but I don’t feel like starting to analyze a whole new camera.

But if the halo is inherent to the design, I have no beef. And it could well be. Raylight should then consider doing as an option what I did in Fusion, which does a quite good job at removing the halo by echoing the UV channels two pixels in the opposite direction and adding them back on top of they hold higher values.

Anyway, thanks for all your attention.

Cheers,

Per

[Jan Crittenden livingston]

[Per Holmes] “I should only add, that the halo could also be caused by the pixel shifting process. As I understand it, the native CCDs in the HVX are actually not very high resolution, and the higher resolution is gained by interleaving these signals, which logically implies that some technical assumptions about being made about a certain chroma value the same way 4:2:2 makes assumptions about chroms”

Hi Per,

Your explanation of the Pixel Shift says that you believe that there is a actual pixel to pixel match up somewhere, this is not true. What comes off of the CCD is an ANALOG signal, the offset is made to capture the areas of the green CCD which are non-photosensitive, the registers, and this is done with the red and blue CCDs. They are then clocked back into time and a snapshot is taken at 1080P. It is at this time the signal is changed into the digital domain. And BTW, this process is practiced by a good number of manufacturers in their Standard Def Cameras and have been doing so since 1990 or so and also in a couple of the small HD cameras but only on the Horizontal Domain.

As many have pointed out in this thread, Green screen with the HVX200 is a real breeze. There is something in your process, setup, lighting, or whatever that is causing your problem. I suggested that you back off your detail, and while you feel that might have been a “is the power on” sort of a remark, I note that Barry Green, who is one person that I feel probably knows the camera better than I do, also suggested the same along with another reference to a customer that does a lot of green screen work with the HVX200. And your reply to him is that there are lots of people all over the internet that are having a problem. Hmm, I have not found them. Would you post a couple of those threads?

In the meantime my offer to the fellow above with my frame grab is open to you as well, just send me an email with your email address in it and I will upload it to yousendit.com.

Best regards,

Jan

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

[Per Holmes]

Dear Jan,

Thanks for responding.

Well, it’s not very hard to find other people. Searching for ‘hvx green screen halo’ on Google, here are a couple of links. I’m just grabbing these without reading them again, so maybe one of them is something else.

https://dvinfo.net/conf/showthread.php?t=86997&page=2

https://www.dvxuser.com/V6/archive/index.php/t-88916.html

I communicated privately with the DV Info poster, who I think finally had talked himself into lighting being the cause (an even easier solution is to have everyone wear black, it matches the halo making it invisible), and had made what I consider a hefty (as a solution) 50 node Shake setup to remove this chroma echo thing. His setup included rotoscoping the halo, and my line of thinking then, why bother shooting on green screen at all, why not just roto the whole thing.

Regarding the Detail settings, I can say with certainty that the Detail -3 advice is not good advice. -3 simply has more edge sharpening than -7. If you read all these posts, I agree that -7 is actually OFF, at least on the Luma signal. The halo is still there in the chroma signal.

I have followed everyone’s large and small ideas to the utmost. There is no lighting solution that takes it away. There is no resolution and no setting that takes it away. Everyone who has uploaded footage that supposedly is without a halo CONTAINS a halo, or keying where the matte has been shrunk too much. In that case, I like my solution better, to reverse the chroma echo by 2 pixels as I described and then doing light wrap over bright areas. This actually produces a fully respectable key and retains practically all hair detail and semi-transparency.

I would absolutely LOVE to see a 1080p uncompressed still of a green screen that is without halo, and where the subject has a non-black edge, which would conceal the halo. Please send still to sales@hollywoodcamerawork.us.

I do still strongly believe the conclusions I have arrived at in this discussion, that this halo is a consequence of that pixel manipulation that is taking place to produce an image that is not a one-to-one pixel copy of what the CCD is seeing. All kinds of processing is taking place to do that, which is usually perceptually irrelevant.

And I’m not saying that this is wrong. You’re obviously providing amazing value for money with this camera, no doubt, and it’s OK to pull a few tricks to make it happen. If it is native to the way it designed, then I’m fine. I just don’t want it to be a bug, or something we’re all in denial about.

All I started out saying was that if this is simply caused by a detail generator not turned all the way down, even with the lowest settings, then I would spearhead a petition-drive to get a firmware that allows it to be completely disabled.

Best,

Per

[John Cummings]

“almost unusable for professional work ”

I may be wrong, but it seems to me that for professional work, using professional cameras and lenses might yield more professional results.

Or, it may indeed be that the flux capacitors are out of sync with the holographic emitters.

John

[Per Holmes]

What a bizarre response some people have to a perfectly legitimate inquiry.