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DOF Issues with Canon 6D

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Ashley Ripka
DOF Issues with Canon 6D
on Apr 2, 2015 at 1:38:27 pm

So we were shooting in a studio against a blue screen with 2 Canon 6Ds. These were the setups/settings.

Camera 1 (6D)
Lens: Canon 50mm F/1.8
Shutter: 125
f stop: 4.0
ISO: 800

Camera 2 (6D)
Lens: Tamron 28-75mm F/2.8
Shutter: 125
f stop: 4.0
ISO: 800

Here is a photo of our lighting setup. We're just trying to figure out why our DOF is so shallow, and then even while we're shooting and uploading footage, we're getting a weird "dancing" effect on the edges of our subject so we're not getting a clean key.




Any help would be appreciated. Thank you.


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Warren Eig
Re: DOF Issues with Canon 6D
on Apr 2, 2015 at 3:20:06 pm

The blue screen should be at about Key or ½ stop less. Try a smaller aperture. ƒ8 or 11.

Any difference?

Warren Eig
O 310-470-0905


email: warren@babyboompictures.com
website: http://www.BabyBoomPictures.com


REEL: http://www.babyboompictures.com/BabyBoomPictures/Reels.html


For Camera Accessories - Monitors and Batteries
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Ashley Ripka
Re: DOF Issues with Canon 6D
on Apr 2, 2015 at 3:24:39 pm

Nope. We even went outside up to an f stop of 22 and we're still getting these dancing lines when we key. The focus still looks extremely shallow through the lens too.

Is this just an issue with the 6D?


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Warren Eig
Re: DOF Issues with Canon 6D
on Apr 2, 2015 at 3:32:11 pm

Have you tried lowering the ISO. Also what is the reading on the Blue screen. What is the reading on the subject?

Warren Eig
O 310-470-0905


email: warren@babyboompictures.com
website: http://www.BabyBoomPictures.com


REEL: http://www.babyboompictures.com/BabyBoomPictures/Reels.html


For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com



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Ashley Ripka
Re: DOF Issues with Canon 6D
on Apr 6, 2015 at 1:11:18 pm

Thank you for the suggestions. We're going to look into purchasing a better camera, but we need this to work for now.

We had a hunch it was the camera, but we were just hoping that there was a way around this.


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Blaise Douros
Re: DOF Issues with Canon 6D
on Apr 3, 2015 at 7:35:09 pm

When you're looking through the lens, it's usually at the lens' widest aperture--the camera stops down to the actual setting when you either set it to Video mode or fire a picture.

See my other reply for more info.


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Blaise Douros
Re: DOF Issues with Canon 6D
on Apr 3, 2015 at 7:31:33 pm
Last Edited By Blaise Douros on Apr 3, 2015 at 7:42:57 pm

What is your camera-to-subject distance? At f4, you won't have much DOF to play with, especially if your subject is standing closer to your camera (DOF decreases as lens-to-subject distance decreases). You might consider, if it's a short distance, switching to a longer lens and moving your camera further from your subject.

I'm assuming you're shooting 1/125th to avoid motion blur in the footage? If it's just an interview standup, consider going to a 180 degree shutter (1/60th or 1/50th depending on shutter speed) and increasing f-stops. This gives you extra DOF and will eliminate any soft edges where your subject might be blending into your BG.

Shooting Canon 6D is unfortunately asking for a bad time when pulling a key. The color information in the 4:2:0 8-bit codec is really insufficient to pull a good key. I would also suggest (if you have access) using a green screen. I have a hunch that the Bayer compression is negatively affecting the colors present in your footage--there are many more green photosites on your sensor than there are blue, which means that the blue pixels are being interpolated by the compression algorithm...possibly resulting in the blue dancing effect.

After Effects has a lot of tools for cleaning up keys--if you don't have the option to re-shoot, then a pass through AE is going to be your next step.


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Ryan Holmes
Re: DOF Issues with Canon 6D
on Apr 4, 2015 at 9:44:29 pm

Ashley - I think Blaise's advice is extremely sound:

(1) Shoot at a 180 degree shutter angle (basically take your frame rate and double it, that's where you should set your shutter speed.
(2) Any Canon DSLR is bad, bad choice for blue/green screen because of the 4:2:0 8-bit h.264 codec it employs. You may have better luck with a green screen as the physical sensor inside the camera is more sensitive to that color over blue. However, you're still dealing with a heavily compressed codec and one that doesn't do well in visual fx or color grading.
(3) DOF is an entirely different problem and is really more of a math equation than anything else. There are plenty of online DOF Calculators for you to explore:
http://www.dofmaster.com/dofjs.html
http://dofsimulator.net/en/
http://www.cambridgeincolour.com/tutorials/dof-calculator.htm
http://www.outsight.com/hyperfocal.html
So practically speaking, this helps you get an idea of how close or far you should put your subject to your camera in order to achieve a desired background look (in focus or out of focus). The DOF may play into your ability to pull a key since your focus plane may be so small it's hard to get a clean edge. Add to that the above listed problem of a poor h.264 codec with poor chroma sampling and your in a world of hurt.

Hopefully this helps point you in a direction that solves your problem. Ultimately, I would recommend a camera that is more geared explicitly towards video (a Canon 6D is decidedly nowhere near this ideal). Something more like Blackmagic Pocket/Cinema/Production cameras, Sony FS700. FS7, Canon C100, C300, etc would all serve your blue screen needs better than a Canon DSLR, IMHO.

Ryan Holmes
http://www.ryanholmes.me
@CutColorPost


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Warren Eig
Re: DOF Issues with Canon 6D
on Apr 6, 2015 at 2:24:50 pm

One other option is installing Magic Lantern firmware if you are still running Canon firmware 1.1.3.

You can find ML firmware here: https://builds.magiclantern.fm/#/

It will allow you to shoot 14 Bit RAW so no compression in a 4:4:4 color space. It basically shoots cinemaDNG that needs to be processed before you can do anything with it. I've used it very successfully on my 5D Mark III.

Warren Eig
O 310-470-0905


email: warren@babyboompictures.com
website: http://www.BabyBoomPictures.com


REEL: http://www.babyboompictures.com/BabyBoomPictures/Reels.html


For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com



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