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Sony NXCAM NEX-FS700 CineAlta
4K EXMOR sensor with SDI, slow-motion recording.


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Old February 21st, 2013, 08:35 AM   #16
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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.
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Old February 21st, 2013, 09:53 AM   #17
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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.
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Old February 21st, 2013, 11:23 AM   #18
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Re: Disappointing image quality, especially for chroma keying

Quote:
Originally Posted by Eric Darling View Post
Chromatic aberration is determined solely by glass. It's a byproduct of the qualities of a lens, not an image sensor.
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)
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Old February 21st, 2013, 11:29 AM   #19
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Re: Disappointing image quality, especially for chroma keying

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Originally Posted by Eric Darling View Post
I can and have got great Chroma keys with EXcams and the FS700/C100.
The C100 is much better than the FS700 in terms of resolution. Can you give examples of chroma keys you did with the FS700?
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Old February 21st, 2013, 05:17 PM   #20
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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.
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Old February 21st, 2013, 11:01 PM   #21
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Re: Disappointing image quality, especially for chroma keying

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Originally Posted by Eric Darling View Post
Misquoted... I actually haven't tried any chroma keys with the FS700, though I'm sure they'd work fine.
Please give it a try!
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Old February 21st, 2013, 11:08 PM   #22
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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!
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Old February 21st, 2013, 11:36 PM   #23
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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.
Attached Thumbnails
Disappointing image quality, especially for chroma keying-image7.jpg   Disappointing image quality, especially for chroma keying-image6.jpg  

Disappointing image quality, especially for chroma keying-image5.jpg   Disappointing image quality, especially for chroma keying-image4.jpg  

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Old February 21st, 2013, 11:41 PM   #24
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Re: Disappointing image quality, especially for chroma keying

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Originally Posted by Eric Darling View Post
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.
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!".
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Old February 22nd, 2013, 12:48 AM   #25
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Re: Disappointing image quality, especially for chroma keying

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Old February 22nd, 2013, 02:50 AM   #26
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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.
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Old February 22nd, 2013, 03:18 AM   #27
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Re: Disappointing image quality, especially for chroma keying

Quote:
Originally Posted by Dominik Seibold View Post
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)
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.
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Old February 22nd, 2013, 12:20 PM   #28
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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.
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Disappointing image quality, especially for chroma keying-chromakey_fs700.jpg   Disappointing image quality, especially for chroma keying-chromakey_fs700_raw.png  

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Last edited by Matt Davis; February 22nd, 2013 at 12:33 PM. Reason: (added uncompressed raw image)
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Old February 23rd, 2013, 01:38 PM   #29
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Re: Disappointing image quality, especially for chroma keying

Was that interlaced Matt?
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Old February 23rd, 2013, 02:34 PM   #30
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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...
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