4:3 source going to a 16:9 projector
our existing 4:3 song slides (1024x768)


The real resolution of a slide depends on the program and file format they are in. If the slides are in PowerPoint or similar, they have no native resolution, they have a proportion.

If they are JPG files or a video, yes, you are stuck with the resolution.

A projector has indeed a native resolution, if it is a 16:9 of good quality it could be full HD 1920x1080 or simply HD 1280x720px, in some cases 1366x768px.

A JPG of 1024x768 will be resampled but I really doubt this would be an issue. In any case it is better to store the slides as a real slide, and not as a "photo".



Regarding if a projector will "projet bars" depends on the model and on the graphics card of the computer sending the data. Most likely the computer will also send a 16:9 signal, and the bars will be given by the application, not by either the computer or the projector.

But if your computer sends an old SD signal, the projector might squish or squash the image.