HV20 working out well for greenscreen!

[Ben Syverson]

Thanks for the link! Interesting... The HDMI definitely has more resolution. Though I think I would take the hit in resolution when recording in the field... It's worth it to not be tethered.

However, it's a different story in the greenscreen studio. If you have a computer capable of taking the Intensity card and you do lots of greenscreen, it's easily worth the $250.

I am impressed with how well the HDV holds up, though. Brightly colored details do better with HDMI, but that's to be expected. For most greenscreen subjects, the biggest hit you'll take by using HDV over HDMI is the loss of a little resolution. The 4:2:0 vs 4:2:2 is not a big deal, and your edges should look similar.

BTW, this is with about 5 minutes of fiddling with dvmatte -- the results could be improved by spending a little more time with it. Also, having a shot of just the greenscreen without the subject would let me do a screen correction pass, which would make this shot look about a million times better. And I didn't bother trying to protect the almost-green ironing board, which would be keyable if the greenscreen wasn't so dark and blue...

[Anton Galimzyanov]

Ben, great results!!!

Well, I still think an uncompressed version looks better (edges are cleaner, without 4.2.0 "jadges"). A main problem, at least for me, is pulling a good key out from hairs "on a wind". In my opinion, that kind of problem lies not in compression algorithms, but rather in not-so-perfect camera resolution (compared to F950, Viper or film negatives). What do you think, Ben - is it possible to create a good matte from medium and long shots of subgects with thin hairs?

And yes, I use HV20+Intensity for all exterior shots (a pair of 5kW generators, lots of lights, cables, monitors etc.. he-he, computer is such a small thing among all that stuff.. -))) Anyway, I'm wating for this amazing device from Cineform team: http://www.cineform.com/products/CineFormRecorder.htm

[Les Caudle]

Ben - did Anton's images give you what you need for HDV to HDMI comparison?

I'm mucking around with light levels and want to have it all set up correctly before I post anything.

Trying to find the most optimum level for the HV20 (someone said 2000 lux was best level for HV20, but I need to confirm this somewhere).

And, the best level for green screen (I've got 2 dedicated fluorescents for the screen, 3 for the 'talent'.

All my light metering with a Sekonic has been for strobes, so I'm having to learn how to use it for video.

BTW - do we have to wait for MacWorld to try a demo version of the new dvMatt Pro?

[Les Caudle]

Anton - do you have any tips for setting up the HV20 for best results thru HDMI?

What light level gives optimum results with the HV20's image sensor and lens?

[Ben Syverson]

Originally Posted by Anton Galimzyanov

What do you think, Ben - is it possible to create a good matte from medium and long shots of subgects with thin hairs?

Definitely! Of course, if you can zoom in or move the camera closer, it's always better, since you're utilizing more of the sensor. You can then shrink the subject to fit the frame. Of course, this doesn't help you if you need to have a figure walk from one side of the frame to another or something like that...

But whatever detail is captured in the shot can be reproduced. Getting a screen correction plate (just the greenscreen, no subject) is very important. Without it, you have to choose between detailed edges and uneven lighting on your screen corrupting the background...

BTW, the 4:2:0 "jaggies" are my fault -- I didn't sufficiently smooth the chroma channels in that shot...

Originally Posted by Les Caudle

Ben - did Anton's images give you what you need for HDV to HDMI comparison?

Yeah, as I briefly mentioned, the HDMI shows an improvement, but it's not a quantum leap. Definitely worth doing if you have the resources (mostly for the small resolution boost), but it shouldn't keep you from shooting tape when you need to.

As for lighting: forget about Lux... And footcandles... And any objective measure of light for that matter. What you really want to pay attention to is the subjective reading of the HV20 -- use the photo button trick to get to the f-stop you want, and a shutter speed of 1/48th (assuming 24p). It's fine to shoot wide open, for example f/1.8 @ 1/48. If you can't get there, add light.

Hopefully you can monitor your set live, using scopes. The most critical thing is to get the lighting even, so pay attention to your RGB parade. You want the screen to be at 70% RGB (about 180/255, or somewhere around 70 IRE). That will give your screen some "headroom" to reproduce highlights.

I have some Rosco Chroma Green gels on order -- they clip everything but a big spike in the green frequencies of light. I'm eager to test them as greenscreen lights... They should give a much greener screen, regardless of the material...

Good luck!

[Anton Galimzyanov]

Getting a screen correction plate (just the greenscreen, no subject) is very important. Without it, you have to choose between detailed edges and uneven lighting on your screen corrupting the background...

What a beautiful idea! I've never tried it before (stupid me).
As far as I understand I should create a matte from greenscreen room, and then apply it as a 'background' to my key comp.
I'll definitely try it next time. I cherish a hope those ugly semi-transparent blinking hairs of models will be clearly visible. Thanks, Ben!

Les,
HV-20 is very hungry for light, I hate HV20's noise in shadow areas.
But don't overdo with lighting. You could use something like Adobe OnLocation to control an amount of light in realtime.
For greenscreen work, my background is lit 2 stops less than a foreground object (bg: 65-70% RGB)

[Ben Syverson]

Originally Posted by Anton Galimzyanov

What a beautiful idea! I've never tried it before (stupid me).
As far as I understand I should create a matte from greenscreen room, and then apply it as a 'background' to my key comp.

Sort of -- your keying software needs to be able to incorporate the "clean plate" in its process. In dvmatte, it's a separate plugin. You apply the screen correction plugin (Screenfix) to your greenscreen footage, and then feed it a still (or movie) of just the screen, with no subject. Then you choose the color of the screen you want to equalize to. Screenfix then nukes your entire screen to that color, while retaining all edge detail.

You then have a totally even shot, and can pass this right into dvmatte. The results can be insanely good!

Originally Posted by Anton Galimzyanov

For greenscreen work, my background is lit 2 stops less than a foreground object (bg: 65-70% RGB)

In my last post I mentioned wanting to be at 70% RGB -- I should have been more specific. What you really want is to be at:
R: 0% G: 70% B: 0%

In fact, 80% may be a better target unless you have tons of highlight detail (read: blonde hair) to deal with.

The shot that I used to compare HDV and HDMI had a widely ranging background, with a midpoint somewhere around:
R: 24% G: 65% B: 38%

...which means that there's only an average of around 34% difference between the green channel and the R&B channels. The more we can increase this distance, the better, because more difference translates directly to more subtle edges and lower the noise in our matte.

This is where I think the Rosco Chroma Green gels will be really helpful, by knocking down the R&B output of your screen lights so that your screen has no choice but to bounce green light back to you. You'll never get to 0% in R&B, but you should feel proud if you can get to:
R: 10% G: 70-80% B: 10%

If you can get that level pretty evenly across your screen, you should be able to make a simply incredible composite.

[Les Caudle]

Ben - please post your findings when your green filters arrive.

I had thought of green filters also, but got negative feedback on the FCP forum (saying only needed if background is white) and would end up with more green spill.

But, it sure sounds like a great idea to me.

As to the "clean plate" - this is part of the workflow of dvMatte Pro?

I was hoping a watermarked version of the new release would get posted, so that I could try it out. Never hurts to have more feedback before going 'live' with a new release.

[Ben Syverson]

Originally Posted by Les Caudle

I had thought of green filters also, but got negative feedback on the FCP forum (saying only needed if background is white) and would end up with more green spill.

If there's more green spill, it will only be because the screen is greener! The greenscreen lights should always be flagged off and kept from directly hitting the back of your subject. It's also good to keep some distance between your subject and the screen, and be conscious of reflections... If your subject is holding a shiny metallic object and it reflects a pure green from the screen, you'll be stuck making a traveling matte for that area....

Originally Posted by Les Caudle

As to the "clean plate" - this is part of the workflow of dvMatte Pro?

It's part of the ideal workflow. I know that most people won't do it, but those that do will come away with incomparably better composites.

Originally Posted by Les Caudle

I was hoping a watermarked version of the new release would get posted, so that I could try it out. Never hurts to have more feedback before going 'live' with a new release.

Unfortunately, the beta cycle is over, but I will let you know the second we release the demo! :)

[Ben Syverson]

BTW, I posted the results of my gel testing on the following thread:
http://dvinfo.net/conf/showthread.php?p=784330

Bottom line: gels rule! I'll never again shoot greenscreen without them!

[Les Caudle]

Ben - here's a single frame recorded with HV20 thru HDMI live 24p to ProRes 422 HQ (reverse telecined using compressor as outlined in http://docs.info.apple.com/article.html?artnum=306389).

I'm the subject, and am curious how the blond hair can be masked from the green screen with your new tool. I understand blond and green is tough.

http://www.downloadfundraiser.com/m/singleFrame24p.mov

Thanks!

[Ben Syverson]

Les, blonde hair is extreeemely tough -- the whole new version was basically created to solve that one problem!

Here's what I could get from your shot. This would be assuming that you had a good screen correction plate. I hacked one together in Photoshop.

The result is not bad at all to my eyes! But it would be greatly improved by a brighter screen...

[Les Caudle]

Ben - that looks great!

But, are you saying the green screen was not bright enough and you had to work on it in photoshop?

I was hoping to see what the results would look like using just the new dvMatte Pro.

If it would be useful, I could iron the green screen, turn up the lights (got to re-read this thread on setting the proper levels) and post a small clip with some motion in it.

BTW - I also did a Photoshop export of that frame from FCP. When I opened it in Photoshop (on a Windows XP box), it did not have an embedded profile.

Is there a way to assign one within FCP?

If not, what profile should I assign, maybe Apple RGB?

I'm also going to have to get my head around how to deal with the shift from Apple's gamma to the more universal gamma found on the PC.

[Ben Syverson]

No, I'm just saying I had to hack together a fake screen correction image. It's just an empty shot of the greenscreen with no subject, but everything else set the same as the main shot. With software, you can correct the background to be more even if you have a screen correction shot. I've attached the image that I cooked up.

I took that and the image you posted and ran it through dvmatte pro, so what you're seeing is direct output from FCP.

BTW, you probably don't want a color profile associated with your stills. HD is essentially sRGB, and so is your XP box, so even without a profile in PS, you should be seeing accurate colors. Profiles tend to confuse people anyway, so I only recommend you use them when you're dealing with images that have very wide or different colorspaces such as Adobe RGB.

If you have a PC, don't sweat the difference between Apple gamma (1.8) and PC gamma (2.2). FCP handles the gamma conversion behind the scenes. If you want to be extra faithful, you can apply the sRGB profile to frame grabs from FCP in PS, when you're on your Mac. That way PS will know to darken the frame up a bit for viewing. Again, not needed on a PC.

Make sense? Or just more confusing? :)

[Les Caudle]

Ben - ah, I understand. So as long as the camera is stationary (probably a good assumption for non-star wars filming - the screen correction image can help to get a better mask.

As to color profiles, I'm used to working with RAW still images and doing the editing in Adobe RGB with a convertion to sRGB to output for the web.

I don't have Photoshop installed in the Mac, I suppose I will.

But, you seem to be saying that I can assign a profile of sRGB (on the PC) if I open a grab created from FCP on the Mac.

As for the gamma, if I open the sRGB labeled PS file on the PC, you seem to say that I don't have to worry about gamma?

I'm going to have to deal with similar issues (on gamma) when outputting Flash using Squeeze. I'll probably do that on the Mac as it Squeeze will eat ProRes 422 HQ on the Mac, but doesn't know what to do with it on the PC.

BTW - saw that Sorensen just added H.264 to Squeeze. Have to see if any advantages over Compressor.

Cheers!