Target painters can be useful if the opposition is 'sig tanking'. This means they have specifically selected ships and modules with low sig-radius in order to make them harder to hit. 'AHAC Gangs' (Zealot HACs fitted with afterburners and armor plates supported by Guardian logistics ships) are examples of sig tankers.
Like most EWAR, target painters are stacking penalized.
Target painters increase the signature radius of a target by a certain percentage. The two benefits of this are increased damage and decreased targeting time.
Missile weapons have an explosion radius; if the target's signature radius is less than the explosion radius, the damage done to the target will be reduced. Target painters allow larger missiles to apply more damage (up to their theoretical maximum) against smaller targets.
For turret weapons, a ship with a larger signature radius is easier to hit. This translates into higher damage done to that target.
This dps boost applies for every ship firing at the painted ship, assuming those ships are not already doing maximum theoretical damage. So for large ships shooting at medium targets, this can be a significant damage increase across the entire fleet.
If target painters are your only EWAR, then you want a T1 ship like the Vigil or Bellicose. T2 versions are no more effective than T1 for TPs, cost a lot more, and require more skills for literally no benefit over T1, covert cloaky Rapier excepting. However, the T2 versions are the Hyena EAF, Rapier Force Recon, and the Huginn Combat Recon.
Target Painters are still somewhat effective on unbonused hulls. So if you have a ship with a spare mid slot and think you might be shooting at under-sized opponents, a target painter might be a good choice. They are popular choices on stealth bombers and other torpedo ships like the Raven.
Since the point of the target painter is to increase applied damage, painting anything except the primary or secondary target is useless. Also, painting a target that is a size-class larger than the weapons systems being used is often pointless, as those weapons will most likely already be applying full damage.
There are no modules that increase target painter performance.
Particle Dispersion Projectors - increase optimal range of Electronic Warfare modules. This rig has decreased shields as a drawback.
Note: The Target Painting drones experience stacking penalties, rendering a flight of them inferior even compared to an unbonused T1 Target Painter. Avoid using the TP drones where possible, and try to fit a target painter to your ship (or anyone else's ships if they are flying with you).
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