More Moire issues

[christina voros]

just shot a short on the red and noticed some heavy moiring issues - shooting on a studio set we had several flat wooden doors, painted with matte paint, in shades of gray or grayish green that suffered serious moiring (when they opened especially). We'd been shooting under tungsten lights and when we first noticed the issue I added an 80d filter which seemed to make it better.

BUt the next day we were using daylight balanced units and the same thing happened this time on a blue door. The effect seemed less apparent in RedSpace than when viewing it in Raw or Rec709 - but i am looking for advice both in what would be causing this and how to minimize its presence while bringing the footage through post....

any help greatly appreciated

thanks,

cv

 

[NateWeaver]

I'm trying to figure out how a flat matte painted door would cause "moire"?

Is it possible the word you're looking for is "banding" or "noise"?

 

[Dan Hudgins]

kookaloris

kookaloris

If you are getting banding from the compression, using a "kookaloris" on the lighting (point source) may help, if you break up the light the compression uses more bandwidth on that area of the frame.

Can you post a link to a 16bit (48bpp) TIF file from the footage straght out of REDCINE with REDLOG and no CC?

 

[Leon V]

We have never seen moire either.
The only moments are, when shooting 4K close on a LCD monitor, the grid interferes with the grid of the sensor.

The work-around there turned out to be, to switch to 2K. The moire is much less in 2K compared to 4K.
Maybe switching to 2K works in your situation also. I it is a real moire, where fine structures interfere with the sensor grid.

succes,
Leon

BLD AV Media

 

[David Mullen ASC]

It doesn't sound like Christina means "moire", which is an interference pattern that comes from fine lines in grid patterns interacting with the grid pattern of the photosites on the sensor, though it's important to realize that some moire also appears due to fine line patterns in the shot interacting with the grid pattern on the monitor and the moire (aliasing) may not be in the recording. And certainly an 80A filter would have no affect on moire, unless it caused you to open up two f-stops and thus threw more of the offending grid pattern out of focus.

 

[christina voros]

perhaps it is banding? its my first time working with the camera and thats the term that was being thrown about by my AC....it looks like some kind of compression or artifact - the pool of light falling on the door that was soft to the eye appeared as noisy concentric circles when the door moved. The light levels were on the lower end of the spectrum (shooting at a high 2.8 with the meter rated at 320) but is that really dark enough to be causing noise, especially when using daylight balanced fixtures?

the issue seemed less pronounced when viewing the footage on the laptop on set - (which i imagine isn't really a reference anyway) and almost non existent in redspace - I haven't had a chance to sit down with the footage at a proper HD monitor yet to really see what i'm looking at though - and being my first time with the post workflow, not sure if there is something i can do to diminish the effect as the clips are brought into post

 

[David Mullen ASC]

Yes, that sounds like banding, some sort of quantization error. It probably isn't in the RAW files though. I'd get some footage converted at full resolution and check.

The 720P monitor output (and I believe the QT proxies too) is not a full debayering so some artifacts appear that are not in the originals.

 

[christina voros]

thanks so much david - much appreciated!

 

[martinnoweck]

as for as i know all the real time outputs (red lcd, red evf, hd-sdi) and quicktime proxies perform live debayering, so banding will be an issue in the preview.

another point where banding can occur is when converting red material to 8-bit Video.

last but not least banding can also be a problem resutling of the viewing device - if your monitor or your laptop screen only has 8bit resolution or less there could be banding.

kind regards,
martin