January 31, 2005

8:46 AM

VideoFilter: When I take stills from a DV capture and use them in my Premiere Footage as a slide, sometimes they image will shake, as if the image is quickly switching back and forth between frames. What causes this and is there any way to cure it?
posted by bryanzera to (5 comments total)

Load the frame into Photoshop and select the "Deinterlace" filter.

Basically, if you have a moving object, it will appear in a different place in the odd and even fields. When output as a still, the odd and even fields are alternated, causing the shake. The solution is to use the same image for the odd and even fields, which is what the deinterlace filter does.

(or maybe it's just a bug in Premiere, I don't know)
posted by cillit bang at 8:55 AM on January 31, 2005

Alternatively, if your camcorder supports a progressive mode, use that when shooting footage that'll be used for this purpose.
posted by kindall at 9:01 AM on January 31, 2005

Deinterlace is your friend.
posted by brownpau at 9:08 AM on January 31, 2005

I agree with all the deinterlacing suggestions. There's another issue (related to interlacing) that can cause flicker: horizonal lines. You should avoid very thin horizontal lines when working with video. This includes anything with stripes and also text with really thin elements (like a font in which the letter T is topped with a one-pixel high horizontal line).

A TV displays one-halve of the image first, skipping every other line. Then it goes back and fills in the blank lines. These two passes are called fields, as in the upper field is displayed first, followed by the lower field (some systems reverse this field order, displaying the lower field first). TV (in the US and Japan) show approximately 60 of these fields per second. If you have elements with one-pixel high lines, those lines will be in one field but not in another. So they will flicker on and off.

If someone gives you an image with lines like this and you must use it, try running a blur effect on it. Just blur it slightly so that the lines are smudged down a pixel or two.
posted by grumblebee at 10:55 AM on January 31, 2005

For interlace flicker of the sort grumblebee mentions, blur only vertically if you can. In Photoshop you can do this with a convolution kernel (Filter>Other>Custom). It's only a hunch, but I bet Premiere has a similar filter.
posted by kindall at 11:53 AM on January 31, 2005