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class="style5" 24p and Moire

>Published : 10th June 2005

>Do patterns moray (sp) moree easier/quicker when shooting in 24p than in 60i?

Warren Gentry


class="Paragraph">Moire

>What camera system are you using? Moire is an alias and is resolution dependent(inversely)

>Michael Bravin
Chief Technology Officer
Band Pro Film & Digital


class="style7">> Moire

class="style7">> What camera system are you using? Moire is an alias and is resolution >dependent(inversely)

>Moire, thanks!

>Footage was shot on a DVX-100. I'm hoping 24p will look cleaner on a SDX-900.

>Warren Gentry


class="style7">>Moire, thanks!

>>Footage was shot on a DVX-100. I'm hoping 24p will look cleaner on a >SDX-900.

Or it could look worse. Moire can be more apparent in a system with more resolution than one that is a little soft. It's an old tv news trick -- defocus slightly to make the herringbone jacket stop buzzing. Or zoom back slightly, so the pattern isn't resolved.

>I can't think of any difference 24 P would make in Moire patterns. Moire will show up on stills.

>Steven Bradford
Collins College
Phoenix Arizona


>Warren Gentry writes :

class="style7">>Footage was shot on a DVX-100. I'm hoping 24p will look cleaner on a >SDX-900.

>If both cameras are shooting the same video standard (in terms of scan lines, not fps) they'll produce similar moire patterns when shooting i.e., herringbone tweeds, knits, distant cyclone fences, and other fine, regular patterns.

>The camera with the higher resolution is likely to look worse, however, so I'd test both of them, and/or maybe back off on sharpness settings as much as you can get away with.

>If your moire is confined to a small part of the frame and the shot is static, you can probably get away with selectively defocusing the moire area in post. I've done this successfully with herringbone jackets on talking heads.

>Dan Drasin
Producer/DP
Marin County, CA


class="style7">>If both cameras are shooting the same video standard (in terms of scan >lines, not fps) they'll produce similar moire patterns

>I'm thinking the 24p camera is going to see a lot less moire.

>Art Adams, DP [film|hidef|video]
Mountain View, California
San Francisco Bay Area - "Silicon Valley"


>Michael Bravin wrote:

class="style7">> Moire

>I think Warren is interested in Eels. Electric Eels.

>Jeff Kreines


>Art Adams writes :

class="style7">>I'm thinking the 24p camera is going to see a lot less moire.

>I don't think the frame rate per se should affect moire very much. . .But interlaced cameras tend to mix both fields to some extent (to reduce twitter) so their vertical definition differs from that of an otherwise identical progressive camera. This difference would either increase or decrease the moire effect, depending on the orientation and spatial frequency of the original pattern.

>My 2c worth, but I'd welcome other views on this...

>Dan "less is moire" Drasin
Producer/DP
Marin County, CA


class="style7">>I don't think the frame rate per se should affect moire very much.

>The "p" in 24p should help eliminate some moire. Same with 30p and all the other p's.

>Art Adams, DP [film|hidef|video]
Mountain View, California
San Francisco Bay Area - "Silicon Valley"


>Another way to decrease moire in any camera that allows you to do it is to back off on the enhancement or sharpness circuits a bit.

>Steven Bradford
Collins College
Phoenix Arizona


>Dan wrote:

class="style7">>The camera with the higher resolution is likely to look worse, however, >so I'd test both of them, and/or maybe back off on sharpness settings >as much as you can get away with.

>I could be wrong here, but in my experience the opposite is true. I saw a DSR-500 and a consumer camera, shooting the same narrow striped jacket and I remember the 500 looking far cleaner.

>Think about sharpness charts, the higher the resolution the more accurate the reproduction. The lower the resolution the more ringing in the moire.

>Illya Friedman
Production Account Executive
Wexler Video
Burbank, CA


>Before we get too carried away in this discussion : Let us remember : Moire is an NTSC only artefact. You'll only see it in downconverts, not in native HD, (or native SD, or native Y,R,B analog component Beta playback.)

>Also: readers have been debating about whether apparent sharpness increases or decreases Moire : Ahhhhh, that's a "Yes/No" : Turning down detail definitely decreases moire artefacts. One reader wrote in asking why then, do low res (cheap) cameras have more moire?

>The reason I would guess, is that inexpensive cameras, and (downconverters) don't have sophisticated enough filtering to adequately remove cross-color artefacts. (When we started doing low def down-convert telecasts side-by-by side of HD TV trucks, we had tremendous moire artefacts until we started taking digital feeds from the HD trucks, and stopped taking NTSC downconverts from inexpensive downconverters.)

>Lew Comenetz
Video Engineer.