How to use slow motion with SLR camera

Are you talking about slow motion video? The video slow motion effect is also called the upscaling effect. If your SLR supports video shooting at 100 (for example) frames per second, and you use video software to set playback at 25 or 30 frames per second later, you will be able to see the upscaling effect more clearly. If the camera itself does not support shooting high-speed video, it can be achieved later through the infinite speed plug-in in PR.