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TOPIC: Keying out something that has green on foreground.

Keying out something that has green on foreground. 24 Jan 2019 20:23 #98655

  • Jonathan Levin
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Hi all.

I am trying to develop my skills with chroma key, and editing using Keyer effect in FCP X. I think I have the basics down pretty well: lighting background, more than basic understanding of the keyed effect and so on.

There is something that is hanging me up though. I have a shot where there is a greenish bottle that I am holding. The bottle is not stationary. Applying the keyed in FCP keys out my background very well, but it is also affecting the greenish bottle the I am holding. A few thoughts I had was to shoot against a BLUE screen(to late) or maybe create some sort of alpha channel and somehow mask the bottle. This may be called rotoscoping, not sure. Is there a way to make something that is affected by the keyed to reappear? I also thought about using some sort of image mask in FCP but that seems like it would work if the object is not moving.

Attached are a few frame grabs. I know what you must be thinking. But it's a little comedy thing I'm working on. Don't ask...

ScreenShot2019-01-24at2.18.42PM.jpg


ScreenShot2019-01-24at2.19.16PM.jpg


ScreenShot2019-01-24at2.19.36PM.jpg


ScreenShot2019-01-24at2.20.29PM.jpg
Last Edit: 24 Jan 2019 20:28 by Jonathan Levin. Reason: Missing screen shots
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Keying out something that has green on foreground. 25 Jan 2019 04:25 #98658

hmm …
a) your bg is not even lit, using the ColorMeter (Utilities), it tells it's wide variety of greens ;)

ScreenShot2019-01-25at05.10.29.jpg


… and the bottle contains green from that range of colors… so, no chance to adjust that

b) the keying changes the bottles overall appearance from green to beige …

c) if optional, re-shoot on blue
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Keying out something that has green on foreground. 25 Jan 2019 11:33 #98660

  • thinkfilm
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For producing good keys from difficult footage like yours FCPX might not be the best tool - although I find the built-in keyer produces great results in most cases. Personally, I use Hawaiki Keyer and I think it's superior to the built-in one. Even if you don't use Hawaiki Keyer, watching Simon Ubsell's tutorials on it and keying/compositing in general may be worth your time.

If you just want to use FCPX's native tools, I would first use the color tools to balance the green screen background and perhaps try to nudge some color separation with the bottle. As Karsten points out the background is unevenly lit and pre-keying color correction can help you here. Using the HSL color curves, you may need several instances of the effect to achieve the right balance and tonal separation. Likewise, you should also try and break-up the key by using two (or more) instances of the built-in keyer to manipulate different parts of the image. Ripple has a good tutorial on doing this and Hawaii in fact has a built-in secondary keyer in its plugin.

As they say, I hope this helps.
Last Edit: 25 Jan 2019 11:34 by thinkfilm.
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Keying out something that has green on foreground. 25 Jan 2019 13:03 #98661

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If this was shot on blue, even with uneven lighting, FCPX would have keyed is just fine.
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Keying out something that has green on foreground. 25 Jan 2019 17:29 #98668

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Thanks everyone.

I've been learning and testing out different situations using Keyer while waiting for some (any) work. As I was testing using myself as the talent, I started getting some really funny stuff. I've also been really honing my dual-system audio as well. I will share this when it's done. It's intentionally appalling!

Back to my issue, yes, shooting against blue would have saved the day. So would choosing something that wasn't green! So I may revisit this and use a Jack Daniels bottle instead. (Don't ask.)

I am very glad that this came up while just testing and not on an actual project, though I think I may have figured out an alternative, but later when I got deep in trouble :ohmy:

One thing that I've been doing is cropping as close as I can so less to key. Also shooting 4K Pro Res 422. When looking in Composite mode in the Keyer, If I see a bit of un even-ness, that is pretty well fixed using the Refine>Sample Color, carefully. And occasionally, Fill Holes.

The background is being lit by four Lowell Omnis, two on either side. The The Luma scope on my Atomos Ninja shows background at just about 50%, which is good from what I understand. My studio is quite small, but I try to keep subject (me) as far from BG as possible ~8 feet. I know the further the better. In really paying world setting, I think I would rent a studio that has a large green screen BG I could move further away.

I've read older threads on Keyer usage and that has helped to. I've looked into Hawaike Keyer too, but trying to do stuff on the cheap. For now.

I'm intrigued by using multiple instances of the Keyer.

The easiest fix for now appears to be reshoot on blue if subject is green like my Benefiber bottle, r use a different "prop". The Jack Daniels would be more fun anyway. :silly:

Last question: not know much about Rotoscoping, would this be something that would be useful for? And just how hard is it to Rotoscope. I know that major motion pictures must come up against this when they are keying and something in a scene has green that needs to remain in tact.

Thanks again!

JL
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Keying out something that has green on foreground. 26 Jan 2019 03:01 #98672

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You got a really good key on your talent. Duplicate the clip so that you have two clips, one over the other (you don't need the keyer on both - just the bottom clip). Use Draw Mask and mask around your product. Since its size and shape will not change dramatically over the life of the clip, you should be able to animate the Mask to follow the product relatively easily. The two clips together will look complete. You can keyframe Transforms and Control Points (if reshaping becomes necessary - perspective if it's turned, typically). The nice thing about Draw Mask is the amount of onscreen control you have over the masked area — you can click inside the area and drag the entire shape around making manual "tracking" pretty easy. Multiple point selections can drag portions of the shape, etc... It also doesn't matter if you "draw outside the lines" where your hands make contact with the product! Best advice is to make sure you have enough points to reform the shape as your hands move because you can't add points as part of an animation; but you don't have to reshape around the hands - just cut through them to keep the shape (if you get what I mean).

ScreenShot2019-01-25at8.41.23PM.jpg
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Keying out something that has green on foreground. 27 Jan 2019 20:36 #98681

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sc_fox

This was very helpful. Thanks so much. This is what I did:

1) Create copy of Keyed clip, place on top of Original Keyed clip in Project.

2) Delete Key effect from top clip. Add Draw mask effect to the top clip.

3) Draw (click) to make Mask based off of first frame in that clip.

Here is where I got confused. I was trying to add Key Frames for each move using the Key frame command in the Mask effect. To my surprise, you can add one key frame. After that the only option is to delete that Key Frame. It took me a little while to figure out that Key Frames are added AS YOU MOVE the mask. This was verified by looking at the "Show Video Animation" in timeline. I also found that I could keep adding key frames as needed if I found some places where the mask was not placed in the right place. I wish there was an on screen rotate for the mask. The Rotation tool and Degree setting in the Draw Mask effect are really clumsy to work with. Maybe there is a key command that allows for rotating a mask on screen. I love to know that one.

The only other thing I think I will try for my next test is to make the mask slightly smaller than the bottle.

You know what would be really amazing is if you could Make a Draw mask say on the first frame, and then somehow select all the Green key that is around that mask, and then just key that out without altering what is inside of that mask. Is this possible?
Last Edit: 27 Jan 2019 20:36 by Jonathan Levin.
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Keying out something that has green on foreground. 27 Jan 2019 22:36 #98683

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I am really sorry — I have taken a lot for granted.

When you draw a shape with Draw Mask you have two groups of keyframes you can manipulate: Transforms (includes Position, Rotation and Scale) and Control Points (which are the points you added to create your shape). You cannot keyframe an individual control point, you have to keyframe them all at once with a "main" keyframe setting.

Manipulating the shape:
First and foremost, you can simply click anywhere *inside* your shape and drag ALL Control Points at once together. Using a keyframe on the Transforms, you can keyframe the change in Position simply by dragging the shape from within its lines. Using Rotation will rotate ALL points and retain the shape and using Scale will reduce or expand the size of the shape and maintain the relative positions of all the drawn control points.

You can select one or more than one control point by Shift-dragging a selection rectangle to select multiple points OR you can simply Shift-Click on points to additively select multiple points, then drag one of the select points to move all the selected points together leaving the unselected points anchored to their current positions.

You can Click On any line segment between two points and move those two bounding points in unison.

Generally, once you set a keyframe on any parameter, you generally do not have to set another keyframe. Any time you move the playhead and move points, that automatically creates a new keyframe for that parameter on that playhead position. The exception to this rule is when you need to set a "hold" keyframe — for example, you need to pause an animation, you would move the playhead to the point at which the pause ends, *manually* set a keyframe, then move the playhead again and continue setting keyframes in a normal manner. That generally does not apply in this situation.

Another option you have is to keyframe only the Control Points — animate each point over time by dragging and repositioning them over time. This method is a major pain and occasionally necessary (for example, if you turn the product to show only the top creating a circle that you have to collapse ALL the points you use to fit the circle shape). Once you draw your original mask, you cannot add or subtract points in an animation! (You can use some creative cutting though.)

One more thing about bezier shapes - nowhere in any of the interfaces (FCPX/Motion) are the endpoints listed — only the control points (the actual points the lines pass through). That does not mean any movement you use to reshape the mask are NOT recorded. Everything you do is recorded, including "breaking" the line (creating a "hard angle") which you can do by selecting a point, holding down the Option key and dragging an endpoint. If you have a "hard" corner (no endpoints) you can create them by holding down the Command key and clicking and dragging away from a control point. If you want to "repair" a control point, click on any end point ("handle") control holding down the Control key and choose what type of point from the popup menu (choices are "Break Handle" or "Align Handle" — align handle is still "broken" but realigns with the "other side" of the control point.)

You just need enough of a mask to fill some holes and feather to "blend" the edges. Try not to over-complicate your life by making a too detailed mask (or one that's too "sharp" on the edges). Try to keep in mind what you're actually going to see when this is being played back at full speed.

With Draw Mask, if you need to use two masks, make another duplicate of the original clip and do not try to use two Draw Masks on the same clip. The only pixels in a clip with Draw Mask are those inside the mask. You cannot "add" to the mask, you can only take away more, unlike other effects where you can add multiple masks and add, subtract or *intersect* them to combine their effect together.

Too much?
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Keying out something that has green on foreground. 28 Jan 2019 21:31 #98700

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sc_fox,

Thanks again for a very detailed post! I've been getting some very good results using the advice and mercifully my clip is only a few seconds long, or this would take forever. But great stuff to know!

I also decided that for Keying, shooting at something like 4K at 60p instead of 30p would have helped somewhat to. When the green bottle raises up, I can clearly see "motion blur" on each frame until bottles is in a resting position. I think with 60p there would be some blurring but maybe not as bad. My Nikon/Atomos combination only allows me to go to 4K 30p.

Thank you for spending the time to add additional information.

Jonathan
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Keying out something that has green on foreground. 29 Jan 2019 01:37 #98705

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Consider increasing your shutter speed to reduce motion blur. If you go too high it will make the motion too jittery but used judiciously it can save you a bunch of time, with keying moving elements, and make the key in those areas much cleaner.
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