Damage increased by light

How much of an increase in damage does light do? In-game it says

Light increases your level, increasing the damage your abilities deal against higher-level enemies

but I would like to know the specific increase.

Solution 1:

First off, leveling up will not increase your gun's damage unless you're already experiencing downscaling due to being underlevelled, but it does increase ability damage (as the description says). I just did some testing to see how level affects the damage of your abilities (which Destiny takes to mean super, grenade and melee skill). I tested with my Gunslinger, using throwing knife and Golden Gun against level 20 Fallen Shanks (by going to a level 20 version of story mission).

This level was chosen because it's not above any of the levels I'll test (unlike 24) and still are not far enough down that you'll get level scaling from being too high (refer to note about scaling at the end).

The results are here, with level given as Level(Light amount) as given by the number next to the progress bar when hovering over light level:

  LvL  | Melee | Super
-------+-------+-------
 27(96)|  615  | 2153
 27(89)|  590  | 2063
 25(71)|  529  | 1849
 23(49)|  462  | 1617

So as you can tell, ability damage does scale with light level. One surprising aspect of this, which I only noticed because I equipped the wrong legendary armor (Queen's gear... you know how it is), is that it's not your level that determines damage, but your total amount of light. This means that every time you apply a defense upgrade (which gives you a little bit of extra light), your abilities power up slightly too. Neat!

This increase seems to be linear, and with my skills (throwing knife and golden gun) the increase per unit of light is 3.2 damage for melee and 11.2 for super.

In addition, I did a minor test to see if level difference has any effect on damage, by going to the 24 version of the same mission, and throwing some knives around. Results:

  LvL  | Dmg 
-------+-----
 27(96)| 615 
 27(89)| 590 
 25(71)| 529 
 23(49)| 315

Here you can see that the only difference is that level scaling was applied when we were underleveled. As for how damage scaling in relation to level differences works, I'll copy paste my comment on another answer in this question here:

Damage scaling occurs if the enemy is above your level (the drop off is more like 30% per level, ending up with "Immune" at 4 levels difference, when enemies become ??s), or the enemy is more than 9 level below your weapon's "internal level", when you start losing about 5% damage per level. "Internal level" seems to be defined as the weapon's level requirement until for whites and greens, but has an added bonus for blues and legendaries. My purple "requires 20" acts like it's level 27

In addition, I'll note that for the purposes of ability damage, it counts as having the same "internal level" as you.