if you liked the look of the new and improved finale, you can thank Zack Snyder for lighting a fire underneath his VFX team, thanks to what’s been dubbed as the “Hallelujah” trailer that kicked off the last leg in Zack Snyder’s Justice League’s road to existence. I learned this firsthand as I spoke with the film’s VFX supervisor, Bryan Hirota, a member of Scanline VFX. While that first trailer was a blessing for the fans, it cause a slight bit of concern for the team at Scanline, as Hirota revealed in the following story:
Article source: https://www.cinemablend.com/news/2567391/zack-snyders-first-justice-league-trailer-helped-vfx-artists-perfect-the-flash-look-snyder-cut