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DSLR Color Flicker Problem

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Daniel Owens
DSLR Color Flicker Problem
on Apr 5, 2011 at 2:21:52 pm

Does anyone know what may be the cause of this DSLR color flicker issue? This was shot with a T2i and a Canon 17-55 lens. The focal length was at 17mm for this shot. I did have a Hoya Super Multicoated filter on the front. No ND filter was used. I was using a glidetrack to track slowly towards the church. I am noticing a color flicker around the top edge frames of the door. It's almost like the lens or camera are confused as to which color to stick with (flickering from brown to black.) Anyone know what is going on? I noticed when the camera stopped moving, the flicker stopped as well. It has something to do with the movement of the glidetrack and the camera/ lens. Is this normal? See the link below: You need to make the image full screen to see what I am talking about around the door frame mostly.Your feedback is much appreciated.

http://gallery.me.com/lifetimestudios#100015

Thanks so much


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Jason Jenkins
Re: DSLR Color Flicker Problem
on Apr 5, 2011 at 2:47:55 pm

Looks like a moiré issue to me.

Jason Jenkins
Flowmotion Media
Video production... with style!


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Daniel Owens
Re: DSLR Color Flicker Problem
on Apr 5, 2011 at 3:37:30 pm

Thanks Jason. So you don't think it is a defect in the lens right?


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Jason Jenkins
Re: DSLR Color Flicker Problem
on Apr 5, 2011 at 5:19:58 pm

DSLR's, in general, have problems with moiré and that's what it looks like to me, so no it's not your lens.

Jason Jenkins
Flowmotion Media
Video production... with style!


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Phil Balsdon
Re: DSLR Color Flicker Problem
on Apr 5, 2011 at 9:25:17 pm

Moire problem, something you have to aware of with DSLR video. Most commonly occurs on fine line detail such as your example. It's caused by the need to "line shed" pixels and reduce the frame pixel size to 1920 x 1080.

Try the DSLR Moire filter here; http://colorbyjorg.wordpress.com/plugins/

Be careful not to apply it with too high settings it may affect the colour balance of the whole image.

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Jason Jenkins
Re: DSLR Color Flicker Problem
on Apr 5, 2011 at 10:51:33 pm

[Phil Balsdon] "Moire problem, something you have to aware of with DSLR video. Most commonly occurs on fine line detail such as your example. It's caused by the need to "line shed" pixels and reduce the frame pixel size to 1920 x 1080.

Try the DSLR Moire filter here; http://colorbyjorg.wordpress.com/plugins/

Be careful not to apply it with too high settings it may affect the colour balance of the whole image."


Or... you can just shoot with the Panasonic GH2 :)

Jason Jenkins
Flowmotion Media
Video production... with style!


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Peter Burger
Re: DSLR Color Flicker Problem
on Apr 6, 2011 at 9:25:16 am

Most people would agree to reduce the internal camera sharpening of your Canon to absolute minimum to reduce moiré a bit. You can reintroduce sharpness (if at all needed) in post.


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Casey Petersen
Re: DSLR Color Flicker Problem
on Apr 7, 2011 at 9:44:36 pm

Hey Peter,

How would you recommend reintroducing sharpness in post? I have Final Cut Pro. Just wondering how you do it, and what settings you use.

Thanks!



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Peter Burger
Re: DSLR Color Flicker Problem
on Apr 8, 2011 at 7:59:46 am

Hi, Casey!

The way DSLR cameras reduce picture size from those huge image-sensors to comparatively small HD size is by skipping information, which raises or even creates artifacts like moiré. Letting the camera sharpen those pictures internally, boosts these problems by raising local contrast (darkening dark edges and brightening bright edges).

So dialing the sharpening down, will help to reduce picture artifacts.

Reintrudcing sharpness is just as easy as applying a sharpness filter in post. Some guys (myself included) rather use the "unsharp mask" filter than "sharpness", since it gives you more possibilities to fine-tune, but that's just a matter of personal taste.

Sharpness filters in an NLE do the same thing as the ones inside your camera, but you can adjust the intensity to your needs and likings or even use masks to apply the sharpness to parts of the image.

Hope this helps!


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Casey Petersen
Re: DSLR Color Flicker Problem
on Apr 8, 2011 at 2:42:21 pm

I've never used the unsharp mask before...must be the name! Looks very interesting, and I think it would look better than the plain sharpen filter.

What kind of "typical" settings do you use with it....the base settings you use that work on most clips without having to customize it?

Thanks!
Casey



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Peter Burger
Re: DSLR Color Flicker Problem
on Apr 8, 2011 at 3:25:12 pm

Well, it depends largely on the picture... I don't think there's a perfect setting that works with most footage.

I don't work with FCP, so I don't know the FCP default settings, but starting with the defaults and playing around with threshold and radius might give you good results.

My approach is as follows:

Unsharp mask has three sliders: strenght, radius and threshold.

When using that filter, first step for me is to set the strenght very high (default in Premiere is 50%, so I set it to about 150% or even higher), just to see more clearly, which parts of the picture are affected by the settings.

Threshold defines, "when" the filter attacks, in terms of "how dark or bright must a pixel be to be affected". Lower values create more extreme results.

Radius defines how "far" the darkening or brightening goes. Higher values create more extreme results.

After tweaking threshold and radius, I reduce the strenght back to what looks good to me (something between 20%-50% in many cases).

So, you can create very subtle effects or even very extreme effects with halos and stuff...

Hope this helps!


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Kristian Albrigtsen
Re: DSLR Color Flicker Problem
on Apr 7, 2011 at 3:38:01 pm

I dont mean to steal this thread, but i have a related issue (i think).

I shot this TL fully manually with the Nikon D7000, Nikkor 10-24mm lens, f/10, shutter 1/160. Shot in raw, batch processed with capture NX to TIFF, imported as sequence in AE and exported uncompressed, then compressed to h264 with QT.

Any ideas regarding the reason for color/brightness flicker in this timelapse?



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Phil Balsdon
Re: DSLR Color Flicker Problem
on Apr 7, 2011 at 10:28:35 pm

Kristian, your problem is not moire.

Your problem looks like something to do with exposure or changing light from frame to frame as the whole picture frame is changing in brightness.

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Kristian Albrigtsen
Re: DSLR Color Flicker Problem
on Apr 8, 2011 at 5:43:17 am

Im new to DSLR timelapse and now understand that the flicker issues is related to small variations in apperture when shooting the sequence.

I downloaded GBDeflicker Trial and applied it to the allready exported file just to test, and must say im relatively happy with the result (default settings in GBDeflicker). Although i would like to solve this before PP (have read that longer shutter/ND filter perhaps can decrease the variations in apperture)

Thanks!



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Richard Harrington
Re: DSLR Color Flicker Problem
on Apr 8, 2011 at 2:54:06 pm

Must shoot 100% manual

Richard M. Harrington, PMP

Author: From Still to Motion, Video Made on a Mac, Photoshop for Video, Understanding Adobe Photoshop, Final Cut Studio On the Spot and Motion Graphics with Adobe Creative Suite 5 Studio Techniques


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