If you have 80 slides for a 45 minute seminar you are in trouble. Use a Powerpoint-projector presentation whenever possible. This allows you to incorporate last-minute changes. If you prefer slides , make sure to have the slides MADE one week before the seminar date. Be careful with the colors that you use for slides.
Colors often look very different on the computer screen as compared to the projected image.
This often results in illegible slides because the writing does not stand out over the background. Always combine a light color with a dark color. For example, yellow writing works well with dark blue backgrounds. It is difficult to see anything on a dark fluorescence micrograph if it is on a bright white background. Use a black or dark blue background instead.