Ed has a brief explanation about 'Zoom Burst' in his tutorials.

This is an effect that can be achieved by manually zooming the lens while keeping the shutter open.

I went to my friend's wedding a little while ago and tried it on her, I found out that you need a steady hand for this, otherwise you get a lot of undesired movement while trying to zoom. Even with this minor detail, it turned out to be a lot simpler that I thougth, with just a few tests I was able to get at least 2 usable frames.

But then I read this tutorial (it was actually for Light Room) about how to achieve this in post production, therefore I decided to try it in The Gimp and add a new trick to my portfolio. And guess what? It was a lot easier than I expected!!

The first image is I got with The Gimp in post production, the second one is what I got by manually zooming the lens, and this is what you do:

1. Load the image of course!
2. Duplicate the base layer (only if you follow the optional part)
3. Select again the base image and go to: Filters->Blur->Motion Blur Here you choose 'Zoom'
Then you are presented with a few options, but the one that you will play with is 'Length'
In this image I used '15', play around and find your magic number.

Optional (The idea with this optional steps is to bring back the clear sharp image that you had at first)
4. Select the duplicated layer and move so that it will be on top of the modified one.
Make a selection of the center of attention (in this case bride and groom), you can do it with the ellipse selection tool or free select or what ever you want, it is up to you.
5. Go to Select->Feather and use a number close to 15
6. go to Select->Invert and then Edit->Clear or 'delete' in your keyboard. This will delete all but your center of attention.
7. Reduce the opacity of this layer to a number close to 50, I used 62% for my image.

After this, you can merge the layers or just export it as jpeg, gif, tiff, png ... you name it.

Well, it is very simple, 2 steps actually!

Let me know how it goes and post your own tests if you want.

Regards,
Felipe

Be the change you want to see in the world
-- Mahatma Gandhi