Do a set using a weight you can lift for 8-15 reps.
Then perform a set of lying (supine) front raises using a weight you can do for 8-15 reps.
The point of maximal mechanical tension when doing front raises is when your arm is parallel to the floor. So when doing the seated raises, the point of max tension is when your arms are perpendicular to your torso. With the lying front raises, the point of max tension is when your arms are parallel to your torso.
I'll have to admit that my mind was elsewhere. We were all sitting in the lounge at the Los Angeles Strength Seminar and everyone was drinking wonderful things like beer and bourbon, often together. One lovely young woman was drinking a wine spritzer. I can allow that, if you're a lovely young woman.