Green screen frame ???

maureeno · #1 06-10-2006, 05:12 PM

Has anyone built a green screen frame? If so, what did you use?

I'd like to build one and alligator clamp on the backgrounds for photo shoots, mainly a green screen that would make it easier for the magic wand eraser to operate.

It seems far more cost effective to construct one's own frame than to purchase the entire outfit.

Maureen

fpellerin · #2 06-10-2006, 09:33 PM

Funny you should mention this...I'm intend to build one too! I've got no definite plans yet, but to form the frame I'm thinking of using metal pipes which would screw into 90 degree fittings. That way, I could easily take it appart and store it when it's not in use. I'll post pictures of the thing once I get it set-up (this month I hope!)

Cameraken · #3 06-11-2006, 07:40 AM

Hi Maureen.

It sounds like you want to make a ChromaKey Background

http://www.coloramaphotodisplay.co.uk/bck_chromakey.asp

It is important that these are evenly lit or they don’t work well, so holding the background flat is quite important.

There are special supports to hold these.
http://www.coloramaphotodisplay.co.uk/suppIndex.asp

But they are quite expensive.
They can be fastened to a wall to keep them flat, however if you wish to make a movable one, I would suggest you take a look in your local plumbers merchants. You can buy 2” plastic water pipe in long lengths and push fit ‘T’s and Angled fittings which can easily be fitted together to make a solid frame.

I found a tutorial here

http://homepage.mac.com/geerlingguy/...eenscreen.html

They are using ¾” pipe. If you are making a big frame you may find 2” more substantial.

Hope this helps

Ken.

Mike · #4 06-11-2006, 08:37 AM

If you are going to use rolls of paper, then I would look into one of those roller devices and hang it either on the wall or the ceiling. That way the background can just be rolled down when you need it and rolled back up later. Setting up some kind of holder each time you want to use the background is a real pain in the a**!

I have been in home studios where the roller device had a kind of box like structure built around it that did a good job of hiding it when not in use. It kind of looked like some kind of structual beam across one end of the room.

In my studio I built a frame like structure that will hold up 3 rolls of paper, plus whatever else I want to hang on it, and the whole thing has wheels under it so I can roll it around.

maureeno · #5 06-11-2006, 12:56 PM

Quote:

Originally Posted by Cameraken

Hi Maureen.

It sounds like you want to make a ChromaKey Background

http://www.coloramaphotodisplay.co.uk/bck_chromakey.asp

It is important that these are evenly lit or they don’t work well, so holding the background flat is quite important.

There are special supports to hold these.
http://www.coloramaphotodisplay.co.uk/suppIndex.asp

But they are quite expensive.
They can be fastened to a wall to keep them flat, however if you wish to make a movable one, I would suggest you take a look in your local plumbers merchants. You can buy 2” plastic water pipe in long lengths and push fit ‘T’s and Angled fittings which can easily be fitted together to make a solid frame.

I found a tutorial here

http://homepage.mac.com/geerlingguy/...eenscreen.html

They are using ¾” pipe. If you are making a big frame you may find 2” more substantial.

Hope this helps

Ken.

Ken, that's what I was thinking about. I was even wondering if I could pop into some jumble sales or shops and see if they have any old home movie projector screens there.

Thanks!

Maureen

cspringer · #6 06-11-2006, 01:56 PM

I would use White or Black for photos. Most threads I've read talk about the color cast caused by blue/green screens which work better for movies.

Cameraken · #7 06-11-2006, 02:28 PM

The reason for using Chromablue and ChromaGreen backgrounds.

These colours were specifically chosen because they are two colours which do not occur very often in everyday life. This means that software can extract this colour without extracting any colours in the subject. This is especially important in video where there may be thousands of frames to extract.

This is less important to Photoshop users who just need to make a single mask. However getting good separation between the subject and the background makes extraction easy.

The common problem is that subjects are stood too close to the background and the background colour is reflected back onto the subject which totals defeats the object.

So, yes, any colour may be used as long as it is sufficiently different from the subject. This is especially true for hair which is the hardest to extract.

Just make sure the background is lit evenly and then extraction is very easy.

A projection screen would be fine. But the biggest you are likely to find ‘cheap’ is about 4ft square.

Ken.

maureeno · #8 06-12-2006, 12:49 AM

Quote:

Originally Posted by Cameraken

The reason for using Chromablue and ChromaGreen backgrounds.

These colours were specifically chosen because they are two colours which do not occur very often in everyday life. This means that software can extract this colour without extracting any colours in the subject. This is especially important in video where there may be thousands of frames to extract.

This is less important to Photoshop users who just need to make a single mask. However getting good separation between the subject and the background makes extraction easy.

The common problem is that subjects are stood too close to the background and the background colour is reflected back onto the subject which totals defeats the object.

So, yes, any colour may be used as long as it is sufficiently different from the subject. This is especially true for hair which is the hardest to extract.

Just make sure the background is lit evenly and then extraction is very easy.

A projection screen would be fine. But the biggest you are likely to find ‘cheap’ is about 4ft square.

Ken.

You're absolutely right, Ken, about the colours and the extractions for which I'd be using the green screen. I've laid plans to utilise a brisk wind fan, as well, and the green screen would come off cracking good in my view in being able to extract and leave the hair fairly well natural.

You've a brilliant point about the screen lighting, as well. I'll need keep a close eye on that detail.

Thanks!

Maureen

RokcetScientist · #9 06-12-2006, 05:37 AM

As these 2 colors, green and blue, were specially selected for Chromakey, what is the difference between them? When would you use the one, and when the other?

And are there precise RGB and/or CMYK codes for those specific two colors?
Because if I could recreate them with a printer I would have ChromaKey capability for macro shots! That could be interesting to experiment with! I see a whole realm of possibilities opening up...

Cameraken · #10 06-12-2006, 12:50 PM

Quote:

Originally Posted by RokcetScientist

As these 2 colors, green and blue, were specially selected for Chromakey, what is the difference between them? When would you use the one, and when the other?

The exact colour is not important to Photoshop users (It may be different for some video applications)

A mask can be made easily from any colour as long as it is different from the subject. So if you were photographing a black and white cat then red, blue, green, yellow or any colour except black or white would work just as well.

I will answer your other question in your other thread.
http://www.retouchpro.com/forums/showthread.php?t=13773

Ken.

cspringer · #11 06-12-2006, 01:29 PM

Quote:

Originally Posted by maureeno

You're absolutely right, Ken, about the colours and the extractions for which I'd be using the green screen. I've laid plans to utilise a brisk wind fan, as well, and the green screen would come off cracking good in my view in being able to extract and leave the hair fairly well natural.

You've a brilliant point about the screen lighting, as well. I'll need keep a close eye on that detail.

Thanks!

Maureen

Talking from my masking hair experience...the hair gets a green cast on the ends and doesn't work. If you are talking about solid objects it doesn't matter but whispy hair is another game. If someone has a fix I could you please post because people keep sending me green screen pics and what normally takes a couple of minutes takes much longer.

maureeno · #12 06-12-2006, 01:45 PM

Quote:

Originally Posted by cspringer

Talking from my masking hair experience...the hair gets a green cast on the ends and doesn't work. If you are talking about solid objects it doesn't matter but whispy hair is another game. If someone has a fix I could you please post because people keep sending me green screen pics and what normally takes a couple of minutes takes much longer.

Whoa, you're correct, aren't you, about the green cast to the hair wisps!

Would white work any better do you think?

Maureen

Mike · #13 06-12-2006, 03:19 PM

Quote:

Originally Posted by maureeno

Would white work any better do you think?

Maureen

If you use white with a person, then the white part of the eyes and some of the teeth will go away with the background!

Mike · #14 06-12-2006, 03:23 PM

Quote:

Originally Posted by cspringer

Talking from my masking hair experience...the hair gets a green cast on the ends and doesn't work. If you are talking about solid objects it doesn't matter but whispy hair is another game. If someone has a fix I could you please post because people keep sending me green screen pics and what normally takes a couple of minutes takes much longer.

What are you pasting your extracted image onto? That will make a difference.

Also it sounds like maybe the shooters are not doing it quite right. One needs to have that hair a good distance from the green background (like 6 feet or more). Also the background cannot be to bright (or too dark) and of course has to be even.