Getting Best results from Blue Screen and Mattes?

Gra · Post by **Gra** » Wed May 17, 2006 9:01 am

Hi Guys

Has anyone any tutorials for Green screen/ matte work for MSP8?

Now I know I've a pretty lower-end market camcorder and I know that's a big part of the problem, but I'm trying to do a segment in front of a green screen and the finished results are a bit fuzzy around the edges.

I've followed Nick's tutorials on Justhome (and downloaded his filters), which are designed to compensate the problems of lower end market camcorders but the results do not come anywhere near those suggested. It could be because his tutorials were written for MSP7 (and maybe I've got the sequence wrong in trying to transfer to MSP 8, where overlay tracks are the other way around).

Any tips or advice would be very welcome.

Gorf · Post by **Gorf** » Wed May 17, 2006 9:53 am

Stand your subject as far from the screen as possible - as long as their outline is bounded by the screen area, you should be OK. The purpose of the screen is to key their outline, not fill the shot, so you can manually mask out bits of wall etc that might be in shot behind the greenscreen.

The reason you stand them so far away is to reduce reflected green tint on the subject.

Use an actor with flat hair. Make sure their clothes don't have any of the screen's colour in them. Don't use any old green fabric or paint - get a sample from a company that makes chromakey paint, then take it to Homebase (or your US equivalent)

Try to match lighting. If your background clip will be outdoors on a sunny day, take your actor and the greenscreen out on a sunny day. Try to match shadows.

There's a greenscreen clip provided with MSP8.

Gra · Post by **Gra** » Wed May 17, 2006 10:21 am

Thanks Gorf, I did build in some of those tips when I was filming (as I mentioned, the camcorder is a bit cheap and I did my best to give myself a chance) but the problem is a fuzzy jagged edge mainly around a dark grey jacket, which I'm trying to key out in post production.

Devil · Post by **Devil** » Wed May 17, 2006 11:01 am

What format and colour space does your cam work in? This can make a big difference as to how best to proceed.

Gra · Post by **Gra** » Wed May 17, 2006 8:54 pm

Thanks D.

According to the cameras specs, the system is Mini DV, SD format;
Television system CCIR: 625 lines, 50Fields, PAL Colour signal;
PCM digital recording16 bit & 12 bit;
Video compression is MPEG 4.
(I'm not sure what is meant by colour space unless you mean PAL colour.)

Does that offer any clues?

sjj1805 · Post by **sjj1805** » Wed May 17, 2006 11:27 pm

Another thing to mention here is Blue screen -v- Green Screen.
You gave the post one title then in the subject mentioned the other so clearly like me you were not quite sure of the difference between the two.
That is not sure until I read the excellent underpriced book by Charlie Hills

"Getting Results with Media Studio Pro 8"

Put simply green screen gets rid of background colour that is more or less specific to a certain shade.

Blue screen does a similar job but gets rid of a range of similar colours - in otherwords it is less specific.

BernardD · Post by **BernardD** » Thu May 18, 2006 4:51 am

DELETED

Gra · Post by **Gra** » Thu May 18, 2006 7:28 am

Hi Steve
Thanks for that. I've done a bit of surfing over recent months and the Blue vs Green screen debate is quite interesting with lots of views either way from around the world and no real conclusion in the middle.

I think I'm going to invest in Charlie's book as so many experienced users say how good it is but I can't decide at the moment whether to go for the hard copy or just the PDF download.

Gorf · Post by **Gorf** » Thu May 18, 2006 8:40 am

If you're unsure which to go for - go for the hardcopy.

I got the download on the basis that it would cost more to send a harcopy here than to get the PDF printed here. I was wrong...

Devil · Post by **Devil** » Thu May 18, 2006 9:09 am

Your DV (DV25) system has a colour space of 4:2:0 co-sited. This means that every other pixel on odd-numbered lines in each field carry the Cr signal and the even lines carry the Cb signal.

This is reasonably good for green screening, slightly less so for blue screening. Howver, 4:2:2 co-sited, as used for the DV50 and DV100 (pro) video as every other pixel on every line would carry both the Cb and Cr components.

Your MPEG-4 also has 4:2:0 colour space but the Cb and Cr colour samples are calculated, averaging 4 pixels in each field, weighted towards the first pixel of the group of 4. This means that even lines in each field are displayed with the same colours as the odd lines; if, in reality, the colours are different between the odd and the even line, none of the colours on either of these lines is correct. For this reason, colour-screening is not as good and fringeing can occur.

You have not made it very clear. Do you edit in DV AVI and then transfer to MPEG-4 or do you edit in MPEG-4? If the latter, it is definitely not going to give you the best results. Always edit in DV AVI, render and only then encode to MPEG-4 (also applies to all types of mpeg).

Post by **Ron P.** » Thu May 18, 2006 11:09 am

Gorf wrote:If you're unsure which to go for - go for the hardcopy.

I got the download on the basis that it would cost more to send a harcopy here than to get the PDF printed here. I was wrong...

You might check with Charlie Hill, I think I remember reading that if you wanted the hardcopy and purchased the download copy, he will only charge you the difference in price between them...

Ron P.

hillsc · Post by **hillsc** » Thu May 18, 2006 2:38 pm

That is true: you can download and if you change your mind later, the hardcopy purchase is the difference. You don't have to buy it twice.

Gra · Post by **Gra** » Thu May 18, 2006 4:35 pm

Thanks for all the replies.

First, many thanks Charlie for clarifying the purchase situation. I'll go on to download and I'm sure others following this thread will find it useful to know about only paying the difference if they are unsure what is the best option first.

Devil, thank you for your info. It's really helpful. At the moment, I capture from the camcorder using DV Type 1 and edit in DV type 1 (AVI) as well and output my finished material to either AVI (to view on my PC) or MPEG 2 (when I'm going to put it on DVD).

I do not have the MPEG 4 option as I have not downloaded the MPEG 4 update pack. Would it be best to do so and output to MPEG 4 for compatibility and best quality? I ask this as final outputs are not as sharp as I'd like but so far have put that down to camcorder capture capability.

sjj1805 · Post by **sjj1805** » Thu May 18, 2006 5:39 pm

Gra
The tutorial I am currently working on - although I am using VideoStudio 9/10 as the software, contains information concerning the different formats and although the article is far from finished should answer your query.

http://phpbb.ulead.com.tw/EN/viewtopic.php?t=13421

Gra · Post by **Gra** » Thu May 18, 2006 6:04 pm

Hi Steve

Thanks for the link to the tutorial you are building and for your efforts to help the likes of me. It is brilliantly clear and nicely laid out. I'm sure it will be very helpful to those of us still learning the basics trying to grasp some of the basic technical nuances.