Greenscreen example

Hey, no apologies necessary, this is a great forum with great forum members. I could understand how you could read my questions that way. That's one problem with things being written in forums (and emails for that matter). I looked at some of your previous posts, and you are in a similar situation that I am in two ways. First, it looks like you are looking for a good HD/HDV solution - and the best camera for your money. Second, you're a Mac G5 user.

I had planned on purchasing a ReflecMedia studio set up for a few ideas I had, but postponed that to divert the money to towards a HD/HDV camera. I will be doing some greenscreen work, but I don't know how much. If I had to break it down into a percentage, it would probably only be about 25%.

I'll just have to continue to weigh the pro's & con's of the current camera's along with all the various ways it will be used (from greenscreen to mounting it in a car) and make my decisions from there. I appreciate the info you supplied. I'm sure I'll see you around since we have some common interests.

[Rob McCardle]

"Rob,
We are discussing keying, which doesn't seem to be done in the field too much! ;-)"

Rotflmao - errr, yeah you got a point there.

Sorry - I'm looking at them all from the angle of what's going to be most useful/general purpose cam.

[Jerry Mohn]

http://www.lafcpug.org/Tutorials/bas...age_soltz.html
http://www.barefeats.com/
http://homepage.mac.com/comeback/iblog/Work/B787268209/
http://www.blackmagic-design.com/products/sd/

these are a few links to get you headed in the right direction. I have been looking into this option as well.

Under $3000 for the raid (8 x sataII 500g) plus box not including the card($300) and decklink($600)

Raids come in all different flavors, the SATA raid has quickly developed into a low cost option for editing uncompressed 8bit HD, the jury is still out on 10bit HD but technically it is getting possible.

I am waiting for a few more months until I get closer to the due date of my project because the technology is advancing fast, specifically the raid cards.
You would need the latest mac loaded with ram and FCP, that is what I am using so that cost could range from $4000 to $10,000 depending on what you wanted.

[Riley Harmon]

i was able to pull a key from this in keylight nicely, better than dv. With just a few tweaks, I got a good key. Normally with DV it took LOTS of tweaking.
http://rileyharmon.com/temp/comp.tif

[Craig Seeman]

Green in the field.
I've been doing that since 1990. Shooting corporate video with an exec in their office. Bring it back home and key in the appropriate marketing material in back.

Moving video.
You simply can't change the quality of a key from a still frame. All sorts of problems can expose themselves when you play back a key that you won't see in a still frame. I'd love to see a link to such a demo.

Codec can be an issue.
My eyes see softening on fast action with HDV codec. Try shooting a bouncing basketball in front of a green screen using HDV vs DVCProHD for example (maybe a bicycle tire with spokes spinning). For corporate video how about shooting a fast moving piece of machinery in front of a green screen. Yes to can upsample HDV to DVProHD (or uncompressed) but HDV may have already done it's damage to a fast moving subject.

I would love to see HVX source video (moving subject if possible) shot in front of green screen so I can try keying myself.

[Stephen L. Noe]

Originally Posted by Craig Seeman

My eyes see softening on fast action with HDV codec. Try shooting a bouncing basketball in front of a green screen using HDV vs DVCProHD for example (maybe a bicycle tire with spokes spinning). For corporate video how about shooting a fast moving piece of machinery in front of a green screen. Yes to can upsample HDV to DVProHD (or uncompressed) but HDV may have already done it's damage to a fast moving subject.

I would love to see HVX source video (moving subject if possible) shot in front of green screen so I can try keying myself.

I'd like to see the DVCPro50 greenscreen from an HVX as well.

Just by chance, have you tried to key a 480p60 HDV clip sourced from the HD-100?

[Joseph H. Moore]

Green in the field.
I've been doing that since 1990. Shooting corporate video with an exec in their office. Bring it back home and key in the appropriate marketing material in back.

Point taken. My head is always in the narrative film world and it's easy to forget the other side. ;-)

[Alister Chapman]

In theory at least, well lit green screen should be MPEG2 and hence HDV friendly as large parts of the image never change and contain little detail so the codec dosn't have to work too hard. However the 4:2:0 subsampling isn't good. It may be that if you use a good intermediary that resamples at 4:2:2 and does some chroma restoration, such as Cineform, you could get a half decent key. Need to try this out to see.

[Joseph H. Moore]

Alister,
I agree. The codec isn't much of a factor here. It's the subsampling that can be killer. That's why I'd give the nod to the H1's SDI output.

[Alister Chapman]

If you compare the raw green screen image and the final composite you can see that the key cut-out has been shrunk to mask any keying artifacts, there are also background rocks visible through the left side of the guys face by his eye. Trying to key hair like that is a nightmare with any setup, but if you compare the clean image and the composite you will see large amounts of hair is completely missing. Shrinking the key matt by a few pixels is a good (and often used) way of hiding a less than perfect key and this has clearly been done with this image.

Still the final result looks good although the background is somewhat sharper then the foreground.

My own experiments with the foregound image have shown that it keys reasonably well, but would take a lot of work and a fair bit of fiddling to get a final result as good as the one posted. I would love to see the image moving as that would really show how much the matt has been shrunk and what is really going on with the hair.

[Craig Seeman]

Joseph,
Just to be clear, SDI out of the H1 gets it out of the camera and into a better codec than the HDV that would damage it. That's obvious. Unfortunately most shoots with a $6-$9,000 camera in the field won't have the budget to handle SDI on location (for me at least). Studio shoots are another story but most of my shoots are in the field and lugging the equipment or possible extra crew for SDI is not practical. Heck, if the budget were that high one might start to look at 2/3" cameras, at least as a rental, for shoots that also budget for an SDI video path on location.

HDV compession may simply make a green screen key problematic if the object in front of the screen has significant motion. Going into 4:2:2 or even 4:4:4 color space can't improve the softening if you're coming from the file already recorded in HDV on tape.

I want to shoot a decent green screen in an exec's office and I want to be able to shoot fast moving products, whether a tennis racket in motion or a piece of high tech manufacturing gear without the image softening if it's going to a portable record medium.

[Joseph H. Moore]

All things being equal I'd like the bitrate of DVCPRO, but alas, all things are not equal, and I'd rather key a sharp HDV shot than a soft DVCPRO shot.

So far, the images from both the H1 and the HD100 are showing very little MPEG artifacting ... far less than expected.

I haven't seen a green screen shot from the H1 yet, but I wouldn't dismiss it sight unseen simply because you think HDV "should" perform worse.

[Jason Varner]

I was just wondering....which format would be better for pulling a cleaner key, progressive or interlaced. Thanks.

[Steev Dinkins]

Originally Posted by Jason Varner

I was just wondering....which format would be better for pulling a cleaner key, progressive or interlaced. Thanks.

Progressive rules, big time. Interlaced video is a nightmare for post process work such as keying, rotoscoping, masking, compositing, and speed manipulation.

[Alister Chapman]

Converting from HDV's 4:2:0 colour space to 4:2:2 can and does significantly improve both final image quality and keying if done correctly. Normal playback of HDV simply creates a 4:2:0 colour space image, however if the codec or conversion to 4:2:2 process is smart it can fill in much of the missing data. Admittedly the codec is "guessing" as to what should be there but if on one sample you have green, then at the next sample you have is green then it is probably safe to say that the missing sample in between is green. Due to limitations of lenses and optics you will almost never see a pixel to pixel change from say red to green, there are likely to be several shades in between so well executed sub sampling and conversion can work very well.

I use the cineform codec a lot and it really does clean up the chroma removing many of the 4:2:0 colour space artifacts.

Besides which there are new keying algorithyms and vector based keying which work very well with both 4:2:0 and 4:2:2. Most modern keys are not derived just from the chroma information, luma is also very important to getting a good key. But if the image is soft, it will always be soft. The sample being looked at here looks soft, the final composited image does not look right, yes it might look clean (apart from all the cropping) but the foreground is soooo much softer than the background, maybe it's out of focus?