GH4 Interested in how the GH4 handles "green screen" in 4k & HD...

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david_p

Veteran
would love to hear from some new GH4 owners opinions on its green screen capabilities especially 4k internal downsized to 1080.

thanks!
david
 
Assuming you mean recording in camera, 4:2:0 generally will not hold together very well for green screen and compositing when compared to a 4:2:2 camera/recorder, but if you know how to light, you can get an acceptable result. I shot a series of PSAs on the FS700 internal recorder on a green screen stage last month and they keys were not great but they were usable for a budget challenged client. I too am curious if the 200Mbps high data rate might help with green screen and what 4k would be capable of.
 
right now for GS i either use an EX1 (420) or a C100 also (420). not the best obviously. was wondering it anything might be gained by 4k internal (even though its only 4:2:0) downsampling or scaling down to get a bit of a bump in performance coming from 4k. of course i can get an Atomos star or ninja but was hoping i could squeeze a bit more out of the gh4 native internal than my other cameras I've been using.

thanks!
david
 
The GH4 has done well in my green screen tests. Just like using our old Red One & Epic, we can shoot a waist up shot placed in a 1080 timeline at 50% zoom, and then reframe to a 100% zoom for a tight shot. For what it's worth, we have not had issues keying 4:2:0 footage for a very long time.
 
4k down converted to 1080p in post will give you close to 4:4:4 color sampling compared to shooting 1080p native which of course would be 4:2:0. With that said 4:4:4 vs 4:2:0 is not a night and day difference as long as the shot is good. This myth of 4:2:0 has been exaggerated for way too long. Yeah your edges may be a bit more accurate with 4:4:4 but the overall shot isn't magically going to key better or easier with 4:4:4. All 4:4:4 will do is help make the edges not as jagged and help with very fine details like hair. In fact I wouldn't even call a 4:2:0 more jagged, just a bit lower resolution edges is some cases. If you use software that up samples the chroma like 5D2RGB or Adobe After Effects you get a re sampled 4:4:4 from a 4:2:0 source anyway. Yeah it doesn't have the fine edge detail but it eliminates the pixelated edges you can sometimes see with 4:2:0. The single bayer sensor process in the camera is butchering the original color way more then the 4:2:0 sampling. Only true way to have a natural 4:4:4 is to have a 3 chip camera that records 4:4:4. Or start with 4k and down convert to HD which can have close to the same effect.

It is the lighting and detail you are keying that will determine how well you can key a shot. keyers don't like to have their ranges pushed too hard or they start to look fake. Instead of cranking the settings in the keyere the better way to key is to use multiple keyers for different segments of the shot and comp those pieces together. This is how you make sure the edges look the same across all the different lighting levels. 4:4:4 does not change this in any way. A shot with lighting all over the place will still have to push a keyer way too hard.
 
By the way people think I'm nuts for saying this but taking 1080p footage and down converting to 960x540 can show you the exact same effect. So if you want to see for yourself if it works try it with some existing 1080p GS footage you have. Make sure you do it in a decent program like After Effects. If you are keying right in the NLE thats the first part of your problem.
 
David W. Jones said:
We have not had issues getting a good key in our NLE for a very long time now.
Click to expand...

Don't get me wrong they have come a long way but they will never be a match for keying in a true compositing application. Dropping a single keying filter onto a clip can only get you so far. They are capable of some amazing results now but I can still pull a better key in a compositing applications. We are talking very subtle results here but for serious FX work it can make a difference. A compositor typically has to work with less then flattering material and has to learn how to really massage the entire picture to keep every edge as natural looking as possible. I'm talking more full body action shot type scenes and not talking head situations.
 
Agree absolutely.

But most of my work are quick turn TV commercials where we just don't have the needed time with the client sitting behind you going, are we there yet?
 
I shot a project a couple of years ago and used the DV Matte Pro plug in in FCP 7.1. The footage was shot on a Panasonic HPX3100 so it was 4:2:2. I found that I could pull a surprisingly good key with the DV Matte Pro plug in but when the actors waved their hands quickly or gestured with their arms, there was green bleeding through the interpolated motion in the frames that I couldn't eliminate with the DV Matte Pro keyer. Gave it to a friend, she used AE's Keylight and with some tweakinbg, eliminated any of the green bleed so I totally agree that different keyers work well for different apps or parts of a composite. If I only had and knew how to use AE. I refuse to pay a monthly license to Adobe for the privilege of using the current version of AE, what would be the last version before they went to the cloud licensing I could buy and learn the app?

The more I read about the GH4, the more it is seeming like a smart plan to shoot almost everything in 4k and just edit it on a 1080 timeline. Besides this keying issue, all of the reports I am seeing say that shooting in 4k and editing in 1080 looks noticeably sharper and better. I have a new GH4 sitting in a box here, have not even had time to open it yet. much less try it out, too many work deadlines. One more question, can FCP 7.1 support 4K from the GH4 or do I have to finally upgrade to FCPX? I plan on doing so, but have been holding off since I have some long term television projects that are mid-project and were started in FCP 7.1.
 
puredrifting said:
I shot a project a couple of years ago and used the DV Matte Pro plug in in FCP 7.1. The footage was shot on a Panasonic HPX3100 so it was 4:2:2. I found that I could pull a surprisingly good key with the DV Matte Pro plug in but when the actors waved their hands quickly or gestured with their arms, there was green bleeding through the interpolated motion in the frames that I couldn't eliminate with the DV Matte Pro keyer. Gave it to a friend, she used AE's Keylight and with some tweakinbg, eliminated any of the green bleed so I totally agree that different keyers work well for different apps or parts of a composite. If I only had and knew how to use AE. I refuse to pay a monthly license to Adobe for the privilege of using the current version of AE, what would be the last version before they went to the cloud licensing I could buy and learn the app?

The more I read about the GH4, the more it is seeming like a smart plan to shoot almost everything in 4k and just edit it on a 1080 timeline. Besides this keying issue, all of the reports I am seeing say that shooting in 4k and editing in 1080 looks noticeably sharper and better. I have a new GH4 sitting in a box here, have not even had time to open it yet. much less try it out, too many work deadlines. One more question, can FCP 7.1 support 4K from the GH4 or do I have to finally upgrade to FCPX? I plan on doing so, but have been holding off since I have some long term television projects that are mid-project and were started in FCP 7.1.
Click to expand...

With FCP7 you typically have to convert all material to ProRes on import. I am pretty sure doing so will work fine with 4k material although I no longer have FCP7 to try it out. I remember once working on some RED 4k material we shot in FC7. I cannot recall if this was still 4k or if the shots were down converted to 1080p first. Sorry it has been a few years since I did that. You could use Compressor to convert to ProRes 1080p first before you edit. This way you will just be editing some darn good looking 1080p material which you already know you can slice through like butter.
 
Most Scientiffick Test 3V3R! Hacked GH4 5K RAW

Most Scientiffick Test 3V3R! Hacked GH4 5K RAW

Most Scientiffick Test 3V3R! Hacked GH4 5K RAW ALL settings at +/- infinity.
Please calibrate your monitors accordingly. Test conducted in a green shoebox.
Hundreds of crew and technicians spent days conceptualizing, pre-lighting, shooting
and editing.

Conclusion: it handles fine.

Due to the limited bandwidth and time space gravity issues this file is not downloadable...
Sorry.


PS - footage edited on iTARDIS Pro OSZ
 
With just a fairly properly lit green screen, the GH2 and Adobe Premiere's built in Ultra plug-in I could pull near perfect keys. My first try with 4K on the GH4 was a breeze to get a beautiful key. Granted, this is talking news report style, not action scene compositing, but I would be shocked if you couldn't get a great key with a decent setup in any situation. Yes, yes, I know 4:2:2 footage is definitely better. 4:2:2 Pro-Res from the Black Magic Camera I used for a while was a bit easier to key, a bit more forgiving, but if you take any time setting up and know a bit about what you're doing, I'm confident that you'll be able to do a near perfect key with any footage from the GH4.
 
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