6-8 hrs. or more

A would say 6 - 8hours also.

Tomatoes need limited amount of light (in lumin )
The amount of lumins can come either from INTENSE direct sunshine or indirect daylight.
So any direct sun beyond plants needs for photosynthesis is not going to make any positive contribution and the plant juts would try to cope with that. Tomatoes in particular are NOT full sun (all day sun) plants. I have personally grown tomatoes with 5 to 7 hours direct sun with no problem. People down south, (TX , FL, S.CA ) use shade cloth to reduce the intensity and thereby lumins.

Depending on weather (mostly humidity)....morning sun is really quite important. The more direct sunlight the better. I do container plantings...so guess where I move my maters?