Z1 and Greenscreen

Marty Smith · June 10, 2005

Does anyone have experience with these cameras and greenscreen?

Shooting a series of commercial on 16mm but using HVR-Z1 with digi-green for the advertiser's pieces to camera. We're scared of film with her as she needs an autocue and a bottle of wine for 7 second grabs. Bound to roll of a good hour of tape. Has anyone noticed problems or issues with greenscreen? Any infometion would be great as I'm not sure if I'm gonna be able to test thoroughly.

Thanks.

Brant Collins · July 7, 2005

I just got a HVR-Z1U on loan as a demo from my local dealer. I am going to do some green screen tests tomorrow

David Mullen ASC · July 7, 2005

The color subsampling is 4:1:1 so you'll have the same chromakey problems as with Mini-DV. It might be slightly better since all colors will have more resolution than DV but still, HDV is not an optimal format for chromakey.

David Cox · July 7, 2005

If your final delivery is standard definition, then there is a trick that can help.

The HDV spec sheets claim that is a 4:2:0 colour system (although I reckon this should be 3:2:0 cos it only records a width of 1440 not 1920 pixels for its 1080i setting). So this means that the colour part of the signal is actually a quarter (or a third) the resolution of the black-and-white signal. So this is why you're chromakey would suffer aliasing and lack of detail if viewed at HD. However, if you use a software downconverter that cleverly converts your YUV HDV to RGB SD, you could theoretically end up with an RGB SD signal full ish resolution for all components (because there are 720 colour samples per line, and every other line contains each colour component so 520 lines in all).

That only works for SD though and is a trick we developed to shoot HD-CAM green screens for standard definition masters.

It all goes wrong if you select the 720p setting, as opposed to the 1080i setting though because the resolutions go down. It also depends on your software doing a clever down convert.

rogala · July 8, 2005

You can download few greenscreen shots done with fx1 on:

http://www.seriousmagic.com/help/ukindex.cfm

With good chromakeyer ( I checked them with DS chromakey) effect is wonderfull!

Or You can buy Ultra2 from Serious Magic.

Brant Collins · July 9, 2005

I demoed the Sony HD and took some footage of my green screen set. I tried it under bad lighting just to see haow it would key in FCP5. It keyed really well and very crisp. There is much more information to work with. Now I recorded to the tape on my test but as I understand you can capture to your NLE uncompressed? Do not know if it is still 4:1:1 or not? Anyway it keyed well

Brant Collins · July 9, 2005

here is a still from the test and the results. As you can see I did a bad lighting job just to see how far I could push it. This was done with the standard BLUE CREEN SCREEN KEY in FCP5. If the light were set right the key would be awesome.

Brant Collins · July 9, 2005

here is the set up

r_j_rock · July 11, 2005

Just downloaded the HDV samples from serious magic, and ran a test in Premier 6.5 with Ultimatte.

Looks great. Far better than any DV keying I've done, and down rezzing to DV, it still looks great. All I did was a single click in each of the clips to select the backing color, no tweaking at all. I bet if I spent more than ten seconds setting it up, it would look awesome.

I don't own the Z1 yet, but this little tidbit just sold me on it, even though all of my work is currently SD out, this will save alot of time during compositing (which I do quite a bit).

I'm surprised I didn't see more aliasing. everyone I've talked to cries about this, and I just don't see that much.

Edited July 11, 2005 by r_j_rock

Bob Hayes · July 11, 2005

I can?t wait to see your results. Also, how do you post pictures on the site?

Another question on your green screen. I noticed there was quite a lot of green bouncing off the shiny chair which I?m sure will be a pain in the ass later. What is the solution to dealing with these reflections.

Luke Prendergast · July 11, 2005

Light the talent seperately. Unless of course you're deliberately abusing the chromakey as in this example.

Brant Collins · July 11, 2005

Our set is for LIVE TV broadcast and we use the hardware switcher on our ECHO LAB switcher. Plus we tweek the lighting and settings to get a good key. Of course this is done with Broadcast Hitachi cameras running SDI to the board.

I did a bad light set up on my test just to see if the HD was easier to key. We do key DV but it is really hard to get a good key. I have a DV green key plug in (DV Garage) I think that is what it is called. It helps the key but always looks fuzzy on DV. The HD sample keyed razor sharp. I usually would do a garbage matte to key out the bad areas but this example was just a test. I had the camera on demo and did not have time to try setting up a good key. But I can tell from my test the HD will key great