Yes, we do allow upgrades. The way it works is you would receive 50% of the value you have already paid to go towards the upgrade.
For Example: If Luke paid $100 for a 2K collection, the 4K version of the collection is $300. Luke would pay $250 to upgrade his collection to the 4K version.
If you have any further questions regarding this, or would like to upgrade your resolution, please contact our sales team at Sales@ActionVFX.com.