The important answers needed
a. What version of Premiere Elements and what computer operating system is involved, including 32 or 64 bit?
b. What are the pixel dimensions of the photos that you are using, and how many of them are there?
c. How much of this project has video as well as photos and what are the properties of the videos (video compression, frame size, frame rate, interlaced or progressive frame rate? Are you willing to accept black borders for your images?
Based on the answers to the above, I will offer you a customized workflow based on the details that you supply.
Add On...What is your intended output for this Timeline content?
Thanks for getting back to me. It is Premiere Elements 13. Windows 7. The pixel dimensions vary, and there may be 50 or so when I am done. Most of the project is still images, and I am not sure about the video questions. I am using a canon xa 20. When I do projects with no still images I don’t seem to have a problem.
Providing no compromises to the performance of the program, my generalized reply would be to set the project's project set to match the properties of the video source and then import the photos as is, and scale them as necessary for best fit into the Edit area monitor's space established by the project preset. If compromises, then crop/resize photo before import into this project.
I have gone into great details on the suggested "do not exceed photo pixel dimensions" recommendations that you see online.
Please consider, and then we can discuss this further as it applies to your specific situation.
Add On: Based on your camera video information, I would assume that you should have 1920 x 1080 project settings and a 1920 x 1080 space in the Edit area monitor to fill. To be detailed next after your review of the situation.