Tips for chroma keying in VT4
 

Hi All, I am about to embark on my first chroma key job and I was wondering if anyone had some killer tips for me.

I will be using VT4 / Sony FX1 HD and will be doing a full body shot.

I am looking at using a twist & Flex 8' X 8' background screen with integral skirt ( available in G/B for £115 )

It is the light options I am most confused about.

Obviously with the toaster/FX1 I have YUV in - the camera has zebra/WB/Iris etc control and armed with these tools and doing a live set up - I should be able to avoid most post nastiness - but there are so many options for lights from basic photo studio set-ups @ £180 to kinoflo stuff and ring and screen things costing, well too much.

Can anybody recommend a reasonable light solution for this scenario that makes best use of the equipment I have already?

Also being mainly a 3D guy - I'm not that up on the vector scope etc - other than the manual - does anyone know of some easily digestable information on the use of these VT parts to enable me to get the most out of them in this application - sorry if this is all a bit newbie.

Thanks in advance

3DBob

There should be some good tips on Chroma Keying if you do a search here.

For now, here is a quick list.

Even lighting on the background is a must.

3 point lighting on the subject. Key, (one side), at 100%. Fill (other side) 50 to 70%. Backlight, usually more from the side of the fill light.

Tungsten is normal, but other options are available. (Just don't mix light types, i.e. tungsten and florescent etc.)

For a good key, do not dump through DV if possible. Use Component or S-V if possible.

Sorry for the quick post, but gotta go. I'm sure others will chime in with more detail.

One more thing...DON'T experiment on your clients time. If you are this new to Chroma Key, do some tests and refine the process. You obviously are doing your homework by starting here.
I wish you well.

Hi 3DBOB,

Welcome to the VT side.

Well, First I need to know if you are working with VT3 hardware or VT4 hardware...and which software?

I have already setup Virtual set internet studios with the Sony HDV FX and VT.
If lighting is an issue or you have a too small space to light the talent and bkd seperately...then I would strongly recommed the Reflectmedia chromatte ring and material...that is what we used in this VR studio and it worked fabulous!!!

With a couple of photoflexs with softboxes...it looks great...and without the cost of the kinoflows...Actually with reflectmedia you could light it with a flashlight if you want as long as it is not directly from the camera's point of view.

If you are going to work more traditionally then I would

1) light the background with Kinos..with an even level

2) I would then use more Kinos to light the talent or light with softboxes.

Setup the bkg to be a half to a full f stop LOWER than the talent...this will give you the best ability to key...and ONLY record direct to disk...don't compress to DV.
Also if VT's keyer doesn't give you the level of key you desire then use Aura or Mirage...much more control with them than with VTEditor...thou it can create decent keys if setup correctly..

Hope that helps...get back with me in regards to your setups...for that will determine if you should go with component out of the Sony or y/c...okay ;)

Cheers,

Thanks Ted and Ray - very useful tips,

I have a VT3 board with the latest VT4 software.

Cheers

3DBob

Fantastic...

Then I recommend that you take the SD component output from the Sony HDV FX.

Now how much room does your talent need to move in? Will this be indoors or outside?

I would also check to see if someone has a chromakey stage that you could rent,
then bring your gear into it...then the lighting etc...should already be there.

If you can swing it thou the reflectmedia is a good way to go since you do low level lighting if you need...also note that the Sony camera has very good pickup.

Put try to keep bkg levels half to a full stop lower than the foreground ;)

Cheers,

Ray, just to confirm, I thought I read somewhere that the Sony HDV cameras, unlike most DV cameras, output is already converted to DV. If that is the case this camera is not the best choice for chromakeying, if in fact he has a choice of cameras, right?

bradl

We made some keying tests with the Z1, firewire and SD component output simultaneously connected to VT4. There is defintely a difference in Quality. Firewire gives the typical blocky artefacts while Component out is much smoother. But unfortunately it doesn´t look like 4:2:2, so I guess it´s only 4:2:0 Component out.

Finally we ended with the key-footage in AfterFX

alexx

Well the output I saw didn't look like it was thru DV compression..it was crystal clear and was an analog signal...I'll have to check, but I do not believe it's been compressed if you are just outputing from the analog outputs of the camera at least thru the component outputs.

The keys that this made were beautiful...and that was with the LIVE keyer...granted not for high end post but for local and internet broadcast it was fine and that was even with Glass and other transparent objects and a the moderator is a blonde shoulder length female...It looks GREAT.

Cheers,

I also don' think that it is 4:2:0 there is too much color information for that to be true...

If that was the case then the keys would be like DV is now..and that isn't the case either...the FX at least keyed better than ANY DV camera I've ever worked with...and it worked just like the Ike's and Sony broadcast Studio camera's I've worked with in the past...How are you comparing the signals?

Cheers,

Ray

I compared IMX material copied via component to a Beta PVW.(Already taped vs. live Z1) My subjective feeling is that colorspace in Z1 looks "thinner".
But even here for best keying results I had to use AfterFX.

But as you said for keying, Z1 with its Component output is not compareable to any other DV-Cameras

alexx

The FX1/Z1 analog out is supposed to be downstream of the encoder, but for the life of me it doesn't make sense, the component out, both SD and HD looks nothing like the encoded HDV signal. I wouldn't say it's artifact free, I like the term above 'thinner color space' better though, but what's coming out of the component out on the camera is nothing like what comes off the tape HDV.
I'm looking for an economic way to capture the component out HD straight to a drive array, any ideas? So far I've come up with a blackmagic decklink and yuv to sdi converter plus associated hardware, but that weighs in at around $6000 and I haven't even tackled audio yet (the decklink is aes/ebu)

Thanks Eric,

I'm still trying to find out what is actually going on...as you stated the analog outs do not look anything like the HDV and the color is much more present and keyable from the analog outputs..in fact it looks beautiful. I can't even find the spec from which the chips are sampling at for color space...do you know where I can find this info? Cause the analog outs don't look like 4:2:0 do they to you?
and yet it isn't a full 4:2:2... to much alchemy going on here ;)

As for inexpensive HD yuv to HD-SDI...there are several glue boxes that do will do this and I believe one will also do AES...other wise take the analog audio and convert to AES...and see how the timing is going into the BMD. those boxes should be around $1,000 and the BMD is $1,500...then the camera and cables.

Cheers,

Don't Laugh
 

Hi Guys,

Thanks for your help on this.

Looking into all the options and pulling in some of our manufacturing contacts we have prototyped a Keying solution using retro reflectivity. Just made sense to make use of the two electronic degrees we had in the office.

Here is the very first Clip recorded with the current version. Sorry for the Codec. Jpegs to follow.

We will be looking to make custom sized Retro-reflective studio drapes - anyone interested? They truely are amazing - this key was done with a VT3 with VT4 software, live in our office. We used the 2 available 20W Low power floro bulbs and a red 40W filament bulb and our FX1.

Enjoy

3DBob
The Image Refinery

Screen Grabs.

3DBob

Made a retro reflective fabric? Based on what process/principal?

Hi all,

I just poped into this thread since i had my first and - bad - chromakey experience a few months ago. I'm looking to redo it since the project is still ongoing.

I'm not a chromakey expert so i don't know what the good and bad is about any one technic but i would seem that the more traditional way of using a green/blue screen or paint that requires two lighting setup's - one for the screen or set and one for the talent is more problematic.

It would appear that the Chromatte/ChromaFlex - Litering technic is the way to go since it appears to create the same net effect without having to worry about the set or screen lighting.

Comments?

BTW - 3DBOB,
Would you please chop up your attachment into three files so i don't have to slide the screen around to look at them all. ;)

Ok peoples,

We made a new illumination device and ditched the 40W bulb in favour of another 20W floro in a desk lamp.

Set up for chroma key was 4 mins. YUV from FX1 as source. A dance show my girlfriend was in as background to have something nice to key over. All keying done live with the VT!

What follows are some stills (we've just cropped the overscan a little) and a video can be downloaded as a reasonably high quality DIVx 15MB 25 seconds from here

http://www.icws.co.uk/retro/Key2_DivX.avi

Next week we'll do some full body stuff if we get time.

This is so much fun (I never thaught i'd say that about Chroma Keying) - I can't wait to use it on the website job were doing. and to think I was going to hire lights and a sparky for well over £1000 for just this job!

Regards

3DBob

Picture number 2

Picture number 3

Picture number 4

Picture number 5

Picture number 6

I know I need to clean/clip my nails - I have been re-modelling my bathroom these past 3 weeks in the evenings.

3DBob

"Looking into all the options and pulling in some of our manufacturing contacts we have prototyped a Keying solution using retro reflectivity. Just made sense to make use of the two electronic degrees we had in the office. "

What is the basis of this prototypical retroreflective material? Is it like a scotchlite with monodirectional beads, or like chromatte with multidirectional? Who manufactures it for you? Are you using an LED array or a beamsplitter?

Hi Eric,

It's 3.20 in the morning here and we were working on this till 6.15 am yesterday - so I'm about to crash.

We considered a beam splitter and maybe using a few luxeon stars - but since my brother ( an inventor ) is allready into LEDs in a big way with his products:-

http://www.spacewriter.com/

LEDs seemed to be the way to go. All his products require LED matching and his companys taiwan division is pretty expert at it.

We have developed a range of dimming solutions and are honing the controller circuitry with every iteration.

With regard to the fabric - it works as long as the incident angle isn't under about 10 degrees (this is a guess) for convex folds less critical for concave. Bottom line is - it works and works well, this maybe partially due to beam spread on the LEDs, something that we are investigating. Not at liberty to discuss anything that may be commercially sensitive as we are wanting to give the video etc community a good product at a good price.

The fabric should work fine with the LED based light sources that I believe you supply.

Regards

3DBob

How much are those iBall+'s? They would be great for my office and go well with the other spherical toys like my plasma lamps.

What you have is similar to scotchlite, in terms of angularity at least. You may need to worry about parralax though as your screen gets larger, and moulding the material into a sphere is no mean feat. But if you can make it cheaper than scotchlite without stepping on 3m's toes you could have a good product. The beamsplitter would eliminate the nonkeying areas you see in closed loops (like the one your thumb and the handle of the mug form), another method would be to place a cone (like a lens cap) in front of the LEDs and ramp up the brightness. Good luck, let us know how you get on and get some sleep will you?

Hi Eric,

The original system developed by our beloved public institution - the BBC is detailed here,

http://www.bbc.co.uk/rd/projects/virtual/keying.shtml

as is customary with anything BBC it is well laid out and informative. Our fabric appears to be broadly equivalent to that used by them. Certainly for many uses I dont think if it has additional limitations, they will make a practical difference to its use.

We will be looking to initially make specific illumination devices for the sony FX1 and Z1 with all the kit to make it work with the toaster. For a Pro/Semi Pro these are great cameras and many people over here are snapping them up for their SD work.

The iBalls like all spacewriter products are great - you can program image sequences / scrolling text to come up at specific times in the year and program them remotely over a phone line. The animations can be cloned or rotated in either direction round the ball. Send them an e-mail - I know they are looking for distributors - maybe there is an opportunity there for you?

3DBob

Well, that is Chromatte, you should be getting angularity on the order of 80+ degrees, not 10. Are you getting the material from Reflec?

I think you misunderstand me - in your language our fabric works up to around 80 degrees We'll maybe do a video test and post it for you so you can see it in action.

3Dbob

Forgive me if I seem a trifle wank, but if you are using Chromatte, and LEDs, what's the innovation?

I don't know about the keying, but I wish I worked with dancing girls ;)

I think you misunderstand me - in your language our fabric works up to around 80 degrees We'll maybe do a video test and post it for you so you can see it in action.

3Dbob

Hey bradl - it's a hard life

Hey Eric, I never mentioned innovation - I just said that we can produce the relevant stuff for wicked chromakeying at a significantly lower cost to the end user - and with Flash 8 now allowing transparent video ( read layered flash video with programming ) I see a whole new generation of users and broader uses for the technology. Imagine a single jpeg background - then you have ten alpha characters (captured with retroreflectivity) that can be layer at programmed intervals and looped out of phase.

In some of my own work over the years - I have constantly had to crop out images of objects and people for web and interactive stuff - we will produce packs that allow these web artists to leverage the auto crop that Chromakey provides.

When I have done Cromakeying in the past using matt painted cycloramas and kilowatts of lighting, it has always been an uphill struggle with things like spill and all the rest of the nightmares.

3DBob

Yeah, spill's a *****, but between Chromatte and AdvantEdge it's not really a problem any more. Forgive me, it just seemed to me that your wording implied that you had invented a retroreflective fabric, something which I would be really interested in. In terms of working with Chromatte, you might want to drop John Herbert a line; jherbert@reflecmedia.com he's done more work with Chromatte and related issues than anyone in the UK. If you are going to build your own illuminating devices I really would recommend some kind of beamsplitter or some other method of originating the illumination from the center of the lens, I had some good luck using a teleprompter and a gelled and flagged studio light, all I was missing was a lens on the light to focus it.

I really can't see anything could be much better than what we have fabric wise - and we are getting very good live results with our current LED ring and VT4 - The next generation of illuminator/controller should be another leap. I agree a beamsplitter would be a great way to go - and maybe we will give this a go later down the line - we have thought of using Luxeon 5W stars for this with some sort of diffuser. This would mean only 1 light source and make it MUCH simpler to create a dimming controller. The same set-up would be applicable to a wide range of cameras we think also without messy adaptors.

I think there are many out there that would like to have this capability but are put off by the normally high price ( though it is much cheaper and better than traditional methods ).

3DBob

Yes, Reflec has really gotten the refinement process down very well, today's Chromatte is easily four times brighter than that of five years ago. But in terms of the savings, are you planning on offering lower cost LiteRings and Controllers?

Eric/3DBob/et al,

We have need of chromakey rarely, but if it was high quality, easy to set up and afforadable we may use it more. Eric, in fact, we have disk from you with Virtual Sets that was won as a door prize at NAB a couple years back.

Right now we have Ikegami HD studio cameras, JVC D-9 ENG/EFP cameras and we are buying 3 Sony HDV Z1 cameras soon. Also we are attending NAB next month. I would love to propose a mobile easy to set up Chromakey production solution to the bean counters. Currently we use green screen cloth backdrop and have used Chromakey paint, blue and green, but have never been really pleased with the results.

My questions to you guys (or anyone):
1. What portable, afforadable chromakey camera solution do you recommend?
2. How much will it cost?
3. Other than VT4, what chromakey software would work best with this and the new Sony HDV cameras (we use FCP, AE and PP as well)?

Thanks so muich!!

Hi Bradl,

We can offer custom made drapes with either flameproof black bolton twill or flameproof blackout wool in serge black (the latter is heavier) with eyelets for hanging. They will be significantly cheaper than the competitor and will allow for a reseller to make a sensible margin. We will also produce smaller set-ups for the web development market.

At the moment our illumination devices and controllers are being honed and therefore I would recommend getting a competing product to work with our fabric. Our initial product will be specially designed for the FX1/Z1 as we believe they are the camera of choice at the moment in the mass market pro/semi pro arena. Doing this will allow us to pack as many LEDs as possible as near to the lense as possible. Our illumination device and controller will be cheaper than those available when it is released but that is some way off.

AdvantEdge is a great tool in a class of its own as Eric says but the Toaster can do a great job as we have discovered so far.

We are looking to make daylight diffuse boxes and are working on getting the correct balast and choosing the right bulbs for full colour rendition we may consider commercialising the design - they are really gottoflos at the moment - but really this type of chromakeying allows you to use a wide range of lighting including cheap floro bulbs and people may well use whatever they want to get the right look. It even works with really low light.

Our set up took four minutes from Toaster off to successful key with 3 X 20W £1.99 floro bulbs. And for run of the mill keying work a lot of new customers would not be unhappy.

3DBob

Hey Brad,
Reflecmedia makes two self standing popup models, the Chromaflex, and Chromaflex Compositor:

ChromaFlex
7' (H) x 7' (W) Chromatte Collapsible Screen
1 LiteRing (Small or Large)
LiteRing Controller and Power Supply $2250

ChromaFlex Compositor
50" (H) x 50" (W) Chromatte Collapsible Screen
1 LiteRing (Small or Large)
LiteRing Controller and Power Supply $1995

More info on Chromatte can be found here: http://www.virtualsetworks.com/Products.Chromatte.htm

We also offer Chromatte Rentals for the Chromaflex, Small Studio, and Studio curtains: http://www.virtualsetworks.com/Produ...tte.Rental.htm
Reflecmedia, as well as I, will be at NAB in the Bogen booth and a few other booths as well.

FYI, we also have a new pack of Virtual Sets coming out for NAB: Virtual Set Pack volume 5: http://www.virtualsetworks.com/Produ...ualSetPack.htm