First Greenscreen shoot, FS5

[Mike Watson]

I don't do a lot of greenscreen work, maybe once or twice a year.

I have a big shoot next Weds and Thurs that the FS5 would be perfect for. Inside a vehicle, so the small size would be a big help.

I'm shooting my corporate stuff in XAVC.

What should I shoot the greenscreen stuff in?

Would you shoot in HD or UHD? The deliverable is HD.

[Jody Arnott]

I don't know much about green screen work, but just for the fact that in UHD you'd be able to crop in and create different shot sizes, that would be my choice.

[Peter Newsom]

Originally Posted by Mike Watson

I don't do a lot of greenscreen work, maybe once or twice a year.

I have a big shoot next Weds and Thurs that the FS5 would be perfect for. Inside a vehicle, so the small size would be a big help.

I'm shooting my corporate stuff in XAVC.

What should I shoot the greenscreen stuff in?

Would you shoot in HD or UHD? The deliverable is HD.

I would think that 10 bit 422 HD would be the better choice.

[Dave Sperling]

My first instinct would be to shoot in UHD to have the higher pixel count for cleaner edges -- as long as you're doing the compositing in UHD.

I'm assuming that when you say the deliverable is in HD that you mean the final composite?

But my first recommendation is to do a test including your finishing pipeline.

[Jody Arnott]

Originally Posted by Peter Newsom

I would think that 10 bit 422 HD would be the better choice.

If you're shooting in UHD and delivering in 1920x1080, doesn't the image essentially become 10 bit 422?

[Peter Newsom]

Pretty sure that the original 8 bit 420 recording represents all the data you have. Putting it in a bigger bag(10bit 422) won't add any thing that wasn't there in the first place.

[Chris Medico]

Originally Posted by Mike Watson

I don't do a lot of greenscreen work, maybe once or twice a year.

I have a big shoot next Weds and Thurs that the FS5 would be perfect for. Inside a vehicle, so the small size would be a big help.

I'm shooting my corporate stuff in XAVC.

What should I shoot the greenscreen stuff in?

Would you shoot in HD or UHD? The deliverable is HD.

My opinion is the biggest thing you need to be careful with is your DOF. If you are shooting in a small space that suggests that the subject will be close to the camera. That will be OK with a wide lens where the DOF is usually pretty deep but if you need a tighter shot with say a 35mm the DOF on the short end of the focus scale can be quite shallow. Soft edges can be a real problem to key. I highly recommend doing a test with the camera setup at similar distances/lenses/iris to the subject and make sure you can key the image.

You can take that opportunity to shoot it in 1080 and UHD and see if that makes a difference. Keyers have gotten pretty good at keying 4:2:0 though it wouldn't be my first choice. I personally would lean towards 1080.

[Dave Sperling]

There are really quite a few issues in your basic question, and my feeling is that a test of some sort would really be called for to get the best key.
In terms of UHD vs 1080, you have the 4:2:0 vs 4:2:2 issue -- Traditionally I would always go with 422 because it gives me better COLOR RESOLUTION -- but that is predicated on both being at the same pixel recording resolution. Without knowing exactly how the 420 compression is working on the green channel, combined with the way the colors of your actual foreground people/objects are compressed, it's hard to get a sense of whether there is any real improvement in the UHD compared with the 1080. My guess is that the UHD will generally produce a cleaner matte.
In terms of 8-bit vs 10-bit, unless you're doing serious color CORRECTION I would guess that this wouldn't be much of a contributing factor. However -- I'm basing that on having your recording in REC709. I personally always try to do my Green Screen and Blue Screen shoots recording in normal color space (rather than s-log) because I'd rather not require the post process software to adjust color before creating the matte. Most of my color matte shoots are in controlled lighting conditions where I don't need s-log. If you need to shoot s-log for increased dynamic range in the foreground, then my feeling would be to go with the 10-bit 1080.
Anti-aliasing -- something we tend to forget about -- but this is something else that messes with your matte. Normally UHD cameras recording in UHD will have optimized anti-aliasing for that resolution, so another vote for UHD.

Chris brings up a great point about soft edges and DOF. I also want to mention some other issues:

Reflections -- In a tight space with a lot of curved and potentially reflective surfaces you need to try to limit the reflections of the green backdrop in the car! If most of the reflections are in one direction a pola filter can sometimes be helpful, but it is not a panacea (and you lose about 1 1/2 stops of light). Make sure to 'wrap' your subjects with soft back/edge light -- and adding 1/4 minus green to these lights can really help!

Subject movement -- I often will shoot matte shots with a slightly faster shutter speed. It helps make edges sharper when there is movement. (I've found this particularly useful with ballet style dancers and athletes doing extreme movements). Many compositing systems can create a motion blur AFTER the clean matte has been pulled!

Exposure -- Lest we forget, you want to have good exposure for what you're shooting. This does NOT mean cranking up the gain in the camera! I still use an F3 for most of my 1080 matte work - it's sensor and electronics are incredibly noise-free, and it can output 4:4:4. You want a clean, noise-free signal -- don't push your gain/ISO!

Compositing systems are not all the same! -- If you do a test, finish it using the same system that will be used for the final output!

Look at your test results on a BIG monitor -- remember, when testing green screen 'pixel-peeping' is a good thing!

And... Having scared you with all of the above, let's just say that you'll be surprised how well the eventual mattes can work!

[Mike Watson]

Shot today. XAVC 50Mbit.

This is a rather quick edit, but for a first pass I thought it turned out ok.

Green Screen Sample on Vimeo