I assume you mean half loads and full loads when you're talking about "Hollywood Blanks" and more realistic ones. Anyways, there is a big difference between the muzzle flash of blanks and real ammo, as this video beautifully demonstrates.
YouTube - Muzzle Flash. Real Rounds vs. Blanks
As you can see, a lot more unburned powder is thrown into the air from the blanks, causing a big fireball and much more light.
Although I've never shot my Mosin at night, I have seen it make fireballs about the same size with the same ammo used in that video...
Not to derail this, but it depends. Some blanks are loaded with different and often faster burning powder so that they can create the same pressure to cycle a semi / fully automatic gun.