remove black bars at either side of frame

There are no bars. The viewer at the moment is just wider than the frame.

If you playback this in fullscreen, there will be bars - not because they are in the video (they're not!), but because of the aspect ratio. It does not matter if you scale the image up. Your project is 4:3. That is what will play. Scaling the images will only change what you see inside the same rectangle.

Having "bars" is inevitable, because your mac screen is 16:10 or 16:9, depending on model, and your video is 4:3. The extra empty space will typically appear as black.

This is a blue rectangle (4:3) fitting inside a red (16:9) rectangle.

Black bars are there because your images have 4:3 aspect ratio and your project is 16:9.

You can set your project to a custom size in 4:3 aspect ratio, or you can change the Spatial Conform of the images from Fit to Fill.

The images will er... Fill the frame (cropping a bit off from the top and bottom).

Tom is of course correct.

There are not black bars in the project itself. It is just that the size of the viewer is larger than the video.

You can confirm that easily. Go to Preferences->Playback and change the Player Background to White (or Checkerboard).

If the images did not fill the frame, you'd see white on the sides. But you don't, do you?

I just said that as an example in a 4:3 aspect ratio.

There are not many options in 4:3.

I don’t think that being a big wall means you need a higher resolution than say watching on a tv. The bigger screen mean bigger pixels, but also that people will sit farther away. Just like you sit farther away from your tv than from your laptop.

My 50” HD tv has fewer pixels than my 16” MBP, and it’s fine...

The size of the wall isn't important, assume your projector is powerful enough. All that matters is that it's the same 4:3 aspect ratio.

If you want to change Spatial Conform, just select all the images in the timeline and go to the Inspector:

Not the transform tool. The viewer itself. Let's go back. What are your project properties/ 4000x3000 or something else?

I'm talking about this

If you made the project 4000x300 they should fit exactly. You might have to make a custom project. Or what Luis said.

Tom, you're right - I did not see that the project was already 4000x3000. As you say, the images should fit exactly...