How to avoid Moire Effects (jiggered still pictures) using iM and iDVD.

Question

This is a discussion going on forever and forever in this forum. I had the problem of bad looking slideshows myself, and I am hearing the same tips over and over again that just don't work. This is what I found out on how to avoid moire effects in your still images, when you want to edit a slideshow using iMovie - and I personally think, this explanation makes a lot of sense.
Try it on your own and you will have had the last bad looking still image slidehow on the TV screen ever!! Here we go:
Like everybody here I am talking about the process of creating a slideshow incuding movie strips in iMovie to get as a final result a DVD with menus and such using iDVD.
And the common problem with stills and iMovie 5.02 are the so called jiggered pictures iMovie creates. Call it a moire effect, if you'd like.
Whenever full resolution still images are importet from iPhoto into iMovie, the quality that iMovie will spit out in the end is disgusting. Period. Just disgusting.
It has nothing to do with that iMovie does not display it properly on the Monitor or we are just in preview mode - the results are bad there and will be bad (maybe even worse) on the TV screen.
There is no SIGNIFICANT difference between wether the pictures are imported with KB on or off, whether they are imported as still frames or as video clips using iMovie "import" function. iMovie can treat the color fairly bad, overprocesses the pictures and - worst of all, the moiree effects you will see in the endresult are just very very bad. It is worse when the pictures are panning a lot (KB).. This is true for every picture containing a lot of detail (Trees, Forests, horizontol lines (stairs) etc.) - not so bad for closeup face shots, unless that person is really old
There is no SIGNIFICANT difference on the result by how the iMovie project is fed into iDVD. When the movie is sent to iDVD using the iM command "send to..." the quality is worse (and you let iM render when it asks) than if the movie is dragged into the iDVD window - but again, the difference is not significant. The result will suck. The DVD will also look bad, when the iMovie is exported has high res quicktime first, before imported into iDVD. Again, its slightly better that way, but not significant.
Whenever a slideshow is created in iPhoto and than exported to iDVD (or via being a quicktime movie through iMovie into iDVD) the result will be however stunning. But that totally defeats the purpose of iMovie and the degree of freedom of designing slidehows in a very appealing manner.....
The problem I think lies in how iMovie processes still images. And this is not a bug, but more of a mathematical/programmatical problem. iMovie has to REDUCE THE RESOLUTION of your still. A 2000x3000 pixel image @ 300 dpi(roughly the dimensions of a 6 MP image) has to be downsized to a TV image (NTSC or PAL, whichever) which has a resolution of approximately 480x640. HD is accordingly higher. The amount of pixels has to be reduced. iMovie can do that. NOT GOOD. But it can. The problem starts when the picture is panning around (KB). iMovie makes a let us say 5 second movie @ 30 fps out of one still image. Almost every frame will be slightly different from the previous one due to the used KB effect. So, the routine of iMovie does this downsize calculation for each single frame - and it removes each time different pixels from the still image, due to a slightly different source still image. Got it?
Now, when you look on how moiree effects occur (which is some weired math in it's own) than it makes sense, that we see all this jiggereing in horizontol lines of high res. patterns.
I found that if I reduce the size of each image in Photoshop (or Photoshop Elements) prior to importing it into iMovie, the quality of the final product that iMovie and subsequently iDVD spits out in the end is AMAZING (reduce the dpi to approx. 72, so the image resolution is roughly 480x640). This is not a difficult process, because both programms (PS and PSE) handle BATCH PROCESSING. Just let the Mac work for a couple of hours or so.... its WORTH IT (and don't forget to make copies of the high res originals beforehand... :D).
(before you resize, find out about how to properly resize and rescale an image!!!!)
I am slightly annoyed that I found that out after producing a long long long long and really good slightshow, that is watchable but looks REALLY cheasy and cheap).
I hope this helps out.
Waenni
Mini G4   Mac OS X (10.4.8)  

Answer 1

I agree that iMovie's still image quality is embarassingly bad and has many bugs.
Even with no Ken Burns, the sharp images tend to flicker on a TV because iMovie doesn't blur them properly.
And as you very well described, iMovie's Ken Burns produces uneasy zooms/pans because the subpixel rendering is, uh, suboptimal.
iMovie's immortal rendering bug when exporting non-Ken Burns'ed images to iDVD/tape doesn't make things any better.
Yes, bicubically downsampling the input images to 640x480 or adding gaussian blur to the megapixel input images takes care of the flicker and uneasy zooms/pans, but as a side-effect the maximal zoom-ins are then TOO blurry.
The best workaround is to use Photo To Movie's higher quality export setting. It has the best quality rendering engine (I recently compared it to Still Life and FotoMagico). Disclaimer: I'm just a satisfied customer of Photo To Movie.
See also:
http://www.sjoki.uta.fi/~shmhav/SVCDon_aMacintosh.html#slideshow