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zoc
01-09-2006, 11:01 AM
I guyz,
i have to make a movie of a men in bluescreen.
What kind of light and in what position do you think is better to make a easy keylight?
thanks in advanced.

JohnnyRandom
01-10-2006, 06:53 PM
If you happen to be using DV you may consider using green (becuase of 4:1:1 of ntsc dv cams), then deinterlacing the footage in a AE then resaving as uncompressed .avi or image sequence and reimport...

Search google...
Some lighting tips
http://www.digitalproducer.com/2003/12_dec/tutorials/12_22/cw_ckeyphat_tips.htm

simko
01-10-2006, 08:29 PM
Evenly lit blue(green)screen is essential. Dont underestimate this. Don's save on light. Otherwise you might find yourself doing rotoscoping all the time. Possibly lit background and your object with different set of lights.

Consider your shooting gear....DV, HDTV, film. Even footage from HDTV cameras have huge compression applied and it makes it sometimes tricky to pull out a good mask.

Place you object as far from blue(green) background as possible and avoid any shadow casting. Use fill-in light to get rid of or minimize any shadows you might have.

If you not going to track the footage, you may consider to use depth of field and blur out the background a bit (which is easier when object is placed further from background).

Use a good keyer.

beenyweenies
01-10-2006, 10:58 PM
I guyz,
i have to make a movie of a men in bluescreen.
What kind of light and in what position do you think is better to make a easy keylight?
thanks in advanced.

I'm going to assume you're using DV video, so my comments flow from that:

1. As was mentioned, use greenscreen not blue. In layman's terms, DV has more information in the green channel, and fine detail is what you need to key something well.

2. There is a technique called chroma blur that will help you get better results. There are several good plugins that will do this or fake this technique, DVMatte being one of them (http://www.dvgarage.com/prod/prod.php?prod=dvmatteae). You can do it by hand, but that is beyond explaining in one post.

3. For lighting your greenscreen - big, powerful, soft sources of light work better than spotlights because they give more even illumination. The tradeoff is that using these lights will result in more "spill" light on your subject, which brings me to:

4. Subjects should be as far away as possible from the greenscreen, to avoid the green glow (spill) from the greenscreen on your subject and making a good key almost impossible. On professional greenscreen shoots, there is usually about 10-20 feet minimum between the actors and the greenscreen itself.

5. If you are using a camera that has the option, shoot in 24p mode (24 frames per second, progressive frame), as this will be both easier to key than interlaced footage, and give you fewer frames to have to manually tweak when the need arises (it will).


If you are using a DV camera for this project, be warned. Greenscreen using DV is extremely difficult to get right, and is not recommended.

zoc
01-11-2006, 07:35 AM
thanks guys.... now i start with experiment :)

Rickmeister
01-11-2006, 12:53 PM
Some very nice explanations! never figured out an actor should move away from the screen as much as possable... allthough it seems very logical.

Its quite expensive though... need to build the greenscreen larger that way...

evanfotis
01-12-2006, 09:11 AM
Do dvcams (and which) have the option to alter the aperture, just like SLR cameras do in order to get a short/long DOF?

I've used a 3ccd Panny 953 in progressive and the results ( gs evenly lit etc-where ok-nothing more, nothing less)

JohnnyRandom
01-14-2006, 02:06 AM
Do dvcams (and which) have the option to alter the aperture, just like SLR cameras do in order to get a short/long DOF?

My AGDVX100 does a beautiful rack focus.

dbates
01-14-2006, 03:43 AM
Do dvcams (and which) have the option to alter the aperture, just like SLR cameras do in order to get a short/long DOF?

My AGDVX100 does a beautiful rack focus.

Huh? I think I'm missing something here. I know what DOF is, and I know what a rack focus is, and they are not at all similar.

To answer your question, evanfotis, I don't think so. Interchangeable lenses give you some amount of aperture control, but it's not on-the-fly like SLR lenses are (afaik).

Rickmeister
01-14-2006, 10:13 AM
Huh? I think I'm missing something here. I know what DOF is, and I know what a rack focus is, and they are not at all similar.

To answer your question, evanfotis, I don't think so. Interchangeable lenses give you some amount of aperture control, but it's not on-the-fly like SLR lenses are (afaik).

there are adapters on the market for camcorder so you can connect a different lens (like a SLR lens) for beter DOF. http://www.redrockmicro.com is one of them.

JohnnyRandom
01-14-2006, 05:28 PM
Huh? I think I'm missing something here. I know what DOF is, and I know what a rack focus is, and they are not at all similar.


So when you use rack focus the foreground is in focus and the background is out of focus and then focus is adjusted to recieve the opposite effect, correct? So what happens with DOF object in focus everthing else blurred correct? So how are they not similiar?

dbates
01-14-2006, 06:47 PM
So when you use rack focus the foreground is in focus and the background is out of focus and then focus is adjusted to recieve the opposite effect, correct? So what happens with DOF object in focus everthing else blurred correct? So how are they not similiar?

A rack focus is a change in focus while the camera is shooting. For example, sometimes the camera focuses on something in the immediate foreground (grass, leaves, etc) and then shifts focus to the actors. In contrast, depth of field refers to the area in front of and behind the plane of focus, that is still in sharp focus. A shallow DOF produces a very blurred background (macro shots, for instance), whereas a deep DOF keeps most of the image in sharp focus.

Basically, a rack focus is a change in focus. DOF is the amount of area that is in focus.

--dbates

JohnnyRandom
01-14-2006, 07:26 PM
I see what you are saying.

So if there were no DOF then everything would be in focus, therefore you could could not do a rack focus, right? Do you understand what I am getting at? So is there no effect of DOF when you do a rack focus?

beenyweenies
01-14-2006, 07:42 PM
Huh? I think I'm missing something here. I know what DOF is, and I know what a rack focus is, and they are not at all similar.

To answer your question, evanfotis, I don't think so. Interchangeable lenses give you some amount of aperture control, but it's not on-the-fly like SLR lenses are (afaik).

My experience has always been that most cameras with a fixed zoom lens have poor DOF, meaning it can't throw things out of focus easily. To clear that issue up, here's what depth of field really is. When you focus on a subject (say, 10' from the camera) there isn't just a tiny sliver of the subject in focus, there is a whole space that is in focus that can be anywhere from 3' to infinity deep. This is known as the depth of field, or how "deep" the in-focus range is. Through proper settings you can limit this depth of field to be something like 3' deep, meaning anything outside of that 3' space will be out of focus. You adjust where that 3' space is in relation to the camera by focusing - this is merely moving the lens element in and out, and in the process shifting the area of focus closer and further from the camera. But as you focus, the amount of space that will be in focus remains fixed because it is derived from settings that have nothing to do with the focus knob on your camera. This space which is "in focus" isn't centered on the subject, by the way, it is actually more like 1/3 in front of the subject and 2/3 behind the subject. So if your settings would give you 3' of usable focus, 1' would be in front of the subject and 2' would be behind the subject. More on that later...

Shallow Dept of Field is the product of the lens element being close to the CCD, and the iris being opened up as wide as possible.
Most prosumer fixed-lens cameras, including the DVX100a (which I own), try to cover all your potential needs, so they use a zoom lens that can't go very wide angle, doesn't zoom in very close, and the iris won't go as wide as a pro lens. This is important because the distance the lens element is to the actual CCD and the aperature setting used are forever tied together when it comes to depth of field. A short lens (wide angle) can give the best depth of field because the lens element is much closer to the CCD. Conversely, if the iris is closed way down because the scene is brightly lit, this will give greater depth of field (i.e. not shallow).

In short, the two ways to get shallow depth of field are:
1. Use a wide angle lens with as wide an iris setting as possible OR
2. Get far away, zoom in and open the iris full bore. Your background will have to be pretty far from the subject for this technique to work, however.

As mentioned before, the depth of field reaches about 1/3 in front of and 2/3 behind your subject, so another way to get shallower depth of field is to focus properly on the subject but then adjust the focus to be slightly in front of the subject so that it pulls the depth of field toward the camera as well, effectively moving the 2/3 focus range behind the subject closer in. This allows you to have the background slightly closer to the subject and still be out of focus. Confused yet? Me too.

By the way, those lens adapters mentioned on this thread that allow you to put other lenses on are usually crap - they introduce distortion and poor optics all around, and you are still slapping it on the front of a consumer grade zoom lens.

Rickmeister
01-15-2006, 01:24 PM
By the way, those lens adapters mentioned on this thread that allow you to put other lenses on are usually crap - they introduce distortion and poor optics all around, and you are still slapping it on the front of a consumer grade zoom lens.

Most of them are crap... massive amount of light loss... flickering and ghosting...
redrockmicro doesnt have these problems... its a simple and relative cheap way to get some more quality out of your prosumer camcorder...

beenyweenies
01-17-2006, 05:30 AM
Most of them are crap... massive amount of light loss... flickering and ghosting...
redrockmicro doesnt have these problems... its a simple and relative cheap way to get some more quality out of your prosumer camcorder...

Yeah those are pretty sweet... But most mini35 gear being $10k plus, it's a little out of reach for most. I'd love to get one of those myself, but instead I'm saving for an HVX200.

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