FS5: Green Screen Advice

[SamEdwards]

Denis Muren, who has more oscars than anyone else alive, says that Blue screen suppression is much less damaging to the FG image than green screen suppression.
So blue is often used in high end productions like Life of Pi, War of the Worlds, etc. Key edges are usually a bit easier to get with green screen. But high end productions will usually pay for the extra time it takes to pull a good matte from blue for the best possible result.
Many VFX shots have a lot of blue in the BG that is added (blue skies!), so a little blue spill is often preferable to green, which stands out like a sore thumb between an actor and a blue background.

 

[Harry Lime]

I've never keyed XAVC so I don't know how the edges hold up over say ProRes, compression artefacts are the main enemy not bit depth as they posterise the image data so in this case I would shoot 4K even if that meant going 8 bit on the FS5 as the output is to be HD the resolution will trump bit depth. The success of the key will be down to the compression and I don't know how well XAVC-L holds up if at all.

Definitely shoot REC709, if you're lighting the scene correctly there's not enough dynamic range to make shooting Log a sensible option especially in 8 bits.

Compression is always the enemy when you are keying. You will inevitably end up with an edge where the subject meets the process screen. This will be particularly noticeable where the contrast is the greatest (white shirt against blue/green screen). I stand by my recommendation to choose bit depth over resolution. Greater tonality will help with spill suppression and keying.

 

[Harry Lime]

As I recall from 'back in the day,' Blue was a pretty strong layer in the Kodak film stocks. (I think this was particularly true with 5295 - which as I recall was optimized for Blue Screen...)

We keyed 5248 / 5296 on Interview with the Vampire. Grain the size of golfballs.

 

[Nirv]

Compression is always the enemy when you are keying. You will inevitably end up with an edge where the subject meets the process screen. This will be particularly noticeable where the contrast is the greatest (white shirt against blue/green screen). I stand by my recommendation to choose bit depth over resolution. Greater tonality will help with spill suppression and keying.

You are entitled to be wrong.

 

[Harry Lime]

You are entitled to be wrong.

That's cute.

 

[broughtonfilm]

I think 4k is better because it's 100mb/s instead of 50mb/s. It's more data.

4K is 4x more pixels than HD, how is 100mb/s vs 50mb/s more data then? If anything, it's half the data.

 

[mitchino]

Errr - because a 10 sec clip recorded at 100mb/s contains 1GB of data, a 10 sec clip recorded at 50mb/s contains 500mb of data.

 

[mitchino]

So just did a test filming a fluffy teddy bear, 4K out of the FS5 hdmi, using a 300MB/s SD card in my Video Assist 4K, shutter speed 1/100, dropped the clip into an HD timeline in FCPX and got a lovely result with a one click key. Very pleased! It'll definitely exceed the clients expectations anyway. Have to say shooting ProRes HQ and not dealing with that horrible Sony file structure is bloody marvellous.

 

[broughtonfilm]

Errr - because a 10 sec clip recorded at 100mb/s contains 1GB of data, a 10 sec clip recorded at 50mb/s contains 500mb of data.

Bravo!

 

[Nirv]

Errr - because a 10 sec clip recorded at 100mb/s contains 1GB of data, a 10 sec clip recorded at 50mb/s contains 500mb of data.

This post should be pinned as a textbook example of not knowing the difference between milli (m), Mega (M), bits (b) and Bytes (B).

10 secs of 100Mb/s does not give you 1 GB of data!

 

[broughtonfilm]

This post should be pinned as a textbook example of not knowing the difference between milli (m), Mega (M), bits (b) and Bytes (B).

10 secs of 100Mb/s does not give you 1 GB of data!

That too but it was not even my point. The confusion is about what "data" really matters. Not "data" as size of files on the disk but "data" as information about color and luminance of each pixel. If 4K is 4x more the number of pixels than HD but is only 100mb/s (vs 50mb/s in HD) that means it has only half the information (data) about each pixel compared to HD, meaning it is more compressed.

 

[mitchino]

That too but it was not even my point. The confusion is about what "data" really matters. Not "data" as size of files on the disk but "data" as information about color and luminance of each pixel. If 4K is 4x more the number of pixels than HD but is only 100mb/s (vs 50mb/s in HD) that means it has only half the information (data) about each pixel compared to HD, meaning it is more compressed.

I 100% agree that 100mb/s 4K contains less data than 50mb/s HD, however your earlier post was a bit confusing, you said "4K is 4x more pixels than HD, how is 100mb/s vs 50mb/s more data then? If anything, it's half the data."

I assumed you were comparing 100mb/s 4K to 50mb/s 4K.

 

[broughtonfilm]

I 100% agree that 100mb/s 4K contains less data than 50mb/s HD, however your earlier post was a bit confusing, you said "4K is 4x more pixels than HD, how is 100mb/s vs 50mb/s more data then? If anything, it's half the data."

I assumed you were comparing 100mb/s 4K to 50mb/s 4K.

What you say makes no sense, as my comment was referring to a specific sentence from SamEd's comment (which I quoted above my original comment).

Anyway, I'm glad that recording with external recorder worked for you.