Exterior Green Screen & Film Stock

I have the following problem: I am doing a MOW with some green screen work, especially one big exterior SFX sequence: It`s a kind of "time frozen" set-up, that means some people are frozen and others are acting around them. The shot is on Super 16 (SR 3 Advanced) and I intend to do all the exterior stuff on 7246 Daylight, filtering with Schneider Coral to warm it up and Schneider Classic Soft Filters.

In this special sequence I have "angels" talking inside a "frozen" car with a "frozen" driver. Outside the car will be "frozen" rain, created digitally. So I have to do passes with greenscreen backings outside the car. I would normally light a greenscreen 1 to 2 stops under key, but if the greenscreen is lit by the sun or an overcast sky, it would be much brighter than anything I could pump into the car. Should I cover the whole setup with a black solid and light the screen separately ? Or should I try to get as much HMI-light into the car, trying anyhow to give it a non-lit-look ? And what about the 7246, two stops underexposed in the green area, will it become too grainy ? By the way, the VFX people were suggesting a greenscreen...

Markus Fraunholz, BVK

A few thoughts from a greenscreen nerd.

Especially in 16mm, shoot with a clean lens - give your compositor a chance

Consider facing the greenscreen to the north (if you are in the northern hemisphere) which will keep it from getting lit with direct sunlight. If you are trying to emulate rainy day, you can then control the light on the car to minimize hi-con sunlight bits from blowing the illusion

I would not normally light a greenscreen two stops under key, but the best way to nail the best exposure for the greenscreen would be to shoot a few frames of test at various ratios so the post house can pick what THEY like the best...they are the ones who have to pull the matte. Where you expose the green will be different depending on which green it is and what you are lighting it with.

It is not clear whether the scene involves a lot of outdoor stuff or just the stuff in the car itself. For the stuff in the car, you can control the green contamination pretty well... for the outdoor stuff, you will want to do your best to minimize the green bounce coming back on your actors, blocking the unused portions of the screen with black fabric draped on it at the screen (reducing the soft green source) not just flagging near the actors and/or the car.

Mark H. Weingartner

VFX, Photography & Lighting for Motion Pictures & Television

LA Based

I've found keys work best when the screen is lit to the same stop as the key, but you should certainly test and offer the footage to your Compositor to see what is preferred. Also, please shoot a few tests with the filters. Diffusion can make mattes quite difficult to pull. Perhaps you can emulate the filter's effect in post so that matching your filtered, non-composite shots.

Leo Ticheli

Director/Cinematographer

Birmingham/Atlanta

Sometimes a bluescreen is preferable in exterior locations because the natural UV light will help make it "pop" without any help.

However, since you are shooting on super-16, greenscreen is far more preferable since the green record has far less grain in it, and that is a major consideration in terms of your shooting format.

There is a Kodak stock called FX214, but I don't know if that comes in a S16mm format. Basically it was developed as a low-grain stock for bluescreen and greenscreen work. As a by-product of the grain reduction, it has less apparent sharpness than other stocks, but digital sharpening at the composite stage can more than make up for anything the stock lacks.

With regard to your lighting, a good friend told me a trick which seems logical:

Basically if you stick a white card in your key light, and view it against the greenscreen through a "forest green" (or similar) filter, the white card should disappear against the greenscreen. (Placing the exposure value of the greenscreen mostly in the shoulder "headroom" of the film's tonal range.)

You should be able to do this simple test fairly quickly to determine how much light you really need to pump into the car. Alternatively you could use large silks to cut the exposure to the greenscreen, or you could shoot all of the greenscreen work on a stage, and then you don't have to worry about lighting conditions throughout the day, and how they affect the foreground contrast and greenscreen brightness.

I think Tiffen also makes a "greenscreen" viewing filter which supposedly works well, but I haven't used it, so I really can't say how well it works.

Rachel Dunn

DoP/VFX

Los Angeles

>Should I cover the whole setup with a black solid and light the screen >seperately?Or should I try to get as much HMI-light into the car, trying >anyhow to give it a non-lit-look?And what about the 7246, two stops >underexposed in the green area, will it become too grainy ? By the way, >the VFX people were suggesting a greenscreen...

Nearly all my effects work has been in commercials; and of course techniques and equipment vary from post house to post house, so what I say might not apply to your situation. You should certainly be in contact with whoever is going to be in charge of pulling off the vfx from the post end, and having VERY SPECIFIC discussions about how things should be done. Though if this is a person from a purely postproduction background you may find very little help or even understanding there. But you have to try!

Now, my own opinions:

1. I think 7246 is NOT the best stock to use in this situation. I shoot it quite frequently in fast-moving semi-documentary situations because of its speed and ability to handle mixed lighting situations, ie daylight and fluorescent. However this ability to deal with mixed colors is one reason why it is the wrong stock for greenscreen. The overlap between the blue and green dye layers actually make it harder to pull a clean matte.

Also 7246 is not a fine-grain stock, in fact it is somewhat grainier (and less sharp) than 7274, the nearly equivalent speed tungsten stock.

I would recommend 7248, Eastman's old standby 100 ASA tungsten stock. An Eastman engineer told me they haven't replaced it with a new Vision stock because they haven't been able to improve it yet! It's sharp and fine-grained and should hold up well in the post process. It's awfully easy for grain and noise to build up in 16mm, no matter how perfect it looked in dailies, so I believe in starting with the cleanest image possible. If you can't afford the stop loss of an 85 filter an LLD might be helpful, at least it would remove the worst of the UV. But you're shooting exterior, so surely 64 ASA is workable.

2. I would think controlling the light hitting the greenscreen is going to work better than pumping lots of light into the car. If rigging an overhead tent is not practical (and I'm not sure how big your shots are), can you angle your setups and the screen so it is not getting direct sunlight? If the sun was over/behind the greenscreen you'd have the greenscreen underexposed and your action backlit, which could be nice.

3. If it's possible to test the greenscreen exposure, even 100' in a Bolex, through the post process, that would be very helpful and could save you many heartaches. Though green in nature always records darker and needs exposure help, greenscreens (and bluescreens) are so saturated that they can stand to be underexposed without becoming grainy. I usually end up with 2 stops under from my Minolta spot meter (which I know is not completely accurate on the greenscreen) 1 stop under by incident meter.

4. Another reason to do a test is to get a dialog going with the VFX people, to give everyone something concrete to deal with. I am not being sarcastic when I say that politics are very important here. It's vital to create the impression that this is a team effort and the photography and visual effects people are working TOGETHER; otherwise it's very possible for things to become factional. If you establish yourself now as a leader and reach out to them to understand their needs you will be in much better shape later on. It's a film production, there is always something to complain about. If you are a friend and colleague to the VFX department, they are less likely to complain about you!

Alan Thatcher

Chicago

Years ago I helped put together a commercial with a massive greenscreen against which was shot a stagecoach, horses and all going full tilt down a dirt road.

I'm not sure where you are shooting, but this time of the year the days are getting longer. We were shooting in Arizona so sun was less of an issue than wind. We ended up attaching the frame for the greenscreen to the semi trailers of the lighting and grip departments. Attempting to light the screen would have been cost prohibitive so we went with more natural light.

As I recall, the screen was far enough away from the subject that we didn't have to deal with shadows on the green screen. As for stock I believe we shot 5245 as the grain was very tight. I don't know what color the car is you are shooting. Be warned that yellow paint very often has a large amount of green in it. Of course, some yellows tend towards orange. Have you thought about what's going to be under the car? Some like to use a sacrificial piece of greenscreen and others prefer silver mylar.

Chet Simmons

Las Vegas

I like shooting greenscreen outdoors. These are my preferences in this situation:

First of all, no diffusion ! A light coral shouldn't be an issue however I would minimize the number of filters.

Use the sharpest primes you can get, no zooms if possible.

Have your subject completely within depth of field however it is good when greenscreen itself is not sharp avoiding blemishes in the screen.

If you use the wall of a building facing north to put your greenscreen on, it would not have direct sun and it would not blow in the wind all day. The top of the building would block direct sun as a back light keeping a "rainy day" look. (unless the strong backlight is part of your look). I don't believe that you have to use strong back light in greenscreen as long as you are careful with green contamination on the subject. Cover the greenscreen as much as possible with black or white creating soft highlights or dark where you don't want it.. Have green in only behind your subject as much as this is possible. Above the greenscreen have some white background to avoid green contamination.

Another great help with avoiding contamination is using a good polarizer as long as you have enough light. Be careful not to under expose with it. Grain is the matte's enemy. Oh yes, Don't use smoke. (You knew that one, didn't you? ;-)

For your car interior. If you are planning on using long lenses I would prefer blocking light and using a small greenscreen (no pola ;-). It would give you much more control and be better for the actors. A bluescreen will suck up more of the light and it seems as if post houses are used to green these days.

Hav ethe subject as far from the greenscreen as possible.

Greenscreen exposure: If I am using a highly reflective screen like the "digital green" I will underexpose a stop however if it is a bluescreen I would expose at key. It depends on the quality of the color. If it is a darker green cloth like felt I would not under expose.

Stock recommendations:

7248 or 7274 with 85 filter is a good choice. If you don't mind the higher contrast, I would recommend 7245. It is as clean and sharp as you can get. For your exterior shots, I would rate it at 32 ASA. This stock has a minor green cast to it however it is easily corrected.

You could always use the Vision 200 only for the car interior.

Guy Livneh, DP

Los Angeles

http://www.liquid-light.com

Rachel Dunn wrote:

>Basically if you stick a white card in your keylight, and view it against the >greenscreen through a "forest green" (orsimilar) filter,the white card >should disappear against the greenscreen. (Placing the exposure value >of the greenscreen mostly in the shoulder "headroom" of the film's tonal >range.)

Rachel

I don't understand your friend's trick Ð what are you actually saying here - is there any way you could explain it better for those of us ( namely me ) who are a bit slow , because I don't see how this can actually help.

Matthew Woolf

>I am doing a MOW with some green screen work, In this special >sequence I have "angels" talking inside a "frozen" car So I have to do >passes with greenscreen backings outside the car.

Try angling the green screen so that the frame is tilted toward the ground, instead of completely upright. This would make the screen act as its own "topper" keeping the direct skylight off the green surface. Even tenting it down further will be easier than trying to "over-light" the foreground. Worst case, use ND gel on the car windows behind the actor to knock down the green levels.

Joe Di Gennaro

Director of Photography

Sherman Oaks, California

Make sure you get a Composite Components Greenscreen. Shoot only 7245. Use only prime lenses. Lose both the coral filter and any diffusion on the lens. Expose the greenscreen at its reflective value

Keep your fingers crossed, 16mm is not the way to do this.

Dave Satin

SMA Realtime, Inc

>I've found keys work best when the screen is lit to the same stop as the >key, but you should certainly test and offer the footage to your >Compositor to see what is preferred.

Great points on all the posts regarding an exterior green screen. I would like to add a few observations I don't believe were mentioned yet.

If using a fabric greenscreen be sure to back it with black so the sunlight doesn't bleed through. I have seen creative gripping which mounted a 12x12 or 20x20 frame onto the side of a pickup truck. This enabled the screen to be easily moved into the correct position and the truck weighs it down for the wind. With a little rigging forethought it can be tilted down to a suitable angle for less direct spill.

I have found screens to be underexposed 1 stop to work best. And the important relationship is the screen exposure to the shooting stop, not the key light stop. They can often be different.

Jim Sofranko

NY/DP

>Make sure you get a Composite Components Greenscreen Expose the >greenscreen at its reflective value

I have used the composite components greenscreen with Kodak's SFX 200ASA film stock and tests revealed that one stop under exposed (reflected - Spotmeter F) was the best when transferred on the Spirit to D1.

And our SFX supervisor had said "I told you so".

It resulted in a deeper green as opposed to a brighter and paler green. They both worked however it was easier for the Post house when we under exposed.

Guy Livneh, DP

Los Angeles

http://www.liquid-light.com

<Expose the greenscreen at its reflective value

Dave wins my prize of the day. There is a reason why these things are made a certain color. Too many times I see people illuminating screens till their color saturation is far from what it was original intended hue is suppose to be. While nowadays cutting screens has become easier I think it's also important to try to maintain the screens color integrity. It sounds quite different from what I've been reading here, but I work from the screen backwards to the talent since the screen is as important in this case as the talent. I think too many times folks look at it as just a screen we need to light and don't realize that if it ain't right, everything including your talent may suffer.

And one more suggestion, I might consider a blue screen for outdoors rather than a green screen. In addition, I might want to test before using any coral filters. I'd probably drop the filters in this case since once again this is about maintaining the integrity of the hue in the screen. I think placing the screen in a direction where it is hit only by ambient daylight and not skylight is going to give you an even tone and a level that is workable with the talent. And even more reason to use blue rather than green.

Some might scream that your going to have a problem with screening 16. I think that's a bunch of crap. I've successfully screen many a 16 projects without a hint of problem.

Walter Graff

NYC

Matthew Woolf wrote:

Rachel Dunn wrote:

>Basically if you stick a white card in your keylight, and view it against the >greenscreen through a "forest green" (orsimilar) filter,the white card >should disappear against the greenscreen.

> Rachel

> I don't understand your friend's trick - what are you actually saying here >- is there any way you could explain it better for those of us (namely me) >who are a bit slow , because I don't see how this can actually help.

When you are keying a greenscreen, you want to be able to separate out as much of the tonal range of the foreground as possible.

This is done mostly by conparing the relative luminance values between red, green and blue. If you are looking only at the green record, a properly exposed greenscreen should look like a black and white picture of your foreground subject against a white background.

Depending on how much red and blue your greenscreen material reflects, those records should look like the foreground is against a dark grey.

If you over-expose or under-expose the greenscreen this can affect the quality of the edge detail as the green will either bleed into the foreground or the green channel will not have enough separation to easily isolate the edge of your foreground subject.

By placing a white card in your key light, and looking at it through a deep green filter, you are blocking out all red and blue light reflected off of it - the same thing that the green colour of the material in your greenscreen is doing, and the same thing that your film is doing. So, if you change the lighting ratio until the white card is indistinguishable from the background, you are placing the greenscreen exposure at the white point (zone 8-9) on the green record of the film, and you can easily see this without the distraction of the red and blue light being reflected from the white card.

Many meters are calibrated to give the exposure of an 18% grey card, so they must take into acount the difference in light intensity between red, green and blue, and the difference needed in light intensity to properly expose the green and blue layers of the film. Because of this weighted exposure, metering a pure green or pure blue subject is going to fool your meter into giving you a false reading - hence the under-exposing that many DP's do.

By using this method, you can easily get a visual confirmation of the correct exposure - it will definately get you in the ballpark. You'll probably end up under-exposing by a stop or two, but if you're a less experienced DP, you probably won't have to burn as much film to get there.

Rachel Dunn

WalterNY wrote:

>I'd probably drop the filters in this case since once again this is about >maintaining the integrity of the hue in the screen. I think placing the >screen in a direction where it is hit only by ambient daylight and not >skylight is going to give you an even tone and a level that is workable >with the talent. And even more reason to use blue rather than green.

Excellent points!

Definitely drop the filters - they will change the colour of the green screen and make it harder to key. Remember, you are going into the digital world, you can make it any colour you want. Even a digital pro-mist is easy to do.

UV light will make the bluescreen pop in indirect light, so it is generally a better choice for outdoor shooting - on 35mm where grain is less of an issue.

However, shooting on s16, bluescreen will give you grain problems. A UV filter may help keep the colours truer on a greenscreen, and might make it slightly easier to key, but that's minor compared to the grain thing.

Rachel Dunn

Thank you very much for all your extraordinary advice !

I am now sure, the best thing to do is a test...,to get into a concrete situation and get facts, I can talk about with the post-people !

That`s what I conclude from all of your messages:

- I will NOT use 7246

- I`ll use 45/48/74 or FX 214

- not use any diffusion

- not use Corals (except when I`m shooting tungsten stock)

- I«ll face the greenscreen north and put a black solid behind it and tilt it down until the appropriate exposure

- if it`s still too bright I`ll put NDs on the windows of the car (very good idea ! )

By the way, I exclusively use prime lenses for 16mm and I owe a set of Schneider Filters (costed a fortune) with MAXTRAN coating, which are superior to ordinary filters...Thank you again for your overwhelming interest !

I dont believe that sfx 200 is slit to 16mm widths.

I find that when working in 16mm, shooting 7245 outside, that the reflected reading off of the composite components green screen will yield optimal results. And yes, have the grips back the screen with a white white/black griff, or something else opaque

Note that I am being EXTREMELY specific here:16mm, composite components, 7245, etc.

Dave Satin

Director of Engineering

SMA Video Inc.

>Make sure you get a Composite Components Greenscreen. Shoot only >7245 Use only prime lenses. Lose both the coral filter and any diffusion >on the lens. Expose the greenscreen at its reflective value.

What Dave said.

Especially about the filters. Forget filters. Add them later if you want them.

Putting any color filters (aside from compensating for daylight) or any diffusion whatsoever on or behind the lens is a good way to ensure that you will have lots of problems pulling the mattes later, especially on 16 where you are already starting with the water up to your chin.

Bob Kertesz

BlueScreen LLC

http://www.bluescreen.com

Alan wrote:

>"I would recommend 7248, Eastman's old standby 100 ASA tungsten >stock. An Eastman engineer told me they haven't replaced it with a new >Vision stock because they haven't been able to improve it yet!"

Here-Here! 48 is one of my all-time favorite stocks. I'm not surprised it's a tough one to improve.

Illya Friedman

Camera Assistant

Van Nuys, CA

I recently received some info on this product. Maybe worth checking out! Formatt Filters claims to have developped a green screen filter called "Procomp" which is apparently specially designed for green screen applications. I've never used them, so I can't vouch for them, but perhaps someone else has had experience with them.

Perhaps the people from Formatt can shed some light on this?

Danys BRUYERE

Groupe TSF, Paris

>A few people noted that one should underexpose a screen by a stop or >two. I have a thought, but before I make it I wanted to hear why they say >that.

Assuming non colored, non-color gelled lights hitting the screen:

I like to see the Composite Components Digital Green Screen and Digital Green Paint underexposed from key by half a stop to a stop - no more than a full stop down maximum, and of course lit flatly to a gnat's ass edge to edge.

That particular screen has high luminance bounce-back because of the phosphor dye formulation they use (and green, of course, being 59% of the color signal). By underexposing it slightly, it retains a good amount of saturation. Most matte extracting processes rely on color difference amounts (how much higher is the green value than the blue?), and so having good saturation is often more important than the high luminance level. And of course there's the added bonus of having less bounce and wrap on the foreground objects.

This applies only to the Composite Components Digital Green Screens and Paint, not to the endless remarkably poorly done so-called digital screens and paint out there, and not to blue screens or paint from anyone. I like the CC Digital Blue Screen and Paint at stop.

Disclosure and disclaimer. The people at Composite Components are my friends, and I own a couple of their screens and recommend their stuff to anyone who will listen because their stuff works really, really well, but I can't be bought. I can, of course, be leased or rented short or long term by anyone at all.

Bob Kertesz

BlueScreen LLC

I posted on this thread last week after having just done a greenscreen shoot in 16mm. I advised shooting 7248 (which I did) and underexposing the screen (which I did, -1 stop incident).

Yesterday I was at the post house to see the nearly-completed Flame work from my job. The shots look just like I wanted, they did a beautiful job with the backgrounds, and everyone is very happy with the results. Most importantly, and I'm not kidding, our subject was the President/CEO of a large company, he looks great, and was happy because we were done with him in half an hour!

I have shot some things for this compositor before, VFX work where he was directing, and he's one of the few post people I've met who thoroughly understands shooting as well, so I asked if I could have done anything different on this shoot to make his work easier. He said that he would have preferred the screen somewhat brighter, perhaps a half-stop. There was no problem in the final product, but he did have to work a bit harder to get there. Mea culpa! I have to admit that I had not talked with him before the shoot, though it came up so quickly I'm not sure he was hired yet anyway. Even on a simple shoot like this it's possible to make things better, and I should have taken that little extra step.

While there I grilled him about blue/greenscreen issues in general. Here is some of what I gleaned:

-Much of the blue/greenscreen work he sees is very difficult to work with, even from supposedly top directors and DPs. Very few DPs make the effort to communicate. This results in things like the shoot where he recently visited the set to find the greenscreen being shot on 5277--a low-contrast stock very difficult to pull a matte from. No wonder some post guys get the attitude of 'Do what you want, we can fix it later!'

-*Some* underexposure is usually fine on green, less so on blue. I have been one of those who worked on the theory that with more saturation (color difference) you didn't need as much luminance in the screens. This has the added benefit of less 'kickback' of screen color onto the foreground subject. But this is *not* always the way to go. Especially in 16mm, especially with blue, both of which increase the likelihood of grain/noise turning up in underexposed areas.

-Every system and every compositor's needs and preferences will be different, so *communication is essential* and for longer, bigger projects *testing is ideal*.

-He has a personal preference for the pre-Vision stocks still available, '48 and '98, obviously the latter only for 35mm. He finds the edges on the Vision stocks harder to work with (which is counterintuitive because they have higher acutance) and doesn't like their inherently lower contrast. I didn't ask about the special FX stocks. However, as he said, he is almost never asked his preference by the DP.

-I asked about 7245 for matting in 16mm due to its fine grain, even finer than 7248. He didn't have any experience with it. My concern would be the 'crosstalk' between the green and blue layers since it's a daylight stock. Dave Satin voiced a strong preference for '45 if compositing in 16, and if the crosstalk isn't an issue that would be a good option to know about.

So a week after posting on this thread I'm more cautious about the underexposure I recommended. But I'm more sure than ever about this: talk with the post people.

Alan Thatcher

Chicago

I had another meeting with the VFX people, taking care of my MOW, AFTER I received all the informations from you in this wonderful forum. With a very innocent face expression I aked them, which stock they`d

Prefer for the composite work. They looked at me and said (or asked...) Uhm, 400 ASA? I replied, that we are doing a Super 16 feature, and if "400 ASA" would be the right thing, concerning grain ? They again looked very helpless, and I then promised to do a test to find out the best stock... That was a great relief to them... I`ll tell you how the test worked

Markus Fraunholz

> -He has a personal preference for the pre-Vision stocks still available, >'48 and '98, obviously the latter only for 35mm. He finds the edges on >the Vision stocks harder to work with

I often find that post people (and I do consider your compositor a post person, even if he has on occasion directed) overlook the most obvious variable in the material they get, and that's the telecine transfer. Quite frankly, I would take their comments on stocks and their "preferences" regarding such with a huge, huge grain of salt, because unless they're working with film scans (and if you're doing commercials, they're not) what they're getting in influenced very little by the stock choice, but very largely by the colorist's choices when it's transferred. Many differences they think they've seen are more likely differences in the choices of the colorist and/or the clients present in the telecine room at the time of transfer. Realistically, the colorist would be the only one in post who could actually voice an informed opinion on the differences between stocks when shot by the same cameraman and transferred on the same telecine equipment.

You and others mention that "testing is ideal" and that one should "talk to the post house prior to transfer." I would contend that while this can sometimes prove valuable, it's much more valuable to follow known proper shooting procedures (known to cameramen, not necessarily to compositors) and provide elements that can work. My experience is that at least 75% of all "problems" in green and blue screen elements originate in the telecine room and not on the stage or in the lab. And for me, the apparent fact that 5 different post facilities and 5 different compositors will "ask" for 5 different things proves the point.

Mike Most

VFX Supervisor

IATSE Local 600

From: D Oldis < SIZE=2 >doldis@triad.rr.com >

Michael D. Most wrote:

>I would take their comments on stocks and their "preferences" >regarding such with a huge, huge grain of salt, because unless they're >working with film scans (and if you're doing commercials, they're not)

Several years ago I made a TV spot that required only one bluescreen shot. Since it was fairly straightforward I decided during preproduction to do the composite work myself using my Media 100 system and After Effects. I purchased Ultimatte's plug-ins expressly for the job.

We shot the project on 5274/200T. We used bluescreen instead of greenscreen because there was a lot of greenery around the actors and they were wearing green army fatigues. The 20' x 20' bluescreen came from Composite Components. We used an ARRI BL4s with a Cooke 20-100 zoom. We shot at T4. There was no filtration. We were on a soundstage and everything was lit with tungsten. The bluescreen was lit to T4 based on reflected meterings. We keyed our talent with dual 3/4 backlight--a 10k on one side and a 5k on the other. We augemented that with soft fill from the front and above. The cyc lights illuminating the bluescreen were gelled with 1/2 CTB. The actors were about 20 feet from the bluescreen. There was no spill hitting the talent.

We transferred the film to Digital Betacam at a post house in Atlanta. Then I brought the Digi-Beta master back to my editing suite in North Carolina and digitized the footage onto the harddrives. I opened the files in After Effects and applied the Ultimatte plug-ins.

Well, surprise, surprise... I couldn't pull a clean key to save my life--there was a strange green edge on one side of the actors and a magenta edge on the other. I ended up rotoscoping the material by hand, drawing feathered masks around the foreground elements one frame at a time. It took an entire day but I finished the project on time and the spot hit the air the following week. It looked great and the clients loved it.

Afterward I called around to see if anyone could explain why my original plan hadn't worked. I talked to Media 100, Ultimatte, the transfer facility, and Kodak. They all had different explanations. For instance: "It's a known fact among colorists that you can't use the 5274 for keys--that's why everyone uses '93!"; "Zoom lenses aren't sharp enough for bluescreen or greenscreen work--you have to use primes!"; "You overexposed the bluescreen by a stop"; and "Your lens was bad--it had chromatic aberration problems."

A few days later I took the negative to a friend at a service bureau that does print work for a lot of ad agencies. He scanned a couple of frames on a drum scanner at 4k by 3k resolution then put them on a zip disk as uncompressed RGB PICT files. I returned to my edit suite, opened the files in After Effects, applied the Ultimatte plug-ins, and voila! I had the cleanest mattes I'd ever seen.

What's the moral of this story?

There are a lot of variables between the lens and the finished project when it comes to composited material. My advice--which echoes Mike Most's posting--is to do your composites using uncompressed scans at the highest resolution you can afford. If you're doing TV spots, you're in luck because commercials are so short you don't have a lot of footage to deal with. You can rough edit the spots first. Then when you know which shots you're actually going to use, have those frames scanned, composited, and added to the final cut. You can scan at 4k or 2k or whatever you want, then resize the files in After Effects (or equivalent) to 640 x 480 pixels for output.

I also learned that 5274, a bluescreen exposed as if it were an 18% gray card (using a spot meter), and a Cooke 20-100 zoom work perfectly well if you're compositing with scans.

D.A. Oldis

Director/Cinematographer

Winston-Salem, NC

Mike Most wrote:

>I often find that post people (and I do consider your compositor a post >person, even if he has on occasion directed) overlook the most obvious >variable in the material they get, and that's the telecine transfer.

Point taken, however this particular guy worked until recently at a post house with in-house telecine, so he personally supervised the transfer of most everything he worked on. And he's not the only one to dislike the Vision stocks for compositing; isn't that why EK came out with the SFX stocks?

>(...) it's much more valuable to follow known proper shooting procedures >(known to cameramen, not necessarily to compositors) and provide >elements that can work.

Well, it can be a crapshoot. Markus, the DP who originated this thread, asked his post folks what stock they would prefer and they, amazingly, suggested ''400 ISO' apparently forgetting the project was originating in 16mm! Or, more frighteningly, not understanding why that might call for some special consideration.

However what they're now doing is testing and if that's carried out fully they should arrive at a process that will allow him to shoot efficiently and deliver them elements they can work on efficiently--to the degree they're able.

The testing process works to everyone's advantage; clearly the post people need to get up to speed fast and this will get them a jump-start. And Markus will be exempt from any finger-pointing later on because he has consulted with post from the beginning. Testing and talking are as useful for team-building as for actually setting up work methods.

One key reason for consulting with post is the wide variation in the transfer you allude to, Mike. I would certainly include the colorist as a key, maybe THE key, member of the post team.

Obviously, sometimes, what post asks is unrealistic, even absurd or flatout wrong, as Markus found. But, having asked the compositors, at least he now knows he's dealing with people who are clueless, and he can take steps to right the situation...and cover his own ass. 'Knownprocedures' only help if you're dealing with people who know them, and Markus' post team may not.

So what if they have to reinvent the wheel, as long as they reach their destination....

Alan Thatcher

Chicago

The answer, by the way is that you were transferring on an Ursa or similar telecine, and you were experiencing afterglow corrector artifacts in your footage. Always make sure that you transfer on a telecine with ITK head amps TWIGI, etc. If you REALLY want your footage to turn out great, then use a Millenium.

Dave Satin

Executive Vice President

Director of Engineering

SMA Video Inc.

www.smavid.com

Dave Satin wrote :

>The answer, by the way is that you were transferring on an Ursa or >similar telecine, and you were experiencing

afterglow corrector artifacts in your footage. Always make sure that you transfer on a telecine with ITK head amps TWIGI, etc. If you

REALLY want your footage to turn out great, then use a Millenium.

Sounds good, but without at least a bit of quoting I'm not sure what you're replying to...I don't think it was to my initial 'follow up' post. (Not that Lyris makes that easy...I bet it bounces this post back to me.)

I did have a specific question for you, Dave, about blue/greenscreen on 16. You indicated 7245 was the best stock choice, and I understand why its sharpness, granularity, and also its contrast would be ideal. But is there any problem with 'crosstalk' between the blue and green layers since it's a daylight stock?

Alan

5295 and 7292 were one of the first Kodak stocks to use T-grains in one of the color layers. The introduction of the EXR line, with T-grain in all layers, meant that 5295 could be obsoleted by 5296 (EXR 500T.) At least, that's how I understand it.

As for Vision stocks being too low in contrast for good green/bluescreen composites, that sounds a little bogus. After all, Geoff once mentioned the great composites he was getting with material shot Fuji F-400T, and that's even lower in contrast than Vision 320T. I would think the finer grain and greater sharpness of the Vision line over the EXR line would make them even more optimal for effects work, not less.

David Mullen

Cinematographer / L.A.

Mark Weingartner wrote :

>As for Vision stocks being too low in contrast for good green/ >bluescreen composites, that sounds a little bogus.

Yeah...it seems we managed to do process work on vision stocks on MI2, Vanilla Sky, MIB2, (to mantion a few) and hundreds of thousands of feet of commercials, so I would have to agree with Mr. Mullen on this one:-)

Other people managed to get away with it on a few other movies too.

Likewise, while I love Jonathan Erland's Composite Component screens, we have also managed to pull the odd matte or two using other fabrics now and again (see aforementioned list as the tip of the iceberg.)

There are times when the "tooth" of the Tempo cloth materials is advantageous... ...and once in a while, we even end up using paint when that is appropriate.

All that said, however, 16mm give you much less leeway than 35mm or Vista vision, and I would not make more specific recommendations than I did earlier absent more information - too many variables.

Usual disclaimers:

Jonathan Erland is a friend, but I have no financial arrangements with him. Dazian's never pays me when I use tempo cloth. Neither of the two major purveyors of narrow band fluorescent tubes and fixtures has any financial arrangements regarding the use of their products

EVERY SINGLE POST HOUSE ON EVERY SINGLE JOB PICKS DIFFERENT DENSITIES FROM THE ONES THEY OR SOMEONE ELSE PICKED ON THE PREVIOUS JOB - AFTER SCANNING TEST WEDGES THAT ARE ONLY LABELLED WITH SLATE LETTERS AND NOT WITH WHAT THEIR NOMINAL EXPOSURE IS.

If you look really hard, you might find a lesson in that :

Mark "lit a couple of blue/green/red screens for digital compositing"Weingartner

Mark Weingartner wrote:

>EVERY SINGLE POST HOUSE ON EVERY SINGLE JOB PICKS >DIFFERENT DENSITIES FROM THE ONES THEY OR SOMEONE ELSE >PICKED ON THE PREVIOUS JOB - AFTER SCANNING TEST >WEDGES THAT ARE ONLY LABELLED WITH SLATE LETTERS AND >NOT WITH WHAT THEIR NOMINAL EXPOSURE IS.

I'm curious about the test wedges. Do you shoot them of only the Green screen material? Or do you have som sort of standard object you put infront of them, for a test composite? Also in your experience, or anyone who has a bunch of greenscreen experience, Are there compensations to be made to the greenscreen exposure based on the foreground object? I.E. Someone wearing a light colored dress, as opposed to a dark (red) dress, or Mid town jsacket opposed to a Black leather Jacket? Also What about skin tone? I'm just curious if you have to make adjustments, or is it the case that once you and the post house pick the Greenscreen exposure, then how the foregropund element is exposed (or what it consists of) is not an issue.

Steven Gladstone

Cinematographer - Gladstone Films

Better off Broadcast (B.O.B.)

New York, U.S.A.

>Also in your experience, or anyone who has a bunch of greenscreen >experience, Are there compensations to be made to the greenscreen >exposure based on the foreground object?

I treat the greenscreen as a separate element yet one related to the foreground. First off, I light a greenscreen for what it is and what it's saturation is supposed to be regardless of the talent. It is the greenscreen that must be cut and I want to give the people who do that a greenscreen that is true to the color saturation it is supposed to be. I remember a few years back doing a full hardwall cyc screen for a dream sequence. Someone suggested I use regular green paint that I have matched to the greenscreen color because it was cheaper. I told them there is a reason why that paint is a certain color and that color is critical to proper cuts. Sure I could find a range of colors that could work, but I'm trying to make everyone's life easy and a screen to me is it's own element that should be treated with as much respect as your talents exposure.

As for talent, I light them not necessarily related to the green screen but related to the setting they are going to be in when that element is added in the background. So in my example, it was a night exterior, the moon in the sky, a sense of a foggy night on the screen. I turned off the screen in my head once I had it lit properly and lit the talent for the scene she was going to be placed in. I gave her the blue backlight I wanted to represent the moon, softly lit her from one side depicting a soft night source, etc.

Actually many times I then turn the screen off and light my talent in limbo. I think in many ways the screen can be a detriment to lighting your talent properly and shutting it off after getting it right for me is the difference between lighting my talent properly for the scene they are going to be in in the composite and making it look like a badly lit element within the composite.

What she had on, whether it was light or dark had little to do with the screen for me in this case other than her exposure range was determined once I found the optimum range for the screen, then everything was bracketed within that exposure range. Of course, I've watch a hundred guys treat screens a hundred different ways so do what works best for you. This method has been foolproof for me.

Walter Graff

>Actually many times I then turn the screen off and light my talent in >limbo. I think in many ways the screen can be a detriment to lighting >your talent properly and shutting it off after getting it right for me is the >difference between lighting my talent properly for the scene they are >going to be in in the composite and making it look like a badly lit >element within the composite.

Excellent advice.

The eye gets easily fooled by screen bounce, and it often appears as if there is enough back/fill/top/side light, when in fact what you are seeing is screen bounce, almost all of which will be removed when the composite is made. You are then left with a much higher key to fill than you intended, and dark edges to boot. Turning off the screen and laying black on the floor (lighting your talent in limbo, as Walter said) will help prevent that sort of thing.

Bob Kertesz

BlueScreen LLC

>Do you shoot them of only the Green screen material? Or do you have >some sort of standard object you put infront of them, for a test >composite?

This depends on what we are testing. My default test includes a foreground humanoid with hair, often teased out., sometimes pieces of set dressing that are particularly spill-susceptible (brushed aluminum or stainless if it is part of the set, for instance) and tracking marker samples, if applicable.

I generally light the foreground "normally" and wedge different blue/green screen materials and exposures.

As Walter and Bob have mentioned, the screen is a separate element and what is important is the neg density of the screen, not its ratio to the foreground...though a good test should also have some underlit foreground if you are likely to have that on the set so that the post house can be reminded of the issue of spill suppresion.

I do not endorse the practice of back or edge-lighting with color complementaries - minimize your spill with blacks teased in to the edge of your matte line on the screen and let the spill suppression software do its work..

I heartily endorse Walter's suggestion of lighting with the screen off...after all, once the matte is pulled, that is supposed to be what the foreground element is going to look like, so that is what you should be lighting for.

It doesn't hurt to roll a few reference frames of your foreground with the screen off so the postfolk can see what you were aiming for.

>Are there compensations to be made to the greenscreen exposure >based on the foreground object?

Generally not.

There are other factors , including, but not limited to the prevailing luminance levels of the background plate with respect to the foreground, which may affect the post house's choice of screen densities. Sometimes they will want to skew the screen exposure one way or the other.

Mark "available as a process supervisor for shoots, weddings, and bar mitzvahs" Weingartner

VFX, Photography & Lighting for Motion Pictures & Television

Mark H. Weingartner wrote

>"...depending on which green it is and what you are lighting it with."

A question that I get asked occasionally from the rental house is "do I want digital or chroma green?" I always pick digital but I have to admit I don't know the difference. Yeah I know its something I should know. Am I choosing wisely?

Its for compositing work in film.

Norman Bonney

San Francisco

Norman wrote:

>"do I want digital or chroma green?"

A couple of thoughts on this:

1st of all, the term Digital Green is technically a trademark of Composite Components (Jonathan Erland's company) and unless the rental house is referring to his specific fabric (spandexy sort of stuff) it is not, strictly speaking "Digital Green"

That said, there are no standards concerning what constitutes what color.

There are"chroma key green" and Ultimatte Green" which are available as paint from Rosco, and there are fabrics sold by Dazians and others and sewn up by a variety of different shops that match those two colors to a greater or lesser degree. The so-called chroma key green fabrics are generally not a bad match for the paint and are pretty monochromatic. The so-called digital greens (and I am talking about the ones that are NOT originating from Composite Components) very tremendously (and not in a good way) from each other. Some of them are sort of "asparagus pee" yellow, if you know what I mean, kinda more chartreause than actually green. While these colors generally have good blue/green separation, they reflect a lot of red...this means that under tungsten light, they seem to be much hotter for the amount of light thrown on them than chroma key green... ... but they don't necessarily have a lot more green in them.

Many of my tests of most of the "so-called" digital green tempo cloths have resulted in our choosing chroma key instead for a number of different projects, but in some cases, the advantages of the so called digital fabrics outweigh the disadvantages. This is quite "case specific and material specific.

Note that if you are lighting any of these fabrics with narrow band green fluorescent tubes, the differences are much less noticable than if you light them with wider spectrum sources.

Mark Weingartner

LA based VFX guy

Mark Weingartner said:

>I do not endorse the practice of back or edge-lighting with color >complementaries - minimize your spill with blacks teased in to the edge >of your matte line on the screen and let the spill suppression software do >its work..

Is this because the back/edge lighting doesn't match the lighting scheme desired for the element, or for other reasons? Thanks.

James Wallace

DP IA669

Vancouver

>Is this because the back/edge lighting doesn't match the lighting >scheme desired for the element, or for other reasons? Thanks.

Primarily yes, you should light the foreground as appropriate for the plate it will be comped to. Additionally, Ultimatte and other systems for extracting chrominance mattes have come a long way since the late 70's, and do not need the "help"...especially when the "help" may create odd colored edges to foreground elements that then have to be treated separately.

Likewise, spill suppression has come a long way with regard to "dialing out the green/blue" from the foreground element.

Above all, talk with the post house. This is as important politically as it is technically. If they have been consulted, they can't point the finger at you without its pointing at them a bit too:-) If they recommend a complementary edge light, you might want to find out a bit more about their pedigree and experience.

Mark Weingartner

Mark Weingartner wrote:

>Primarily yes, you should light the foreground as appropriate for the >plate it will be comped to. Additionally, Ultimatte and other systems for >extracting chrominance mattes have come a long way since the late >70's, and do not need the "help"...especially when the "help" may create >odd colored edges to foreground elements that then have to be treated >separately.

Absolutely!!! If you light the edges in a complimentary color the compositor will not only have to dial out the green spill, but they will have to dial out the odd color as well.

The method I prefer of dialing out the green spill goes like this:

There is a great tool which can selectively color correct based on hue.

Using this tool, I'll suck the saturation out of the green in the image, preserving the luminance, then I'll tint this same area to a color matching the skin, or other edge color of the foreground object.

If it's a particularly nasty composite where someone might have long blond hair in a red jacket with alot of motion blur, I'll use rough soft edged garbage mattes to selectively tint areas of what was the greenscreen to match the various colors in the foreground plate (hair, skin, jacket) etc... This can be done fairly quickly.

This lets you pull a very nice soft matte with alot of detail, and not really worry about if it is perfectly laying in with the edge because if the matte is a little loose, any background showing through is the same color as the foreground object you are laying in. This is a particularly useful method for preserving motion blur and retaining every single hair which might otherwise be clipped off by other methods of suppression.

So specifically lighting edges is not necessary, but controlling spill will save you a fair bit of time in post. It can be fixed, but you would rather spend that time (and money) on making that shot better, rather than just trying to make it work.

The only time lighting the foreground object with a complimentary color will work is in a motion control model shoot where the matte pass can be shot separately from the beauty pass. In this case you are aiming for a silhouette of the model against the greenscreen, and the beauty is shot against black.

One of the things which have caused me the biggest headache is seams in the greenscreen behind hair. Please, please please, be nice to your compositor, and if you have hair blowing in the wind, make sure that it doesn't cross any seams in the green screen - even if you have to fly in a separate screen behind their head.

I know it sounds logical, but you would be surprised at the number of shots I've run across that have this problem. Removing the line through the loose hair is extremely difficult and will eat up alot of time (and your budget). (Of course I know that no one on this list would ever do something like that!) :)

If you have to have a seam, try to keep it below the neck. It's far easier to paint-fix clothing than hair. The same applies for the face.

Rachel Dunn

DoP/VFX

Los Angeles

I don't believe it's an all out 'don't use it' situation. If your trying to create a back light just to rim someone's body, I say don't do it, but if you are using it for an effect that works within the context of the green screen, then no one should have to be dialing anything. Take the moon example I mentioned. I used a low intensity blue light that spilled across the top of the persons hair without rimming their figure. IT worked just fine. I think as I said it's about two different things:

1. The green screen is it's own element. It has little to do with the talent

2. The talents lights should not affect the talent in a fashion that is going to cause problems in cutting the key. That doesn't mean you can't light people in the scene they are going to be inserted in. It just means you have to remember the edge of the person is the area that is where the cut needs to be clean so adding some kind of light that is going to affect that line might be detrimental.

Walter Graff

NYC

Quoth Walter Graff :

>...If your trying to create a back light just to rim someone's body, I say >don't do it, but if you are using it for an effect that works within the context >of the green screen, then no one should have to be dialing anything.

Thanks for the clarification...I was not trying to suggest that you avoid using color complementaries in blue or greenscreen work, only that you not use them with the mistaken impression that you are somehow "helping" the key. If the scene calls for those colors, by all means use them... just don't use 'em if you don't want to see them in the composite...then you are just adding work for the compositor.

Again, if you are trying to pull difficult live keys with a late 70's or early 80's chroma key switcher, you may want to use a hint of complementary hue ... ...my advice is predicated on "modern" equipment and techniques.

Mark Weingartner

WalterNY wrote :

>I don't believe it's an all out 'don't use it' situation. If you are trying to >create a back light just to rim someone's body, I say don't do it, but if >you are using it for an effect that works within the context of the green >screen, then no one should have to be dialing anything.

In the Example you cite, you lit the foreground so that it would be properly integrated with the inserted background. So putting a rim on the person is probably exactly what you would do if you were shooting a night exterior. That's definitely the way to go.

I thought that the other comment was talking about was using a complimentary color rim light just to get a better edge, regardless of the integration problems it might cause. Not a good thing.

Rachel Dunn

DoP/VfX

Los Angeles