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Blue Screen HD

Published : 5th July 2004


Just when I need them, I cant seem to find my notes...does anybody have specific f900 set up numbers for blue screen work?

Thanks,

Howard Wexler



Other than detail, what settings would need to be different for blue screen than for regular ol' shooting?

Did I misunderstand the question?

Randy Miler, DP in LA



My impression is that it's better to light the bluescreen correctly, getting as pure and even blue as possible, and avoid doing anything in the HD camera to further tweak the color with the Matrix, which should be Off (as well as Detail).

Again, just as with Detail, pushing chroma with the Matrix in any direction tends to add artificial edges around objects (you can see this on a big HD monitor as you pump up chroma in a DaVinci session.)

Don't know about Gamma and Black Gamma settings, but I assume that the goal here is to minimize noise, which you can get if you try and go for too low of a contrast by pushing the Gamma settings too far.

David Mullen ASC
Cinematographer / L.A.



A few opinions -

You want your subject to have the same look as he does on the rest of your sets or locations. Detail is probably the only variable you would want to consider altering, but usually it is already turned lower than the factory setting so you might only lower it further if you have done a test and the compositor is having trouble with the edges.

Although detail can be added in post, the most subtle and best controls are in the camera. For under $500K budget features film out is not a given, and HD shot without any detail looks too soft on most displays whether CRT, LCD, Plasma, DLP or DILA projectors.

Shooting with detail on but the level set down to -35 to -70 is an area of good compromise. With detail on you can use skin detail softening, with it off everything is soft.

These notes 1. and 2. from Sean Fairburn bear repeating :

re: new F900/3 software

1. I run detail ON and set low to -69 master. On and low is better for me than OFF.

2. The Frequency and the Black Limiter controls have been switched from before. The best smallest edge was at +99 to best and smallest edge now at -99.

So for F900/3 Limiter settings of 38 38 99 (make those negatives for the /2 and older software) may give you the thinner edge you are looking for but still give you an edge for a compositor to work with.

If possible choose your compositor before the blue screen shooting days begin. The first day you can take a tape from the studio, race across town to a post facility, and in an hour capture the good takes on a non-linear HD system and copy the HD data to a Firewire drive. Then test individual frames on any Mac or PC with After Effects, Combustion, Shake or other software. Primatte and Ultimatte plug ins are popular.

If you can afford a second hour on the non-linear HD system your artist could do his tests with full motion while the HD captured footage is on the array and you get to see the composite on a HD video monitor not just on the desktop.

Other notes :

Usually you want your screen exposure to be less than you key, unless you are keying into a darker scene.

A waveform monitor helps check how even the lighting is on the screen, but zebras work too.

Sufficient distance from subject to bluescreen helps minimize spill onto the subject.

Rehearse your blocking, moving actors need the most even background, static shots allow "garbage mattes" to be quickly created.

Some DP´s use amber or straw gel on the back lights for bluescreen, soft pink or magenta for backlights on greenscreen.

If you get the hair right the rest will follow, watch carefully for hot spots on the top of the heads, especially bald ones.

Avoid chrome, but glass (but not eyeglasses!) and smoke, while difficult to key add a great deal to the realism of the effect.

Including a few props with the talent can help the realism as well.

Jeff Blauvelt
HD Cinema
NY/NE (Westport, CT)
LA/West (Pacific Palisades, CA)



Actually let me check with some DIT gurus about the Detail Limiter settings

The negatives and positives switch in the software still has me confused

Jeff Blauvelt
HD Cinema



>You want your subject to have the same look as he does on the rest of >your sets or locations.

Of course if your shooting with diffusion you should remove it for green screen work, this might sound obvious to everyone but I just finished a green screen job where the experienced DP shot all the elements with a diffusion filter because "it would match the rest of the show" Yikes!

Keep good separation from the background and watch your spill.
Lovely.

Sean "kak key" Travers



Of course if your shooting with diffusion you should remove it for green screen work, this might sound obvious to everyone but I just finished a green screen job where the experienced DP shot all the elements with a diffusion filter because "it would match the rest of the show" Yikes!

Ah yes Sean, but the VFX sup was not on set that day, they also shot with a blue sweater in front of a blue screen, and had the FG waaayyyy out of focus.....

How to do just about everything wrong? If they were shooting on HD rather than film. they probably would have turned on detail just to cap it off.

Same Dp, same show, a huge scene with "dead guys as holograms".

Difference keying was the main tool to be used. Dp shoots like the dark hole of Calcutta to "match the rest of the scene". There is more noise that signal for the keyers to find.

We roto for weeks. Could have keyed it and timed it down so easily....

What a waste of resources! VFX sups exist to think holistically.....

DoP's exist to create the best images.

Sometimes the "best" images are not the obvious ones, or even the ones that look good in camera. They are the images that create the best show when finished?

Back to lurk mode now.

Dermot Shane
Vfx guy
Vancouver, Canada & Shanghai, China



Gotta disagree with some of this, some is great primmer for B/G screen shooting....

Jeff Blauvelt...

You want your subject to have the same look as he does on the rest of your sets or locations.

Dermot...

True but do look out for matching night shots on a stage, in this case it is better to have enough exposure in the FG that we can use the tools we have to extract matts, then we can time the shot down to match the scene, but to create a noisy mess does no one any good when we are fighting for the best comps, again we can add noise to suit...

Jeff..

Detail is probably the only variable you would want to consider altering, but usually it is already turned lower than the factory setting so you might only lower it further if you have done a test and the compositor is having trouble with the edges.

Dermot...

On this I would disagree - start with detail off, we can always add it in the comp to match the BG plates, and the rest of the scene

Jeff...

Although detail can be added in post, the most subtle and best controls are in the camera.

Dermot...

Again I would respectfully disagree, I would argue that for compositing we can do a very detailed job of adding detail both are an fairly straightforward addition to the signal chain, and in either place, can range from subtle to horrible - depends upon the artist and DOP - not the tools - those work in both cases, but using detail in camera adds a layer of trouble for compositors and gains nothing ( unless the post house is giving you a kick-back)

Jeff...

For under $500K budget features film out is not a given, and HD shot without any detail looks too soft on most displays whether CRT, LCD, Plasma, DLP or DILA projectors.

Dermot...

So use it for the show, and turn it off for VFX, we can add it to match.

Jeff...

Shooting with detail on but the level set down to -35 to -70 is an area of good compromise. With detail on you can use skin detail softening, with it off everything is soft.

Dermot...

Why create needless compromises?

Jeff...

If possible choose your compositor before the blue screen shooting days begin. The first day you can take a tape from the studio, race across town to a post facility, and in an hour capture the good takes on a non-linear HDsystem and copy the HD data to a Firewire drive.

Dermot...

VFX sup on set is a far better idea....

Jeff...

Then test individual frames on any Mac or PC with After Effects, Combustion, Shake or other software. Primatte and Ultimatte plug ins are popular.

Dermot...

Sooner or later you will find a shot that will work with one keyer,but not the others, that said - Primatte is generally looked upon a "keying for dummies" with very limited controls and Ultimatte is far past it's sell by date - Keylight is a good tool. as is BCC's two way keyer, Zmatte has a place, and Discrete's keyer is awesome, as is DS/Nitris Blue/green keyer, but you really need most of these at hand

Jeff...

If you can afford a second hour on the non-linear HD system your artist could do his tests with full motion.

Dermot...

Quick "close" keys as a test is deceptive, there is a huge step from a "quick" key that looks pretty good, and a finished shot although I can come up with something that look "good" on monitor in 5 minutes or less, you are fooling yourself if you think that you will gain any useful information through this process, other than eye lines, and lighting matching.

I almost never finish a shot with only one keyer, usually end up with two or three, often many more, takes hours, not minutes to do good work, animating masks alone is time consuming....and it is only as good as the weakest frame, would never allow myself to be put in a position where I had to sign off on a shot in a 2 hour session, that is entirely unrealistic and unfair to the artist

As always it's only my 2Cents....I have compiled a hell of lot of shots tho...probably over 1000 in the last few years in HD for HD alone, all with detail off always...always...always....every single time...

Dermot Shane
Vfx guy,
Vancouver, Canada, & Shanghai, China



And with a Panasonic?

>I've got a green screen job coming up that will be projected standard def at Madison Square Garden.

>Any tweaks any suggestions?

Jeff had good info.

Nick Hoffman 600 DP (Westport) NYC



Shot Blue Screen with f900 yesterday. With detail and matrix off, it didn't seem prudent to fuss with anything else. 24fp because the director likes it. As the efx guy was also the director, he approved all on a 20 inch Sony monitor. Client, Warner Bros., watched a down converted 14 inch. Interestingly, we shot 16x9, for a 4x4 TV delivery, because efx apparently gets more info that way, and he can repro images to his liking.

I did use a full O rim on one side, not because of blue spill, but aesthetically it seemed to help the look.

The Composite Components blue paint was great, and easy to light with 6 5K's spread with 250 diffusion. The hard part was keeping the Cyc under key, dropping doubles in but still hovered around f2.8. The spot should be out next week, it's a Looney Tunes ad, apparently trying to save the film, with kids interacting with plates from the feature.

Thanks to all for advice and suggestions...

Howard Wexler