Re: Disappointing image quality, especially for chroma keying
 

My tip is to use minus-green (magenta) on the backlight/rim lights. It cancels out green spill.

Re: Disappointing image quality, especially for chroma keying
 

and my tip is use a waveform monitor to check your evenness of lighting. If your lighting is reasonably even, your WFM will have a straight line across it.

Re: Disappointing image quality, especially for chroma keying
 

Gee I looked through this whole thread before going back at looking at the stills.
Yes garbage in garbage out. Something is wrong with your lens and Alistair is probably right its likely back focus is way out on the speed booster. A lot of people don't understand how to set back focus with a zoom lens. It needs to be right on the money.
Plus - what are you using as a green screen material? Doesn't look like proper material to me at all. No saturation and too wrinkled.

Please don't blame the camera for this

Re: Disappointing image quality, especially for chroma keying
 

Chromakey can be tough . . . the background lighting is usually the culprit; of course, the use of proc amps, filters a tong of 'tweening on the post side; I see hot spots on the background lighting, and certainly uneven levels - which is tough to get a clean key from.

I use to use muslin green backgrounds; before that, I painted cycs with blue screen paint (not cheap!) I use LED chroma key rings and backgrounds now, and always get easy, clean keys!! (Chroma key light ring and retro-reflective backgrounds. Green screen.)

You may want to consider retro reflective backgrounds and led technology - here are some suppliers . . .
DATAVIDEO LD-1 CHROMAKEY RING | Datavideo

Reflecmedia: Changing the art of chroma key

and a really cool led light ring for TELEPROMPTERS at Chroma key light ring and retro-reflective backgrounds. Green screen.

Re: Disappointing image quality, especially for chroma keying
 

I was just looking around for some examples of green screen footage I've shot with the FS700 and remembered that I shot all the green screen for Chris Landreth's "Subconscious Password" with two FS700s in CineGamma 4. I was the DP and stereographer. It was recently shortlisted for an Academy Award nomination.
We shot most of it at 4 and 8 frames per second and recorded direct to ProRes422HQ (and AVCHD for backup.)

Re: Disappointing image quality, especially for chroma keying
 

Bit late to this but i've done keying with the 700.

My observations:

You need to record 4:2:2 out of the camera, a shuttle costs next to nothing and you'd be insane to not do this.

You only care about edges, most of the green screen would be garbaged out, so focus on those areas.

Be very very careful with lenses and apertures. In the spirit of garbage in and out, poor lenses can add aberrations that are way harder than colour sampling to remove. Also be very mindful of diffraction at wider stops. Diffraction (this is what i'm calling it) can made the RGB parts of the light wrap differently around the edges - so the blue channel edge will be different to R and G, it's very obvious when wide open and lead into some pretty hairy keying.

Keying is an art form, there's no such thing as a single button keyer unless you are super careful with how you shoot and what you are looking for at the end. I work in Nuke with all manner of different keying approaches for different shots, different subjects and conditions. There is no one keyer to rule them all and invariably keying means using combinations of approaches.

hth
Paul

Re: Disappointing image quality, especially for chroma keying
 

Paul, I may be wrong but I think diffraction is something that happens at very closed f stops due to light bending around the small opening. Sounds like what you are talking about is basic chromatic aberration which is highest at wide open stops and will vary with the quality of the lens.
Its just nomenclature though. You're point is well taken.

Re: Disappointing image quality, especially for chroma keying
 

You're right. I'm calling it diffraction because it's what the light does - it's diffracting around the edges of the subject (not lens). Each wavelength is being spread out differently. So i'm probably going to confuse people who think of diffraction as something that happens with a lens closed down but i think i'm using the scientific version of the word (perhaps incorrectly!)

I guess it's similar to the effect of waving your hand in front of a lens when it is wide open and focus is in the distance, you'll see the background image distort as the light bends around your fingers. Cool effect, but not for post people...

It's one of those things that i see rarely mentioned but for some shots and some lenses it's really quite apparent and a real pain. I've seen samples of Epic footage that shows the same problem, so it's physics based not sensor.

cheers
Paul