[Enhanced Senses] Darkness, Night Vision, and flickering

[Anaraxes]

Originally Posted by zoncxs

I cannot find anywhere in my copy of Enhanced Senses any mention of flickering lights. Can you provide a page reference?

Enhanced Senses p 13, in the Illumination Levels box. Inline in the second half of first paragraph.

Originally Posted by Strabo

1. GURPS Powers: Enhanced Senses says that torch is equivalent to an illumination level of -1. In Basic Set, it is -3, in Template Toolkit 2: Races it is -2, in DF it is 0. Enhanced Senses, however, mentions that flickering lights add another -1 to -3. Is this flickering penalty taken into account in the table?

The text seems clear enough (emphasis mine).

Originally Posted by Enhanced Senses p13

{The illumination table} assumes steady illumination; flickering lights or moving shadows can add another ‑1 to ‑3

So, yes, add a flickering penalty to a torch, should that torch be flickering. (As a properly atmospheric low-tech dungeon fantasy torch ought! :) But not all flames flicker.)

One reason there are new rules for illumination in Enhanced Senses is that the existing examples in early 4e works are simply not consistent. Those early sources weren't examples derived from this set of rules, unpublished but known to SJG authors; this set of rules was worked out afterward, matching the existing rules as nearly as possible, and just ignoring the outliers where necessary. It's nice that this example works out, but don't expect every existing reference in other rules to line up exactly. (I tried, once, while looking at Anthony's house rules for illumination, which were similar to the ones that appeared in Enhanced Senses.)

+10 to Vision rolls to notice the lighted area (p. B358). However, they’re at ‑7 to see anything else.”
This causes many questions, especially when multiple light sources are visible, and Night Vision is present.

This one I also find confusing as written. I have some thoughts, but I'll need to think a bit and put them into shape.

However, from your diagram, I'd say that the +10 to spot a light source is for just the light source itself, not everything within its illuminated radius. All those objects already have a light level that gives the penalty to spot them. It's easy to spot the torch, even a long way away. That doesn't make it equally easy to see everything around the torch; that's what illumination levels are for.

The -7 for outside observers looking in is the confusing part to me.

The penalties really ought to be a sliding scale based on the illumination level differences between observer and subject. They seem to be assuming everything not illuminated is at -10 (unlike the ambient illumination in your diagram), and that the observer is at that illumination.

3. “Prolonged exposure to intense light can cause lasting or permanent vision loss.” How long is prolonged?

Depends on the intensity of the light and its wavelengths, as well as repetition. Lasers can be fractions of a second. Direct sunlight -- staring at the sun -- can be seconds to minutes. Reflected sunlight from waves or UV exposure can be accumulated over days, months, or years -- the sort of thing that might be better reflected as a kind of Cyclic damage that accumulates vision penalties rather than HP damage, or an additional effect added to aging rolls. Focus -- the amount of area the light affects -- also matters; those lasers can easily burn spots on your retina, even when they seem like they're "low" powered just from the electrical consumption. And a human eye is much, much smaller than the square meter used in the definition of lux and lumen. That 500 milliwatt Class 4 laser spot is a tiny fraction of a square meter, all on the retina, whereas the 100 W lightbulb is throwing out energy in all directions, most of which isn't even visible light. This one's probably up to GM call.

Here's more than anyone wants to know on the topic. Turning that into gameable rules might be difficult.

[Anthony]

For those who are curious about the forum brouhaha, that's https://forums.sjgames.com/showthread.php?t=132662

[whswhs]

Originally Posted by Anaraxes

The -7 for outside observers looking in is the confusing part to me.

The -7 is for the case where you've looked at a flashlight, or a campfire, or a torch, and your eyes have adapted to that light level, and now you turn and look into the darkness and you can't see anything, because your eyes haven't adjusted.

[Anthony]

Also, the listed brightness for a torch is at 1 yard; subtract 1 for 2 yards (actual effective distance will rarely be less than 2 yards, because the light source is usually held more than a yard above the ground). I originally gave brightness at 2 yards because of that. Penalty will routinely be -3 or worse in real situations because of distance.

[Anaraxes]

Originally Posted by whswhs

The -7 is for the case where you've looked at a flashlight, or a campfire, or a torch, and your eyes have adapted to that light

Makes sense. Much like my guess about spotting something else in the dark while looking at the light from a distance. (Hm, I deleted that, didn't I? At least that served the purpose of not further muddying the waters.)

How about a time to readjust? A few seconds, just in my personal experience. Or maybe the penalty fades one point per second, if someone's will to track that. Matters in combat, but negligible when you've got time.

[whswhs]

Originally Posted by Anaraxes

Makes sense. Much like my guess about spotting something else in the dark while looking at the light from a distance. (Hm, I deleted that, didn't I? At least that served the purpose of not further muddying the waters.)

How about a time to readjust? A few seconds, just in my personal experience. Or maybe the penalty fades one point per second, if someone's will to track that. Matters in combat, but negligible when you've got time.

My experience is that it takes minutes, not seconds.

[Anthony]

Originally Posted by Anaraxes

How about a time to readjust? A few seconds, just in my personal experience. Or maybe the penalty fades one point per second, if someone's will to track that. Matters in combat, but negligible when you've got time.

It says in the box '2 minutes per -1'. Fast adaptation to changing illumination is mostly between levels that would both be considered 'no penalty' in GURPS (e.g. your typical 'come in from bright sun into a house interior' is dropping from something like 100,000 lux to 1,000).

[Anaraxes]

Originally Posted by whswhs

My experience is that it takes minutes, not seconds.

Originally Posted by Anthony

It says in the box '2 minutes per -1'.

So it does. That's a reasonable time for cone response. I had in mind the pupillary response, with perhaps the first point or so of the cone adaptation, two or maybe three levels of penalty. I don't have to wait for four minutes to be able to see after crossing from street lights to a normally lit residential room, or when stepping from a dim-to-normal room into a hall with no lights before becoming able to make out the stairs well enough that it's not dangerous to go down them.

[Anthony]

Originally Posted by Anaraxes

So it does. That's a reasonable time for cone response. I had in mind the pupillary response, with perhaps the first point or so of the cone adaptation, two or maybe three levels of penalty. I don't have to wait for four minutes to be able to see after crossing from street lights to a normally lit residential room, or when stepping from a dim-to-normal room into a hall with no lights before becoming able to make out the stairs well enough that it's not dangerous to go down them.

Pupillary response is limited to the equivalent of about 1 level, and mostly doesn't apply in situations where GURPS would assign darkness penalties in the first place because your pupils are fully distended even at the brighter level of illumination. The examples I can see of for rapid adaptation are mostly either "to bright to have darkness modifiers in the first place", such as sunlight to indoors, or "simple enough that it doesn't actually matter that your vision isn't entirely adapted".

[Strabo]

Originally Posted by Anaraxes

However, from your diagram, I'd say that the +10 to spot a light source is for just the light source itself, not everything within its illuminated radius. All those objects already have a light level that gives the penalty to spot them. It's easy to spot the torch, even a long way away. That doesn't make it equally easy to see everything around the torch; that's what illumination levels are for.

That makes sense to me, even if it contradicts the rule (which says "lighted area").

Originally Posted by whswhs

The -7 is for the case where you've looked at a flashlight, or a campfire, or a torch, and your eyes have adapted to that light level, and now you turn and look into the darkness and you can't see anything, because your eyes haven't adjusted.

Thank you, that answers one of the most confusing questions of mine.

Now, the only major question is the G-H situation on the diagram. It seems that G would be unable to see H despite being adjacent, and the different between the light levels being merely -1, while H would be able to see and attack G at -4.