Another Chroma Key Problem

[Chris Wright]

google these keywords and you’ll learn a heck of a lot about green-screening.
“the specialist green screen”

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“If the blur comes from a too slow shutter speed or by too narrow depth-of-field, you’ll have to tweak the keyer and possible sacrifice other parts just to manage the fuzzy edges.

A blurred edge between foreground and background means that you will have to compromise between the edge and despilling settings, and quite possibly have to keyframe these settings to compensate for different levels of blur on different parts of the clip.

Instead, add motion blur in post by using optical flow technologies such as ReelSmart Motion Blur and add depth-of-field by layering chroma clips and post-blurring them.”(the specialist)
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its impossible to answer your lighting, spill, and shadow problems precisely without seeing a high quality photo of the original shot, but I’ll tell you this, I’d rather face horrible green spill problems than slow shutters. Also, try a demo of Primatte Keyer Pro. It’s a little more intuitive with mouse clicks and transparencies.

[Tom Scott]

Try using a faster shutter speed. You might have to increase your lighting a little to compensate.

[Blahtor Magnus]

I am a newbie.
Shutter speed in video shooting would mean frames per second?

I am shooting at 30fps but I have the option of shooting at 60 fps.
Will moving from 30 fps to 60 fps require exactly two times more light?

[Blahtor Magnus]

Thanks, I think I almost got it, hehe.

I read a post on a forum and it was about my Crappy camera’s waker brother: Aiptek A-HD (I’m using Aiptek A-HD+ – pretty much the same thing and just as crappy but has the ability to shoot in close to Full HD resolutin).

Here goes the post from some guy:

“I discovered the reason the Aiptek handheld video footage makes everyone look like they have Parkinsons.

It is beacuse the iris is always f/2.8.

Since the iris doesn’t open or close the only way to vary the exposer of the frame is through THE SHUTTER SPEED.

In low light at 30fps you get a natural blur. But in bright sunlight the Shutter speed is raised.
So at shutters at 1/100th or so a sec the picture is sharp. You are getting a min-no blur in the video scene so it looks choppy. Kinda like the old “sports Mode” of last gen camcorders. pause your jerky footage. Each frame is pretty sharp.

I’ve tested this by shooting in overcast and all the video has the pleasant blur we all associate with 24-30 fps video.

So in sunlight you need to cut down the amount of light. Neutral Density filters should do the trick, I think. With less light the shutter speed drops.

If your into photography just remember the the Aipteks use SHUTTER priority, not Aperture.”

Being a pretty lame newbie and someone whose English sucks, I’m not quite sure I understood alll of what is being said by this guy (especially in the part where he says that Aipteks use Shutter priority and not Aperture), but what I got is that I need more light to raise the shutter speed of the camera.

The problem seems to be that when you have more light and a faster shutter speed, every frame is sharp and nice and this creates some shaking problem because of the lack of any motion blur.
Hmmmm… GREAT!

I think I could use this “problen” for my advantage in green screening. If more light will make every frame sharp and blur-less, then I guess this is what I need – will help me get blurless footage that keys out nicely.

The only problem left is to figure out how to place more lights in the room…
I have no space to place lights on the sides of the green screen, so I placed two 500 Watt lights infront of it and pointed them at the ceiling. This setup gets me nice, shadowless diffuse light.

But seems that my present lighting rig is too weak to raise the shutter speed of the camera.
Maybe adding two more 500W lights will solve the problem.

_

[Brendan Coots]

I pointed this potential danger out to you in your previous keying thread, you shoulda listened to me. As I said then, shoot the highest frame rate you can when keying.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[Blahtor Magnus]

My camera’s highest framerate is 60 frames per second.
I made a couple of test videos at 60 fps and it didn’t help with the motion blur at all.
The only thing that seems to help a bit is to add more light to the scene. And this is a real problem in my case since I don’t have space.

I will experiment with adding a huge white sheet in the background because the white balance of this camera (which can’t be adjusted manually) sucks beyond suckdom and it keeps changing the colors from footage to footage even with the same lighting setup.
This causes all kinds of problems and more often than not results in dark foreground objects on an overxposed green screen and blurry movements.

[Brendan Coots]

I did see after writing my post that your camera does some really strange stuff regarding sharpness so sorry for the tone of my note. It sounds like your camera does 30p or 60i (29.97 interlaced) which should be sufficient to help with motion blur, but it’s doing whatever it wants based on your lighting, which is just lame. Your camera is obviously holding you back because it lacks manual settings.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[Blahtor Magnus]

I totally agree. The camera is really bad.
I bought it because it was HD.
Seems that it’s not useful for anything else but taping your kid’s first day at school or something.