A proper black tie dress is not something you wear very often which means it needs to work hard when you do. These are midi length dresses in satin and silk that read as intentional and elegant without trying too hard. The fabric drape matters enormously. Good satin catches light without looking cheap and silk moves with you instead of against you. The silhouette tends toward simple because that is what actually looks expensive. You are looking at clean lines and strategic necklines and possibly a back detail that justifies the front simplicity. These are the black tie dresses that make you feel like yourself just elevated.