I'm using a bunch of photos in a piece I'm making. I find myself often using the whole photo, then following it up with a zoom in on a detail and some slow panning.

This is an open-ended question: any advice for this? I'm not struggling with it, I'm wondering what, if anything, I want to keep in mind when doing the Ken Burns effect with some photos? I wonder if there is a detail or two I might not be aware of. Would i want to move in a particular way or direction? I dont know what unknown unknowns exist with this.

I've done this a bit. I don't know if any of my advice will help but I look at a few different things when I decide exactly what I'm going to do with a picture. First, is what is the best effect for that particular picture. Some are more effective zoomed in, some zoomed out, some panned, some panned and zoomed (in or out), some very little motion, and the speed at which any of these effects are done. Then I look at how well the effect blends with the pictures before and after it, and with the piece as a whole - not too much repetition, etc. If I'm set on a particular effect for a certain picture, but it doesn't balance well with the pictures around it, I may move it to another place. Then, you have to consider how the picture and effect fit in with the music.

In the end, you're trying to enhance the emotional impact of the video using these effects. You need to do this without bringing too much attention to the effects themselves, just the feelings they create. It needs to be subtle. In other words, it's not a formula, it's something you need to do by feel. I find the more connection, I, personally, have with the piece or subject, the better job I do at making the effects work well for others.

I spent 4 years as the senior editor at a company that did among other things, custom "slide shows" and movies. Most were based on photos so we had to come up with some creative ways of treating them. I have so many tricks it would be hard to list...here's a few...

Don't forget "rotate". A little can go a long way with some zoom in or out. As mentioned, type of effect depends on the pic. Portrait pics are a bit of work. What I usually do is put an enlarged version of the pic in B&W and blurred as the background. I hate leaving black space. Some other tricks are layering a couple of similar pics and having them move differently. Page peels or cube spins actually work well to remove the pair and reveal the next photo.
By far my fav effect we dubbed "seperation anxiety". With the right photo, you can pull the subject out in photoshop and paint in the background. Put the two layers in Motion and pull the subject forward in the z axis. Apply a camera and then when you pan or zoom it appears to be a 3d pic! There were two other editors and we used to have contests to see who could pull the most layers to make the 3d effect even more insane. I pulled 5 layers in one pic (foreground plants, subject, background plants, sky and a river flowing) and the customer commented saying they didn't remember shooting video! Key was not to alter the pic. Had to remain true.

Last comment is make sure to vary the speed of the effect from pic to pic. If say over a 4 sec period, make some move 10%, others 20% and so on. We timed all our pieces to music and tried to hit lyrics with appropriate pics. All depends on subject. When the stars aligned, it was quite a way to present photos!

Robert,

Quick follow up question: You wrote, "What I usually do is put an enlarged version of the pic in B&W and blurred as the background. I hate leaving black space."

So, do you have an example of this you can point to? I'm trying to visualize it. I'm thinking of ways to fill up space and this seems like an option, but I cant imagine how having a photograph against itself doesnt look really weird.

Another easy effect is to throw in candles on a birthday cake or rising smoke from a cigarette.
Really easy in Motion with round-tripping.
I've even thrown in a waterfall effect on some photos that had the opportunity.
The key is quick treatment. Most slideshows don't have the budget for a 15-30 minute treatment of a photo onscreen for 5 seconds.
Photoshop is really efficient for cutting the subject out and blurring the background to help the eye find the important elements. Once you get the process down you can roundtrip in 1-2 minutes.
I usually just cut the subject, output a png and create the effect in the NLE . . . such as gradually blur the background, maybe have the background recede a bit, as well.

I second the rotation suggestion . . . it doesn't require much. Sometimes the straight pan or zoom creates horizontal line skipping or 'patterns' that are disrupted by a bit of rotation.
Also, easing in and out of motion is useful. But this can monkey with the path.

Robert,

Quick follow up question: You wrote, "What I usually do is put an enlarged version of the pic in B&W and blurred as the background. I hate leaving black space."

So, do you have an example of this you can point to? I'm trying to visualize it. I'm thinking of ways to fill up space and this seems like an option, but I cant imagine how having a photograph against itself doesnt look really weird.

I will have to dig one out. It's been a few years and they are on my backup drives.
Maybe further description will suffice.
Imagine a full body portrait pic...place that off to one side and scaled to fit completely within the viewing area. Then put a zoomed in on the face version behind it and to the opposite side. Blur it a little, make b&W and darken a bit.
Drop shadow the color top layer and do a very subtle rotate and scale.

Another cool trick is if there's two people in the pic full body. You keep the color full pic in the middle and split the closeup on the faces to either side.

Hope this helps!