removing moire effect in pan/crop?

billcoffin wrote on 6/10/2004, 11:55 AM

I've been using pan/crop to zoom into a jpg image. I get an ugly moire effect, especially on diagonal lines. MS tech support suggested pre-rendering using the highest-quality settings. I've also experimented with adding motion blur but the choices here are not well-documented. (Gaussian? or Pyramid? Assymetric?)

One solution is to add a blur to the original jpg. Then I get the ugly effect only later in the zoom. (I'm zooming out.) So a solution would be to set up a series of jpg images and string together back-to-back zooms on differently-blurred jpgs. But this would be a ton of work.

If I can't find a solution, I'll have to wrtie off the pan/crop feature as useless, at least for creating the "Ken Burns" effect on stills.

Comments

dand9959 wrote on 6/10/2004, 12:30 PM

One problem might be the size/resolution of the jpg image you are zooming.
Regardless of how far you zoom in, the rendered image will always be 720x480. So, if you start with, say, a 600x400 image, and zoom in 50%, MS will render the (zoomed) 300x200 image into a 720x480 space, resulting in very ugly stuff.

Steve Grisetti wrote on 6/10/2004, 2:32 PM

Also note that JPEGs make moire effects. That's the nature of their compression process -- and the more you compress the worse it gets.

Best is to figure how much you plan to zoom and then use an image (JPEGs are fine, as long as you don't use too low a resolution) that allows for it.

In other words, if you plan to zoom in to 50% of the photo, you'll need a photo that's at least 1310 x 960 so that, once you zoom in, you still have a 655 x 480 image on your screen.

Don't over-res it either. Make your photo too high a resolution and you may bog down the software by having to work with more data than you need.

Just start at the end of your zoom and calculate the resolution you'll need from there.

dand9959 wrote on 6/10/2004, 3:09 PM

I find that 300dpi is a good resolution to use, if possible.