Disappointing image quality, especially for chroma keying
 

Today I did some green screen tests and I am surprised how badly the image coming from the FS700 is suited for chroma keying. The recorded chroma-data is just of pretty low quality. I guess even my iPhone provides better footage for chroma keying, it's just amazing especially for the price point of the FS700.
Here are two examples (100% crops):
http://dominik.ws/fs700_chroma_key_test1.png
http://dominik.ws/fs700_chroma_key_test2.png
They are in lossless PNG-format and no further compression was added, so you can try yourself to key them. I have used AE's KeyLight.

Re: Disappointing image quality, especially for chroma keying
 

It looks like you may have a couple of issues with your setup looking at the images. For one your shutter speed is too low. You want to minimize motion blur when keying. This is a time when you want to break the 2x frame rate rule. Use something in the range of 125 and see if your key improves.

In the image of the woman in particular it looks like the focus on the person is soft. You don't want to shoot a green screen with a wide aperture. Stop down to f/8 at least and light appropriately. Keep the gain below 6db.

When you make errors in setup and operation you create more challenges to pull a good key since the codec is 4:2:0. You will get better performance if you use an external 4:2:2 recorder.

It looks like you have some issues with chroma subsampling on high contrast edges too. A 4:2:2 recorder will certainly help there.

Re: Disappointing image quality, especially for chroma keying
 

The focus was spot on. The softness comes from the low resolution the FS700 delivers. Especially the chroma-channels are far more soft and artifacting than what is possible with 4:2:0-sampling.
In this picture I converted the pictures in Photoshop to Lab-color and extracted and auto-contrasted the a- and b-channels:
http://dominik.ws/fs700_chroma_channels.jpg
Look for instance at the huge artifacts at the right edge of her dress. This is not concerned with 4:2:0-sampling but rather with abysmal debayering. This is so bad that even after down-conversion to 720p the artifacts are clearly visible. So concerning the chroma-information you should call the FS700 rather a SD- than a HD-camera.

Re: Disappointing image quality, especially for chroma keying
 

That is odd. I'm able to get pristine keys out of the 700. I have an outboard 422 recorder but have found it isn'tt necessary unless the background is not properly lit. Looking at your images, it does appear soft, but that is either focus, a missed setting, or a very inferior lens. Also, the backdrop is very poorly lit and the color levels look washed out. I'll post an example of the camera's output using the internal codec when I get back to the studio.

Re: Disappointing image quality, especially for chroma keying
 

I would really like to see your results.
I've used here the Canon EF 24-70mm f/2.8L in conjunction with the Metabones Speed Booster. Yes, I set the detail-level to -7 to achieve a more natural look. Any higher setting just makes it look more like video in my opinion, but no additional detail is revealed.
The colors look washed out because I used the cine2-gamma and set the exposure as high as possible to get the maximal signal/noise-ratio. But it doesn't matter if I lower the exposure, change the gamma or crank up the detail-value, the chroma-channels stay blurry and artifacty.
The cheaper PMW-EX1 from 2008 (which is in many ways much more professional and capable) for example gives me much better results at chroma-keying (also with internal 4:2:0 recording). I can only hope that there will be soon a 4k-recording possibility for the FS700 which makes the whole setup not more expensive than a Canon 1D C.

Re: Disappointing image quality, especially for chroma keying
 

If you have an EX1 that is what you should be using to shoot green screen for sure. That is a totally different animal.

An EX1 with a 4:2:2 recorder is an EXCELLENT machine for that task.

Re: Disappointing image quality, especially for chroma keying
 

I can't imagine why the sharpness is so poor = in fact, SD DV looks sharper than that? The other thing is that the green colour looks light green, and nowhere near how it ought to look for a successful key? Something is very wrong. Have you got a shot from the camera shooting in ordinary light? Is that sharp and reasonably saturated? The lack of sharpness and odd green colour are working against you too!

Re: Disappointing image quality, especially for chroma keying
 

http://www.dingodigital.net/Public/GS-keyex2.pct

http://www.dingodigital.net/Public/GS-keyedex.pct

Re: Disappointing image quality, especially for chroma keying
 

Was it shot in slow motion?

Re: Disappointing image quality, especially for chroma keying
 

I could certainly work with that Will.

Re: Disappointing image quality, especially for chroma keying
 

Chromakeying, especially with compressed video, is the one situation that calls for detail in the camera. The camera can add the edge, pre-compression, and if you find it too crisp inside the key, you can soften after the key.

It also helps to add a bit of saturation to the green channel, in camera.

Finally, if you have the room in your studio, add a 1/2 plus green gel on your cyc lights (or whatever lights you're using to light the backdrop). If you do this, the lights can't have any spill on the foreground. The less variation in the green, the better the key.

I have a PP dialed in just for greenscreening - now if I could just name it.

Re: Disappointing image quality, especially for chroma keying
 

This was not shot on a FS700. It looks like MPEG2-compression. Which camera was it?

No, it was not shot in slow-motion.

Can you post the parameter-values of it?

Re: Disappointing image quality, especially for chroma keying
 

Dominik, you should check the infinity focus setting on your SpeedBooster. It's a known issue - that thing easily gets out of whack, and screws up focus on attached lenses. I had the same problem with softness when using the SpeedBooster, and after some adjustments and trial and error today, it is MUCH sharper, and behaving like it should. This camera is absolutely sharp, as I knew from using the non-Speed Booster adapter successfully. Check your adapter, mate.

Metabones - Infinity adjustment (Speed Booster? only)

Oh, and I should add that I'm using new Canon EF lenses in the L series. So, my lenses are just fine.

Re: Disappointing image quality, especially for chroma keying
 

The speed booster introduces additional chromatic aberration. The 24-70 L series lens is a poor performer in the CA arena already, there's already been a lot of discussion about this. I'd suggest your setup is pretty much a worst case scenario for getting a decent key.

Re: Disappointing image quality, especially for chroma keying
 

The chromatic errors created by the fs700 are orders of magnitude larger than those coming from the optics. Using a better lens would be a drop in the ocean.

Re: Disappointing image quality, especially for chroma keying
 

Chromatic aberration is determined solely by glass. It's a byproduct of the qualities of a lens, not an image sensor.

Re: Disappointing image quality, especially for chroma keying
 

I still have an EX3 I sold my EX1R a while ago, but I have shot a lot with them both.

The EX cams are very different cams than the CMOS C size cams now so popular. I have a FS700 and a C100 and I love them both, they produce wonderful images when used and set up properly.

I love the lens choices and the SDOF possibilities. One thing I know is that the DR is much greater 3-4 stops more than the EXcams.

I can and have got great Chroma keys with EXcams and the FS700/C100. All these cams do better with 422 external recording, but a well lit key works well even 420. The key is a good well lit scene. The biggest thing in keying is to get rid of spill and to have a wrinkle free even BG that is preferably far in the back of the talent. I often add -blue or -green gelled lights on the side if spill is a problem.

I still use the EX3 a lot it is so easy to nail focus and it does produce a somewhat videoish contrast shot that looks good to many people right out of the cam. The large sensor cams are much harder to focus (I think a lot of times people complaining of soft images they are just OOF).

Also I try to shoot where lenses are the sharpest, usually 2 stops down or so. Wide open or stopped down more is generally much less sharp and that seems to be more obvious on larger imagers. A good lens in focus will give a very crisp image on the FS700. I have not tried the Metabones booster yet, but in general optical additions to any lens reduces quality.

Just a couple thoughts after reading this thread.

Re: Disappointing image quality, especially for chroma keying
 

Yes, but I was talking about chromatic errors, not aberration. The sensor of the fs700 is great for sure. But if the DSP of the camera produces junk, also a 60k$ lens from Fujinon won't help very much.
Putting a HD-lens in front of a SD-camera won't make it a HD-camera. ;)
(Yes I know, the fs700 isn't a SD-camera)

Re: Disappointing image quality, especially for chroma keying
 

The C100 is much better than the FS700 in terms of resolution. Can you give examples of chroma keys you did with the FS700?

Re: Disappointing image quality, especially for chroma keying
 

Misquoted... I actually haven't tried any chroma keys with the FS700, though I'm sure they'd work fine.

Re: Disappointing image quality, especially for chroma keying
 

Please give it a try!

Re: Disappointing image quality, especially for chroma keying
 

Tell you what, Dominik... When I get around to shooting something on chroma screen with the camera, I'll try to remember to post something here to show you how well it works with the FS700. In the meanwhile, I don't feel too compelled to convince you, since you sound pretty sure of yourself on your opinion of the camera.

In the meanwhile, you should try to be more careful about who you quote haphazardly on the forum!

Re: Disappointing image quality, especially for chroma keying
 

I shoot this on my FS700 with the stock lens Screen grabs from Sony Vegas 11 it was not lite very well.

Re: Disappointing image quality, especially for chroma keying
 

If I wouldn't be convinced after all the tests I've done, it would have to be due to a serious personality disorder of mine.
I want to show other people my observations to give them a chance not to do the same mistake as I did, making a decision based on wrong assumptions as nobody on the Internet tested this use case, but many are saying "I'm sure, it will key fine!".

Re: Disappointing image quality, especially for chroma keying
 

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Re: Disappointing image quality, especially for chroma keying
 

How can you quantify sensor and processing issues when the image being projected on the sensor by the optics is of poor quality? The images are not even in focus, the creases on the cloth appear to be in better focus than the people. . Thats like using an SD monitor to evaluate HD resolution.
I agree that the chroma resolution from the FS700 is lower than would be expected from the PMW200 or a similar well designed 3 chip camera, but what I see in your test images falls well short of the performance I get from mine, but this looks to be mostly down to poor studio setup and focus. You might also want to consider dropping your exposure of the green a bit too and doing something with your lighting to provide better separation from the foreground to the background. It is over exposed and the green is very washed out and spilling all over the place. The green should not be at exactly the same exposure level as the foreground skin tones, that makes pulling a decent key tough with any camera.

Re: Disappointing image quality, especially for chroma keying
 

Very true, but putting an SD lens on an HD camera will limit the quality of the output to no better than SD. The camera will never perform better than the lens, use a poor lens or optical system and you will get poor results.

Re: Disappointing image quality, especially for chroma keying
 

Here's a little test I did last year. The Alex on the left is the internal 4:2:0 recording using CG3, the Alex on the right is from what I recorded on my PIX220. This isn't a real shoot, just us larking around to see what we could break. FWIW, the FCPX chromakey settings are near-as-dammit identical (as it should be).

At the time, the FS700 was very, very new - I think there's a little bit of sharpening in the Picture Profile, which tends to add a thin black line round your edges, which 'eroding' the key does not fix in a nice way.

Is this the sort of key (nay, the sort of rushes) I'd expect to see on a pro shoot? NO! It was the sort of test that would show up where we'd have to spare more time (like a proper picture profile). Was it an easy key in FCPX? Hmmm - ask me another.

Am I happy with the FS700 for Chromakey? Compared to the FS100, hell yes. Compared to the EX1? Not really happy, I'd pick the EX1 over the FS100, and might even pick it over the FS700 if I had good lighting. Awful truth? The chromakeying software has a lot to play. I don't like the FCPX keyer, but my clients lack the budget to do a good job in After Effects.

Re: Disappointing image quality, especially for chroma keying
 

Was that interlaced Matt?

Re: Disappointing image quality, especially for chroma keying
 

I've watched this thread, but only now looked at the samples you provided Dominik... wow...

Please pay attention to Alisters comments re lighting and spill - THAT is where a lot of your problem is... garbage in, garbage out.

I'm a novice with green screen, but I could see in just a glance the glaring problems with your SETUP that you are (wrongly!) trying to blame on the camera. I know enough to look at your samples and see you've got green "spill" everywhere, and some seriously weird things going on with something else I'm not sure of (what the heck is causing the HORRIBLE jagged edge on the right side of the dress in your first sample???).


Getting a clean key is not as simple as hanging a green cloth, and pointing a camera at the subject and expecting the equipment to turn straw into gold. And then acting with surprise and criticism when you have the same straw you started with??

FWIW, being critical of others getting acceptable results when they are trying to help, when anyone who knows a little about this technique can spot the problems with your setup, is not really indicative of you wnating to SOLVE the problem, but rather wanting to demonize a camera when there are other things to be addressed.

There is much to learn here on DVi, but nothing to be learned if you've made up your mind and don't want to consider wise advice...

Re: Disappointing image quality, especially for chroma keying
 

I find that chroma keying in Final Cut or Premiere Pro to be a waste of time. At best it looks like a local TV weather cast segment.
Compositing is best done in After Effects.
Here is a great tutorial dealing with less than perfect keys courtesy of Andrew Kramer VIDEO COPILOT | After Effects Tutorials, Plug-ins and Stock Footage for Post Production Professionals
I think that everything in this tutorial was shot on the 7D so we're not talking about 4:4:4 colorspace.
The key you can get with this technique is pretty amazing and can really save the day and doesn't take too much time.

enjoy,
KG

Re: Disappointing image quality, especially for chroma keying
 

The Ultra Key effect in Premiere Pro is particularly good, and with CUDA acceleration, it's a render-free option, which results in huge efficiency when you're dealing with lots of footage.

With proper lighting, any camera can produce very good results for most applications.

Re: Disappointing image quality, especially for chroma keying
 

Quite badly lit. Green spill everywhere. The camera does not light the scene for you, nor does it tell you how to get a proper greenscreen. Get some distance to the actor and the greenscreen, and light them separately.

Composition also seems to be quite "not done". Keylight needs some work, it won't magically do stuff for you. Ofcourse the leg will show through, it's completely full of green spill!

Ultrakey in Premiere is also...not very good. Except for speed. There are really no one button solutions. Primatte for Fusion is pretty nice.

Re: Disappointing image quality, especially for chroma keying
 

Dominik, have you shot that in SloMo?

Re: Disappointing image quality, especially for chroma keying
 

I agree the lighting and proximity of the talent to the green screen is far from ideal for a good key. I also agree there is a focus problem. There seems to be some comments which indicate the software doing the keying is a major factor. I believe its much more of the above. If everything is done correctly (yes of course that's a big if) FCPX will key extremely well without any adjustments at all. In fact, that is quite a clue you have done your setup correctly. I have read there have been folk doing tests with green screen work using 4.2.2 vs 4.2.0 and the results were not as substantial as expected. In some cases the result was marginal and the 4.2.2 introduced much more noise which caused additional problems. Finally, a hint I read about and worked well for me is to reduce any sharpness/detail settings to as low as possible. You can sharpen quite a bit in post after you have gotten the key.

Re: Disappointing image quality, especially for chroma keying
 

Hey guys, I've read all your posts and it's been helpful. I have a green screen shoot coming up and since most of you have already shot greenscreen footage with the FS700, what technical advice can you give?

Which would be the best picture profile to use?

Re: Disappointing image quality, especially for chroma keying
 

I'd recommend using the picture profile that will provide the best gamma match to the background plate - that makes the foreground (person) look the way you want them.
Just don't deviate too far from the norm on your matrix settings. I wouldn't recommend trying it with an S-Log type profile.
Realistically, if the green is properly lit it will probably all fall around 52-55 IRE, and in that range it will not be overly effected by the PP selection, so just make sure your foreground looks right and the lighting is perfect.

On the hardware side, I would think that if you had the latest firmware upgrade and an ext recorder and could do it in 4k that would be amazing...

Re: Disappointing image quality, especially for chroma keying
 

I found green screen keying on this a breeze (rotoscoped the rest with edge define) all done in after effects CC

Re: Disappointing image quality, especially for chroma keying
 

Some basic tips for lighting chroma key setups, rehashing what some other folks have already said, but condensing it into a quick list...

1) Even lighting on the screen - flooded lights or broad sources are best (LEDs can work well. So do Kinos)
2) Expose the screen at around 50 IRE. If you have a histogram on your camera, that means "mountains in the middle."
3) Get a good amount of distance between the back of your subject and the chroma screen. This prevents green (or blue, depending on your screen) reflection "spill" on your subject. But, it also helps to isolate your lighting. Dedicate separate lights for the screen and for the subject. Control of your key light spill is pretty important, since it's likely to cause one part of the chroma screen to receive more than another, which serves to damage the uniformity of the color you're going for. With added distance from the key, the screen gets less unwanted light spill due to fall off.
4) Expose skin tones around 70-75 IRE, with whites going up around 95 IRE.
5) A nice back light on your subject for added edge refinement, being careful not to shine it on your lens

Re: Disappointing image quality, especially for chroma keying
 

Hi

My 2c.

Keep the subject as far away from the screen as possible .... Ie you need as big a screen as possible.

Make sure the screen is true chroma green ( paint or fabric or paper). Buy the best. Don't eyeball it!

Light the screen separately from the subject ... Put chroma green gels over the light sources.

Don't white balance using a white card near the green screen set!!!!!! green spill will ruin everything!

expose for the screen ( 60 -70 % ) then light the subject as required. If you have to err... Go over on the subject. You can bring it down in post.

Back light the subject.!

Getting the floor to key right is hard

Try the keyer in FCPX ... It is really killer.