DSLR Hair Moire Questions

A

Andrew J. Allsbury

Well-known member
Ladies & Gentlemen,

I recently drank the DSLR coolaid. I purchased a t2i for still images and instantly fell in love with its video capabilities, over the past few weeks I have used the t2i on several small projects and really have hit only one major snag (not major enough to become un-excited, but major) and that is hair moire! I shoot a lot of docu. style interviews for webisodes...promos...etc and recently have been running into rainbow colored hair (on head) moire constantly! Up until this point I have attacked the problem in post by using channel blur, gaussian blur, black diffusion, down rez to 720, etc. BUT having been in video for about 10 years and having worked through complete nightmares (like 35mm adapters) several times I would imagine that there are things that can be done during production to lessen these problems (angles, exposure, lighting, focus, etc). What has been everyone else's experiences and what are your suggestions??

Thank you!
 
Are you shooting in a progressive mode and where are you judging the images?- i.e. on an HD monitor or your computer screen?

Noah
 
1080p30, and it is very noticeable on my big 1080 hd computer monitor...less noticeable on everyone else's monitors and my 42in 720p television.
 
Welcome to DSLRs. Some folks will never see the issues, others see them every single time.

Here's the thing with moire: if something is in sharp focus, it's going to alias. Period. No escape. Depending on what frequency it hits at, you may or may not get moire. The more that's in pinpoint focus, the more potential for moire that there is.

What can you do about it? Lots of things, most of them counterintuitive, but all revolve around blur. The only fix for moire is blur. Moire happens when the image is too sharp for the sensor to properly resolve, so you have to blur it down.

So -- get that hair softened down out of focus. Use a diffusion filter on the lens. Open up the iris more to narrow down the DOF and put some of the hair out of focus. Use a Caprock anti-moire filter. Shoot at f/22 so diffraction blurs your image just enough. Use a cheap lens that doesn't resolve as much...

The irritating thing about moire is that it comes and goes, it all depends on how the fine detail pattern lines up with the sensor pixels. It won't always be there. Aliasing will be, but moire only exhibits itself when a repeating pattern lines up with the sensor pixels JUST RIGHT. Take a look at Chris Santucci's video which shows the problem in an easily-understandable way.
http://www.youtube.com/watch?v=Lgw90AYbaYMhttp://www.youtube.com/watch?v=Lgw90AYbaYMhttp://www.youtube.com/watch?v=Lgw90AYbaYMhttp://www.youtube.com/watch?v=Lgw90AYbaYMhttp://www.youtube.com/watch?v=Lgw90AYbaYM
 
They may not like you linking to a competitor forum :)

Maybe just get rid of that link and post the info instead. I think the gist of it is that you can open the file as a .mov in photoshop cs3 and use noise filter - reduce colour noise, and then export the file.
 
before doing anything else, first make sure you are stting the sharpness setting on the T2i all the way down to zero.
 
Thanks for the input guys...I think you are actually supposed to link to the forum because I have seen guys get in trouble on other forums for copy/pasting as it is a copyright infringement.
 
Well…like I’ve said I’ve yet to see the moiré in hair detail (maybe because everyone I’ve filmed so far has darker hair)….but I have seen it on fabrics. Now…with hair what I do see at times is aliasing.

I do notice however that the times I have a problem with moiré or aliasing is when I use Canon lens and not my third party Pentax lens. The Pentax lens are nice and sharp but I don’t see the aliasing and moiré like I do when I use my 18-55mm Canon AF lens. I wonder why that is?
 
not as sharp?

Ever since Kholi made a post in some thread about the moire he see's in peoples eybrows, now it haunts me like the plague. I see it everywhere and every time, so disappointing.
 
Well I'm experimenting with some lowlight stuff but I'm having trouble rendering out to video. I left it on all night and although photoshop was running and using up half my resources, I couldn't tell if it was making any progress. Anyone have any experience working with this?
 
And when I bring the PSD into premiere cs4 and try to export out it gives me this error:

- Source File: C:\Users\RYANDD~1\AppData\Local\Temp\Uhn Tiss_3.prproj
- Output File: C:\Users\Ryand Davis\Desktop\Exports\720 60p_4.mpg
- Preset Used: Custom
- Video: NTSC, 1280x720, 59.94 [fps], Progressive, Quality 5.0
- Audio: 384 [kbps], 48 kHz, 16 bit, Stereo, MPEG
- Bitrate: VBR, 1 Pass, Min 4.00, Target 10.00, Max 18.50 [Mbps]
- Encoding Time: 00:00:00
5/8/2010 1:40:42 PM : Encoding Failed
----------------------------------------------------------------------------------------------------
Invalid combination of framesize/framerate/profile/level. Please recheck the settings and try again.
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