Z1 & Chroma Key

[Gareth Watkins]

Hi there

I've run several searches through the board on Chroma Key set up, which have given me all the basic info.
However I've a couple of queries about using the Z1 for this technique. I shall be out putting to SD for a DVD.

Which is the best setting to use to make the keying easier? I often shoot CF25 for SD useage and get good results. Would it be a good idea to use this for green screening? or shoot 50i and then deinterlace with say Virtual dub?

Also would it be better to turn the sharpness down to say 6 or 7 to help avoid green spill? I usually set it at 10 or 11. I intend to light the background separatelyt and backlight my subject.

Finally would using a filter like say a Black Mist or Pro mist help or hinder the technique?
Thanks for any advice on setting up the Z1.
Cheers
Gareth

[James Huenergardt]

Hi,

You probably won't want to use any CF modes on the Z1U when shooting on a greenscreen. It halves the resolution (see ww.adamwilt.com/HDV/cineframe.html)

Deinterlacing might work fine. I've tried it both ways with Cineform in After Effects and didn't notice much if any difference.

You won't want to use any filters either.

I usually capture in HDV and key in HDV then downrez in After Effects to SD.

The best thing you can do before a shoot is TEST your ideas. See if it works and if you like it. There is nothing better than good old experimentation.

One other thing to keep in mind is what type of footage are you shooting? Talking heads, action???

Hope this helps,

Jim

[Gareth Watkins]

Originally Posted by James Huenergardt

You probably won't want to use any CF modes on the Z1U when shooting on a greenscreen. It halves the resolution (see ww.adamwilt.com/HDV/cineframe.html)

Deinterlacing might work fine. I've tried it both ways with Cineform in After Effects and didn't notice much if any difference.

You won't want to use any filters either.

I usually capture in HDV and key in HDV then downrez in After Effects to SD.

The best thing you can do before a shoot is TEST your ideas. See if it works and if you like it. There is nothing better than good old experimentation.

One other thing to keep in mind is what type of footage are you shooting? Talking heads, action???

Hope this helps,

Jim

Thanks Jim, for your reply... Yes, I've read Adam's site which is why I've used the CF25 in HDV... no visual difference as is isn't halving the SD resolution when down converting...

I'm going to have to provide a downconverted SD version for the Graphics guy who'll be doing the keying with After Effects.. he doesn't have any HDV acquistion equipement...or Cineform, (nor do I come to that, until I get a new PC soon). I may even have to shoot DV to hand off the tape.

I just wondered if anyone has used the Z1 for green screen and how they set it up?

Regards
Gareth

[Matt Davis]

Originally Posted by Gareth Watkins

I may even have to shoot DV to hand off the tape.

Egad - please don't! Both DV and HDV have a major problem for chromakey, in that both formats have low resolution colour info, so without remedial work, DV chromakeys look like they've been cut out with a cheese grater.

Shoot HDV, ingest into your NLE. Ideally, deinterlace 50/60i in post using something that will do an 'intelligent' (motion sensitive) job (e.g. Nattress, DVFilm Maker) then output as a QuickTime movie using PhotoJPEG at 100%, putting the file on a DVD-ROM. Let AfterEffects handle the scaling from HDV to SD and the included KeyLight do the keying.

Originally Posted by Gareth Watkins

I just wondered if anyone has used the Z1 for green screen and how they set it up?

Set Zebras to 70% and light the background so that you get a nice even zebra pattern, then light your talent accordingly. Shoot on manual everything at HDV 50i/60i, and double check that no gain is used, and that black stretch is disabled (the only time I switch it off) - grain makes messy keys. Check your sharpness settings - 8-11, any more and the ringing effects will interfere with your key.

[Douglas Spotted Eagle]

HDV doesn't have huge problems for chromakeying and certainly doesn't look like it's been dragged through a cheese grater, it's a combination of skill and having the right tools.
Is it as good as starting with a better image from a great lens and uncompressed signal? No. Does that mean you can't turn out clean keys from HDV or DV? No.
Shoot HDV, and if you can't ingest via component to save conversion time, then convert to a more friendly HDI than MPEG if you're working in FCP. If you're working in Canopus, Sony Vegas, or Avid Liquid, go ahead and key on the MPEG directly, or better, use the CineForm HDI. If you have Serious Magic (now Adobe) Ultra, even better.
You'll have outstanding results, particularly if you stay HD to the end, prior to rendering your composite.
Matt's advice on shooting is right on the money; follow that plan and you'll have good source footage, assuming you've got lighting, etc.

[Gareth Watkins]

Hi Spot

thanks for your reply..yes I have decent lighting... soi'll go for getting that as good as I can.

however editing in HDV isn't a possibility for this shoot as I'll have to hand off either the cassette or if I shoot HDV downconvert to an external Hard Drive... The guy doing the DVD has no access to HDV editing.

Is is still worth shooting in HDV in thsi case?

cheers
Gareth

[Douglas Spotted Eagle]

Yes. Shoot HDV, capture HDV, convert HDV to a high end codec such as Bitjazz/Sheer, CineForm, 4:2:2 YUV, etc. Ask your editor what uncompressed or lightly compressed codec he'd prefer.

[Chris Li]

Matt,
Are you saying light BG to 70%? same as foreground? I thought 50-60% IRE would do the trick.
should sharpness be reduced from default setting to minus 8 or 11?

thanks,

chris



Set Zebras to 70% and light the background so that you get a nice even zebra pattern, then light your talent accordingly. Shoot on manual everything at HDV 50i/60i, and double check that no gain is used, and that black stretch is disabled (the only time I switch it off) - grain makes messy keys. Check your sharpness settings - 8-11, any more and the ringing effects will interfere with your key.[/QUOTE]

[Matt Davis]

Originally Posted by Chris Li

Are you saying light BG to 70%? Same as foreground? I thought 50-60% IRE would do the trick.

Well, admittedly I'm in PAL-land, and IMHO an even lighting is more valuable than an exact IRE %age, as it's a chroma key after all. I want a good strong colour, which sometimes comes with a few more lumens in the luminance.

Originally Posted by Chris Li

should sharpness be reduced from default setting to minus 8 or 11?

Yes, and I have been subjected to fire hoses for saying this before, but the stock Z1 setting for sharpness (IIRC it's 12) is too much for my eye. I now shoot at 8-10 and will add an FCP sharpen at about 15% if strictly necessary (usually to footage shot at 8). I regularly have to cut Z1 footage with DVCAM from a DSR-570 fitted with a lens that could buy 4 Z1s.

Originally Posted by Douglas Spotted Eagle

HDV doesn't have huge problems for chromakeying and certainly doesn't look like it's been dragged through a cheese grater, it's a combination of skill and having the right tools.

Which is why I have zMatte, DVmatte Pro, KeyLight and a couple of other obscure keyers. Due to the 4:2:0 nature of HDV (and oversimplifying things a great deal) you're only getting a quarter of the rez of your image for keying. Unless, of course, you rescue it by pulling something out of your luminance info (or a difference matte). Even then, you risk the 'soft edge' key look. Otherwise it is going to look blocky. If you do a pure chromakey on HDV and DON'T down-rez it to SD, or do a pure chromakey on DV footage, the big blocky cheese grater edges are there.

I've got chromakey stuff that agencies assume is digibeta, but it's DV and some of it's PD150. I did a chromakey project last year that's one of the best keys I've done, and that was HDV, but it was HDV at SD using the AfterEffects method.

It can be done, but here comes that mantra again: it had better be in focus, it had better be the right exposure, and the camera hand better be in fully manual mode. :)

[Michael Frkovich]

If you want the best chroma key you can get out of this camera, hook to a kona card and down convert to 10 bit uncompressed sd in real time. Use ultimatte advantedge as keyer and you will get perfact keys. Ive done tripple layers of keys using this and if you light well its amazing.

Originally Posted by Gareth Watkins

Hi there

I've run several searches through the board on Chroma Key set up, which have given me all the basic info.
However I've a couple of queries about using the Z1 for this technique. I shall be out putting to SD for a DVD.

Which is the best setting to use to make the keying easier? I often shoot CF25 for SD useage and get good results. Would it be a good idea to use this for green screening? or shoot 50i and then deinterlace with say Virtual dub?

Also would it be better to turn the sharpness down to say 6 or 7 to help avoid green spill? I usually set it at 10 or 11. I intend to light the background separatelyt and backlight my subject.

Finally would using a filter like say a Black Mist or Pro mist help or hinder the technique?
Thanks for any advice on setting up the Z1.
Cheers
Gareth

[Gareth Watkins]

Originally Posted by Douglas Spotted Eagle

Yes. Shoot HDV, capture HDV, convert HDV to a high end codec such as Bitjazz/Sheer, CineForm, 4:2:2 YUV, etc. Ask your editor what uncompressed or lightly compressed codec he'd prefer.

Hi Spot
thanks for that..my editing suite is getting a bit long in the tooth as despite shooting on the Z1, I use it for SD stuff, (DVD & internet) and haven't the computing power, or software upgrades to use HDV native all along the line.

We've not had a need for it..yet!! So I downconvert in camera. We've no budget to go out and upgrade for this one shoot..final product will be DVD.

I've enough software to capture the HDV and convert to something like higher res .avi files. Is this worth the extra effort?

But the other issue is that all the background archive material will be SD... At what point will I downres so it makes a difference..compared to shooting all in DV or in camera downres'd HDV???..
I guess I'm tying myself in knots here...
Cheers
Gareth

[Douglas Spotted Eagle]

It's definitely worth the effort, IMO. The HDV image is as good or better than most any Betacam you might have, and it's useable for the future.
If your backgound is SD, you might want to convert straight to uncompressed SD for this one.

[Gareth Watkins]

Originally Posted by Douglas Spotted Eagle

It's definitely worth the effort, IMO. The HDV image is as good or better than most any Betacam you might have, and it's useable for the future.
If your backgound is SD, you might want to convert straight to uncompressed SD for this one.

Sorry to labour this one, but HDV is new to me despite having had the Z1 for a while... I'm trying to find the best solution.
What would you suggest as the best way to convert to uncompressed SD.. I takre this is avi..

We use Premiere and After Effects? ... Until I update my PC I've not got any of the higher end software.
Thanks again for your help
Gareth

[Gareth Watkins]

Ok... thanks to all for your input..

Here are some of my findings...
1) Yes shoot in highest res..
2) Deinterlace.. I use Virtualdub Smart Deinterlace.

Otherwise in DV.. I shot HDV and downres'd in camera as it was not possible for this project to use HDV..pity!!

I used After Effects with Keylight plug in.. this is a great plug in and gives excellent results. Very powerful..

Still photo backgrounds give a cleaner and sharper result then motion backgrounds... I guess for the same reason HDV gives cleaner keys... you start from a higher res image...

I think for my next project I'l shoot in HDV... use a still background and down res to DV for output, as I'll have all my elements in HDV or stills... this project unfortunately and had all the background footage in DV, so we stuckwith this for the keying...
The AF and keylight combination was very nice though...

regards
gareth