EX-1 (or EX-3) for Chroma Key?

M

MitchLewis

Well-known member
Okay, I think the EX-3 is finally the solution to replace our Canon XL-1S. I like most everything about it. The only thing I'm concerned about is how the footage will work for chroma key. I read that it records 4:2:0 not 4:2:2 like the HVX can at 50mbs.

Our XL-1S footage (4:1:0?) was difficult to chroma key, even using After Effects>Key Light. I'm looking for a better solution for the few times a year we'll shoot chroma key.

Maybe taking the HD-SDI output and recording it to ? would work. Could I bring a MacBook Pro with Final Cut and record HD-SDI some how?

Sorry I'm pretty new to all this HD stuff. My years of experience has been with DV footage.

Thanks!

Mitch
Videographer/Editor since 1987 - Worked with 2-inch | 1-inch | 3/4-inch | JVC D9 | DVCam | But no experience with HD formats
 
The compressed (HQ) footage keys quite well. There's some artifacting in the mattes but in motion, using Keylight, you'll be pleasantly surprised. It's worlds different from keying with DV.
 
The EX1 keys great from the native codec with just a bit of post blur applied on the chroma channels. Keys even better from the HD-SDI out. You could certainly record HD-SDI via an AJA IO breakout box hooked up to your Macbook and a SATA raid to ProRes. It's a working setup I've used with the F900 a number of times.

Here's a bluescreen keyed over grey split screen test I shot literally out of the box with the EX1...

http://ftp.datausa.com/imageshoppe/outgoing/EX1/EX1_compressed_vrs_uncomp.mov

Tips; Turn off detailing, use -3db and don't use any cine gamma or matrix (I like standard gamma 3, tweaked as described). You want the sensor as linear as possible. I'm now experimenting with turning off the knee as well with my controlled lighting green screen work.

I'm doing a side by side same subject blue screen test of the EX1 (both native codec and uncompressed 8bit) against the RED on Thursday and will share the results.

Regards,
 
Thanks guys!! Your info is greatly appreciated! Sounds like the EX-3 is the camera we wanna get. Now we gotta wait for it to be released.

OFF TOPIC: BTW, is there another forum that's as good as this one, but caters to the EX-1 (EX-3)?
 
Jim Arthurs said:
Here's a bluescreen keyed over grey split screen test I shot literally out of the box with the EX1...
http://ftp.datausa.com/imageshoppe/outgoing/EX1/EX1_compressed_vrs_uncomp.mov
Click to expand...

Thanks for the test.
Has to be said that the difference is detectable, but quite marginal. The XDCAM compression does seem to be creating a very thin edge of sharpening style artifacts. While this is visible against your test grey background, it would probably be less visible against a more naturalistic background. I would guess it would also be difficult to spot if you were scaling to 720p or SD. I suppose one real advantage of capturing via SDI is that you can also capture to cards, giving simultaneous backup (which would be good on an expensive studio shoot). For lower budget productions, I would have to question whether it is worth the extra hassle and expense of setting up a tethered option. I think people are jumping to the conclusion that the XDCAM codec has flaws based on theory, rather than practical experience, and people are going to be setting up expensive uncompressed raid capture solutions with massive storage, when no-one is going to be able to see the difference!
 
Jim Arthurs said:
The EX1 keys great from the native codec with just a bit of post blur applied on the chroma channels. Keys even better from the HD-SDI out. You could certainly record HD-SDI via an AJA IO breakout box hooked up to your Macbook and a SATA raid to ProRes. It's a working setup I've used with the F900 a number of times.

Here's a bluescreen keyed over grey split screen test I shot literally out of the box with the EX1...

http://ftp.datausa.com/imageshoppe/outgoing/EX1/EX1_compressed_vrs_uncomp.mov

Tips; Turn off detailing, use -3db and don't use any cine gamma or matrix (I like standard gamma 3, tweaked as described). You want the sensor as linear as possible. I'm now experimenting with turning off the knee as well with my controlled lighting green screen work.

I'm doing a side by side same subject blue screen test of the EX1 (both native codec and uncompressed 8bit) against the RED on Thursday and will share the results.

Regards,
Click to expand...

Sorry, but I'm not sure if I understad. You stood in front of a blue screen and keyed in a grey background? Both sides look great to me! I can't tell the difference. Maybe it's because I'm watching the movie on my laptop in Quicktime?

Thanks for doing this test. It's VERY helpful.
 
I heard that recording the HD-SDI signal WHILE recording onto cards has no benefit - its 4.2.0 compressed already , no wonder they look identical... can anyone confirm?
 
Nicky said:
I heard that recording the HD-SDI signal WHILE recording onto cards has no benefit - its 4.2.0 compressed already , no wonder they look identical... can anyone confirm?
Click to expand...

Yes, you heard wrong.

The SDI output is available while recording to the cards.
The SDI is pre XDCAM codec and is 4:2:2 10 bit at that!
 
I just finished some RED (3 REDs vrs 1 EX1... no fair!) vrs EX1 tests yesterday. Fun day. Results after I've done some processing.

I also took the EX1 to Convergent Designs yesterday and had them put it on their high dollar HD-SDI testing equipment.

There is no doubt, the signal is a true 10bit signal with very nice specs overall.

Regards,
 
Nicky said:
I heard that recording the HD-SDI signal WHILE recording onto cards has no benefit - its 4.2.0 compressed already , no wonder they look identical... can anyone confirm?
Click to expand...

No, the live output is before compression while recording to the cards... and look closer, there are differences.
 
Jim Arthurs said:
No, the live output is before compression while recording to the cards... and look closer, there are differences.
Click to expand...

LOL... Yes I hear you all, Im obviously wrong - I knew it was proper 10bit 422 uncompressed just wondering about the simultaneous output. Jim there are SLIGHT differences but its a pitty you put the EX1 on the bad side where the problem edge is (I hope we are talkin bout the same clip)

I have not been round for a while and things advance quickly on these forums. hehe:smile:
 
I got this from another message board.

Actually, the Ex1 outputs honest to goodness 10-bit 4:2:2 at all resolutions via its built-in HDSDI/ SDI interface.

Now, a word about "color space". In the old SD days, 4:4:4, 4:2:2 and 4:2:0 had absolute meaning and direct correlation to the picture quality (luminance and color resolution). In the case of HD, 4:4:4, 4:2:2 and 4:2:0 are relative. Thus, these ratios have no "real" meaning anymore. Therefore, it would be possible for an HD format with small luminance and color spatial resolution to claim 4:2:2... so, the only way to compare is to count the actual captured pixel resolution. Once, you know the exact number of luminance pixels stored, you can apply the ratio to compare apples to apples (for a given aspect ratio).

For compositing, all that is necessary is for color sampling to be tight enough for the keyer to effectively detect the edges. You will find that Ex captures 960 color pixels in the horizontal direction capturing a higher color resolution than some HD formats. The color sampling is also halved in the vertical to 540, which is still suitable for good keying. Lastly, at the core of modern compositing engines are sophisticated keying algorithms that even look at luminance transitions to more accurately detect the edges. Please try keying with Ex 4:2:0. I believe you will be surprised how good keys you will be able to achieve.

Sorry for the long winded reply. I hope it helps.

Juan Martinez
Senior Manger Technology
Sony Electronics


Juan Martinez
Click to expand...
 
I can real world verify that the HD-SDI out is 10 bit. Convergent Design was kind enough to hook my EX1 up to their high end test gear and check for me.

Regards,
 
Good info but did i miss something? Which keying program was used? Is their a Keying program that works best with the EX-1?

How does FCP/color keyer work with the ?

thanks much!
 
Jim Arthurs said:
Tips; Turn off detailing, use -3db and don't use any cine gamma or matrix (I like standard gamma 3, tweaked as described).
Click to expand...

Jim, I'm wondering if you still think one shouldn't use cine gammas for green screen? I have had good results with cine1.
Why is it you think they are not good and which gamma do you use then, Rec709 (Std3)?
Thanks.
 
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