Office building, fully glazed
Floor-to-ceiling venetian blinds across the whole façade of an office building. Inside, the view stays; outside, the heat stays.
Keep the light, not the heat
Floor-to-ceiling glazing brings in heat nobody ordered for the summer. Slats solve that differently from a curtain: they tilt. Set correctly, they take the direct sun out of the room and keep the daylight. Artificial light at midday is the sign that the shading is set too coarsely.
Why on the outside
External shading catches the heat before it comes through the glass. Internal shading lets it in and then holds it there. That is the whole reason an office façade is fitted on the outside, even though it is the more demanding way.