In the Chronicle of Darkness book, there's a Tilt and Condition for being blind. What about for varying levels of darkness - is there a way to gradient the penalty that anyone knows of, or would you have to make up a rule for, say, a creature with infrared vision?
There's no real guidance in 2e core on vision penalties that I can find. It does mention vision penalties exist, and provides a way to nullify them:
Night Vision Goggles
Die Bonus +2, Durability 1, Size 2, Structure 1, Availability ••
Effect: Night vision goggles amplify low-light condi- tions, allowing characters to see when they otherwise could not. A character with night vision goggles does not suffer penalties for acting blind. Bright lights can render the wearer temporarily blinded, as if he had a flashlight shone in his eyes.
Also worth comparing, for figuring out what base mortal capabilities are supposed to be, is Vampire: The Requiem 2e. It also has rules about ignoring vision penalties, though it also doesn't explain what they would otherwise be for mere humans:
Kindred do not suffer normal vision penalties for being in the dark, and can compensate with hearing. In full darkness, they only suffer a –2 die penalty to rolls that require vision.
So you can infer that whatever mortal vision penalties are, they're noticeably worse than -2 in full darkness. It also gave similar rules for their owl nemeses, the Strix.
The Strix have even greater affinity with darkness than the Kindred and can see unimpeded without any light. An Owl suffers no dice penalties due to poor visibility even in complete darkness. If a Strix does have sufficient light for a human to see by (moonlight, or streetlights, for example), it enjoys a +3 die bonus to rolls involving perception and sight.
So monsters that can see in the dark in general, infrared or not, just have no penalties or reduced penalties, rather than having a +3 bonus or something. Even the Strix only has its own bonus in a case where there wouldn't be any vision penalties at all, it has none in the dark.
Now in 1e, it did give specific example penalties for when it was dark when describing Perception and Larceny. Both were -3, and there was nothing detailed like a gradient of degrees of darkness or anything.
Possible Penalties: Dark (-3), obscuring weather (-1 to -3), subtle detail (-1), obscure detail (-3), distracting circumstances (-1 to -3)
Possible Penalties: Lack of tools (-1 to -5), darkness (-3), someone approaching (-2)
And there was an entire section about "Fighting Blind," which applied when trying to fight in pitch darkness. The player had to both correctly guess the direction to shoot/punch correctly, and then succeed in rolling a chance die (no matter how large your dice pool would be if you could see).
The Storyteller knows where the target actually is, and secretly makes a chance roll (see p. 125) for you if your character attacks in approximately the right direc- tion.
Then the equipment section mentions possible negative penalties "depending on the degree of darkness" when fighting by flashlight.
Durability 1, Size 1, Structure 2, Cost n/a
Function: Unlike most tools, flashlights don’t offer dice bonuses. They simply diminish the effects of dark- ness, reducing the penalties of “Fighting Blind” (p. 166). Using a flashlight while performing actions makes the feats possible, but still challenging. Rather than be reduced to a Storyteller-controlled chance roll, you are still able to make your own rolls, only at a penalty of -3 or -4 depend- ing on the degree of darkness. So, if your character tries to shoot a target by flashlight, and he has 2 Dexterity, 3 Fire- arms and a gun rated 3, your dice pool might be composed of four dice (2 + 3 + 3 - 4).
Alternatively, the Storyteller might decree that per- forming a task in the dark imposes a standard penalty of - 3 and having a flashlight diminishes that penalty to -2.
No Resource dots are required to be able to afford a flashlight.
There are no specific rules about varying levels of darkness. However, you can use the generic "Circumstances and Equipment" section of the core book (page 69).
The core book says that most of the time, the penalty from circumstances (which includes poor visibility) should be between -1 and -3. In rare cases (perhaps supernatural darkness), the penalty can be -4 or -5.
Similarly, a bonus from infrared vision should not be higher than +3 unless it is exceptional in some way.