HDCAM keying

[rose]

hello all

does anyone have any experience keying HDCAM?
can you tell me what the specific problems are with it ?

anyone?

; )

[guillem ramisa]

junglerose wrote:

hello all

does anyone have any experience keying HDCAM?
can you tell me what the specific problems are with it ?

anyone?

; )

Compression sucks. You’ll get similar problems as when you key dv footage. Use the same the techniques to get rid of it (search this forum for keying DV). Avoid hdcam bluescreen if you can.

[Alain Lacroix]

thanks for replying

could you be more specific?
e.g. are there some movements/patterns/contrasts etc. that cause more problems than others?
what are the artefacting problems?
i have heard there are random artefacts (invisible on still frame, only visible in playback, making keying impossible) : is this true?

need to have more information so i can discuss with the producer, director and dp: specifics are great

; )

[bnw]

First problem: the chroma subsampling, which means you need to blur the chroma to avoid stair-steps, which means your key will always be somewhat soft, lacking in detail. Ideas to help with this: don’t try and key complex edges, or try and get a good amount of luma contrast on the edge to help the keyer – if you must key hair or convoluted shapes, try and get some brightness difference between the screen and the FG. Yeah, this will cause problems with spill if you take the screen brighter and the FG darker, especially if it’s blonde hair. The other way might be worth a try, a slightly dark screen. If you’re going to do that you’ll probably want to key with something which doesn’t use the colour-difference method, because they like their screens to be very primary colour. Try maybe Primatte or Flame’s keyers rather than Ultimatte or Keylight. But still don’t go too dark or you’ll lose the chroma difference and end up just luma keying 😉

And then the compression artifacts… I’m not sure what you do about those to be honest, other than roto 😉 As always I guess try and get the screen a similar brightness to your background, so you can despill and not have obvious luma differences… which of course probably means you can’t try the stuff above.

Good luck, just ideas 🙂 Let us know what you figure out!

[guillem ramisa]

junglerose wrote:

thanks for replying

could you be more specific?
e.g. are there some movements/patterns/contrasts etc. that cause more problems than others?
what are the artefacting problems?
i have heard there are random artefacts (invisible on still frame, only visible in playback, making keying impossible) : is this true?

need to have more information so i can discuss with the producer, director and dp: specifics are great

; )

The dangerous thing with HDCam, HDV (and other compressed formats) is that for persons like directors, DOPs or producers (that want to cut budgets) the material at a first glance – if it’s well shot – might look really good. But, and it is a big but, as soon as you need to do any major changes the material will reveal it’s real nature… nasty digital, blocky, ugly looking artifacts due to the compression of the chroma channel. So a blue/greenscreen might look perfect at a first glance but to get a decent key will be nearly impossible without workarounds like bluring your chroma channel bla bla. Avoid shooting fine detail like hair and such. And as always it’s important to have you’re material well lit and exposed but it is even more so in this case cause if luminance is fu**ed then you have nothing. But as you probably already guessed the result will never be perfect. So for effects work try and save money somewhere else.
I don’t know what your production will look like. You say you’ll need to key your footage. If you mean that you’ll need to shoot bluescreen but only a few shots maybe you can shoot that on film and then the rest can go digital?
If you need to go HDCam anyways I can only say I’m sorry and that I feel for you. And tell the director he won’t get any award winning effects this way. He might change his mind 😀 Cheers.

[Scott]

Don’t be too afraid junglerose. It will likely be more difficult because of the compression, but it can be done. I finished a feature shot on HDCAM last year, and had 15+ green screen shots. This stuff was well lit, but the subject was a yellow plane with a highly reflective surface… against a GREEN screen. Not easy.

I recommend isolating multiple areas of the shot to pull separate keys. The compression pulls a lot of the detail out of the color. Isolating areas allowed me to pull more precise keys. Can be a big pain, but it’s better than roto.

md

[Alain Lacroix]

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Don’t be too afraid junglerose. It will likely be more difficult because of the compression, but it can be done. I finished a feature shot on HDCAM last year, and had 15+ green screen shots. This stuff was well lit, but the subject was a yellow plane with a highly reflective surface… against a GREEN screen. Not easy.

I recommend isolating multiple areas of the shot to pull separate keys. The compression pulls a lot of the detail out of the color. Isolating areas allowed me to pull more precise keys. Can be a big pain, but it’s better than roto.

md

---

hmmmmm thats interesting: thanks md: could you average a guess at extra time in comping these shots compared to say film? 50% extra time? less? more? i know its difficult, but i want to get an idea of what i’m in for if they go this way. this is strictly a budget issue: i have worked mostly on film, which was a dream… but i dont think this is an option.
just need to get my head around what i’m actually considering work-wise in the schedule and plan accordingly. estimations would help with that.
; )

[Andrew Pellicer]

If acquisition format is still being decided upon, it may be worth it to look into the panasonic stuff if 1080 res isnt absolutely needed. DVCPROHD is 4:2:2 and much easier to pull a key on in general, and if shot well, nice lenses, etc etc, panasonic 720P uprez to 1080 still looks extremely nice. I hear tons of people say the same thing in reference to pana HD, “The only reason I would shoot sony instead of panasonic is if I ABSOLUTELY need 1080.”

No, i’m no pana fan! 🙄

have fun,
adam

[Author]

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