New Indie Film Tech Tip: Green Screen Construction

SPaulovich · May 7, 2005

Here's a handyman's guide to constructing a low cost green screen for chroma-key effects.

A little bit of back story

I bought a green screen backdrop at a recent prosumer video show in Boston. I got a good deal on the backdrop itself, without realizing the framing hardware was, in my opinion, outrageously expensive. So I brought the backdrop home and did some brainstorming. Finally 'dawn broke over Marblehead' and I figured out what to do.

Words to live by

PVC is your friend. I can't emphasize that enough. Working with PVC is like playing with Tinker Toys (if you're old like me) or Legos (if you're not that old.) It's marvelous stuff, inexpensive, light weight and versatile.

The whole thing

Aside from the backdrop (the green thing in a bag on the left), all the parts were purchased from a local hardware store (Home Depot.) Here's the parts list:

Four (4) 10' sections of Schedule 40 PVC 1" pipe (approximately $20)
Eight (8) 1" PVC end caps (approximately $4)
Six (6) 1" PVC "T" connectors (approximately $4)
Two (2) 1" PVC 90-degree elbows (approximately $1.00)
Three (3) 1" PVC connectors (approximately $2.00)
Eight (8) hand clamps (approximately $20)

Important notes

I have no clue what Schedule 40 PVC means. It probably has something to do with thickness... but since we're really not using it for plumbing purposes I don't think it matters.

Use the 1" PVC pipe. The 1" measurement is the pipe's diameter. Remember, this structure has to support the backdrop's weight - so using anything smaller than 1" is probably not a good idea.

Pay close attention to the connector sizes. If you're working with 1" pipe, you need to get 1" end caps, 1" T-connectors, 1" elbows and 1" extension connectors. Trust me, it's worth checking the parts twice while you're at the store.

Up next: building the support feet...

SPaulovich · May 7, 2005

Part 2: Building the Support Feet

You're going to have to cut the 10' sections of PVC pipe. A hacksaw works nicely but if you have a table saw or other power saw it's going to make things much easier.

Each support foot requires:

Six (6) 1' sections of PVC
Three (3) "T" connectors
Four (4) end caps

Once you've got the parts together, lay them out like this:

This is going to make a nice wide/deep foot that will support the frame.

If you want to make this a permanent fixture, feel free to secure everything with PVC cement. I actually bought a can with the intention of using it. But you don't need it to hold things together and if it's not cemented, the whole thing comes apart for easy storage and transport.

Connect all the pieces together so it looks like this:

Repeat this whole section to make the second foot.

Don't forget the end caps. In addition to providing a professional "fit and finish" to your frame's feet, they raise the structure just high enough to run electrical cords underneath!

Up next: vertical supports

SPaulovich · May 7, 2005

Part 3: Adding vertical posts

There are a couple of things to take into consideration when adding the vertical posts to the frame.

First, make sure you know your backdrop's dimensions. In my case, the fabric was 10' x 12'.

I wanted to leave some room at the bottom to have a couple of feet flat on the floor (in case I needed to film someone walking onto the backdrop.)

Second, a couple of shorter PVC sections with extension connectors is stronger than a single piece of PVC. Shorter pieces also give you the flexibility to make the green screen taller or shorter.

So I decided to put in one 3' section and one 4' section.

Cut the vertical posts to the size you see fit. Just make sure you cut two identical sets, one for each side!

Up next: hanging the backdrop

SPaulovich · May 7, 2005

Part 4: Hanging the Backdrop

The backdrop I bought has a loop at the top through which to hang it.

Again, remember to check your backdrop's dimensions to make sure your frame is wide enough.

Again, too, multiple sections of pipe joined together are stronger than a single length. This is particularly important for the top of the frame. I ended up cutting two (2) 5' sections.

On each end of the top rail, connect a 90-degree elbow. That's what's going to connect the top rail to the vertical posts.

If you haven't started loving PVC by this time... I don't know when you will.

Once the backdrop is threaded on the top rail, put all the pieces together and stand it up. It's probably easier with two people but I managed to raise the thing myself with minimal effort.

Don't mind the wrinkles, we'll take care of that next.

Up next: setting the tension

SPaulovich · May 7, 2005

Part 5: Setting the Tension

Congratulations, you're almost done!

A flat level surface is critical in using a green screen. The slightest wrinkle will cast a shadow, making your life a lot more difficult. Trust me. (if you haven't figured it out yet, when I say 'trust me' is't because I've already taken the trouble to make the mistake in the first place!)

First off, use something moderately heavy to set the backdrop's vertical tension. Put one weight on either side. I used a couple of jack stands - heavy and stable. You're really just using these weights to stretch the fabric vertically so you don't have to go overboard.

To adjust the horizontal tension - and this is the most important aspect so take your time - you're going to wrap some of the backdrop fabric around the frame's vertical post and clamp it with the hand clamp.

Repeat this step down one side of the frame. I found that four (4) clamps per side worked well enough. You may need more, you may need less.

Once you've got them in place, go to the frame's other vertical post and draw the fabric tight and then clamp it in place.

You'll end up with a nicely tensioned backdrop, ready to use for those tricky chroma key sequences.

Up next: conclusion

SPaulovich · May 7, 2005

Part 6: Conclusion

Lighting

To light your green screen, it's best to put a source as close as possible to the front surface - between your actors and the backdrop. That will help eliminate shadows which (trust me again) are a pain to remove later.

If possible, use soft lighting when using a green screen. Bounce your light off foamcore or use a china lantern or other diffuser. It will go a long way toward avoiding the shadows.

Alternate Backdrop

I saved a heck of a lot of money using PVC for the frame. I should have considered alternate backdrops before paying for the one I got. A heavy muslin bed-sheet, already a hideous green color or dyed could have worked, too. Maybe I'll try that as an extension to this tutorial.

Shaw · May 7, 2005

Great stuff

. Thanks for the post!

I'll have to give this a shot! Your screen certainly looks great! Can you describe your lighting setup some more? I'm just curious how you managed to get even lighting with the lights so close to the screen (even given the flourescent lighting).

It would also be of some help (if not just plain interesting) to see some wide shots of the whole setup from various angles.

Great stuff!

clive · May 7, 2005

Very fab and incredibly clear tutorial. Top stuff. :cool:

Any chances of a pdf version?

NicklausLouis · May 7, 2005

Good stuff SPaul.

I'll email my friend the link.

Poke

mdifilm · May 7, 2005

this is great, thanks, where did you get the backdrop from? I have a green screen paper roll ($40) and I just am annoyed by the size and pain in a butt to move it around, I would love to have a backdrop instead

Johnny

cibao · May 7, 2005

Thanks SP...are you going to do a tutorial on the software aspect too??

Chris

SPaulovich · May 7, 2005

Shaw said:
I'm just curious how you managed to get even lighting with the lights so close to the screen (even given the flourescent lighting).

It would also be of some help (if not just plain interesting) to see some wide shots of the whole setup from various angles.

I positioned the screen with a rafter about 1' in front of it. Two fluorescent lights hanging from the rafter gave it pretty even lighting. I also used two standing fluorescent lights on either side as fill lights.

I actually filmed myself making the lights but can't stand the tedious monologue. I'll pull some pictures and make a tutorial like this one.

I'll look around for some pictures, I remember taking a few when I first constructed the frame.

clive said:
Any chances of a pdf version?

Yes, I'll put one together and add a link to the first section.

mdifilm said:
where did you get the backdrop from?

I picked up the backdrop at a show hosted by a local camera/video company. There are some on eBay, I just looked up "green screen backdrop" and a bunch showed up.

Zensteve · May 7, 2005

Awesome article :cool:

mdifilm · May 7, 2005

thanks SP!

Spatula · May 7, 2005

I love you!
Wicked article, DUDE!
Thanks for the contribution! It was very infotaining!

Mikey D · May 8, 2005

Thank you good sir, Mr SPaulovich.
As a younger lego man, I do see why PVC is to become my new best friend.

Mikey D

SPaulovich · May 8, 2005

Here are a couple of shots of the "studio" with the green screen in place.

Note the two free-standing fluorescent lights. Those were used as fill lights to reduce shadows on the screen.

The actor's perspective is a little daunting. It's not an easy task to act when you're looking at this:

Here's the computer setup used for filming.

And finally an obligatory shot of my motorcycle that had to be moved outside for filming...

Spatula · May 8, 2005

Sexy!
Are those director's chairs complete with drink(beer) holders in the armrest???

I want to live in your garage! (with the greenscreen)

SamIAm · May 13, 2005

Probably a stupid question, but would any green sheet work, or would it have to be a certain shade of green? (I know, I know, I'm a complete amateur, but I thought I'd stick my neck out and risk the humiliation)

Shaw · May 13, 2005

Pure green will work the best but any color, so long as the screen is a consistent color across the whole thing, will work fine

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