Is it a good idea to use lighting mods with mods that add new locations?

Question

I really like the look of Antique Dragon enb and Caffeine enb. Even if I could run them with my new ram though, they both require ELFX. I'm afraid that could mess with the lighting of mods that add new locations (including most quest mods, new lands mods, houses, dungeons, you get the idea).

I do recall having lighting issues with Magical College of Winterhold. I think it had something to do with the lighting setup I had at the time. Of course, I was installing running both Vivid Weathers and RLO along with any enb that took my fancy without knowing that VW and RLO aren't compatible with each other, or even with most enbs. I'm far more careful now, but still.

Is a lighting mod really such a good idea? I always liked the more dramatic lighting that RLO gave that no weather mod could pull off for some reason. I know ELFX has quite a few patches, but honestly I don't know what they do.

Is it fine to run lighting mods along side mods that add new locations? I know ELFX in particular has to add light sources to vanilla locations to keep things from being too dark. This makes me worried that it may make mod locations too dark that don't have a patch for it.

Answer 1

Lighting in Skyrim is complicated. There are three separate components that matter:

1. Your choice of ENB (or community shaders, if using that instead of ENB).
2. The "base object" settings for each light source (as well as some other base object settings such as image spaces etc.).
3. The placement and configuration of light sources in each cell.

(1) and (2) are "global" in the sense that, for the most part, they will always affect every location in the game equally. (2) is a bit of an edge case in its own right, because in theory, a mod could introduce new custom light sources that are not affected by the rest of your load order, but in practice, most mods don't do this since the vanilla light sources already cover most reasonable use cases. (3) is per-cell. If the rest of your load order contains no edits of type (3), then that means it does not require edits of type (3) in order to achieve the desired effect, so it should be compatible with most vanilla-like mods (i.e. mods that use lighting in a similar way to vanilla).

Edits of type (3) appear in xEdit as Cell edits (or to be pedantically correct, as edits to the references in each cell). In practice, most "realistic" lighting overhauls require edits of type (3) to achieve their desired effect, because Bethesda simply did not place very many fine-grained light sources in most vanilla cells. If a mod advertises that it, for example, "add[s] lights to all light sources and remov[es] any light without a source" as ELFX does, then it almost certainly uses edits of type (3), and so any modded location which does not have an ELFX patch will probably not match the desired aesthetic.

Having said all of that, this is not necessarily the end of the world. The most common problem, if a cell has the wrong lighting, is for that cell to be too bright or too dark. The "correct" brightness is somewhat subjective, and the degree of the effect varies depending on exactly what combination of mods you have installed (i.e. on exactly what your load order has done with (1) and (2)). I would recommend making a hard save, trying out your desired mod, and testing it to see how bad it really looks. You may find that it is more tolerable than you would expect (or maybe not, depending on your load order and personal tolerance for these sorts of deviations). I would tend to expect that the problem will be more significant for overhauls which are intended to make dungeons and nights very dark, or which severely reduce ambient light (to eliminate vanilla's characteristic Hollywood darkness), but the only way to know for sure is to try it and see.

If it is a popular mod, it may also be useful to look in the "requirements" tab on Nexus under "Mods requiring this file." If someone has made an ELFX patch for the mod in question, then it will almost always appear in that list. As discussed, proper brightness can be subjective, so patches of this nature are inherently opinionated. The fact that a patch exists does not necessarily imply that it will produce the best possible lighting by your personal standards - again, you have to try it and see.

Answer 2

First of all, please read through the mods' descriptions—a lot of the information you seem to be looking for can be found there. For example, mod authors might tell you they used a specific lighting mod while creating and tweaking their creation, and recommend using that same mod. But it will also give you an idea of what a mod changes, and how, and if there are incompatibilities. I usually quickly go through the mod's discussion page as well, as the most obvious mistakes, incompatibilities, and unannounced changes a mod introduces are usually repeated. Knowing what you're getting yourself into is even more important when it comes to weather mods, as they rely heavily on lighting (of exterior and interior alike!).

ELFX changes Skyrim's lighting "by adding lights to all light sources and removing any light without a source, as well as the addition [of] many more effects like smoke, volum[etr]ic lights, drip[p]les, etc." The author of ELFX basically went through every location in Skyrim and tweaked the presence, position, effects, and/or brightness of every light source, the settings of the weather system and every environment to accommodate those changes, and added additional effects if they so desired. This means it is really targeting vanilla Skyrim, and additional locales will very likely feel out of place, or be entirely too dark or bright.
There is however a long list of ELFX compatibility mods (see the Requirements dropdown menu at the top of the description).

Realistic Lighting Overhaul is less intrusive, and focuses more on improving vanilla lighting. Unlike ELFX, "changes made to this mod only utilize the game engine and changes are only made via the Creation Kit", "this mod does not aim to make the game fantasy like, or add lights for the purpose of it looking beautiful on screenshots", and "this mod adds a vast amount of ambient lighting, more shadow casting lights and bounced lighting. The lighting in RLO is very subtle and very balanced". It will lend itself better for a more seamless transition into new areas.

An even less intrusive lighting mod is Skyrim is Luminous (which is only available for the Special Edition). It "preserves the existing vanilla bulbs unlike ELFX or Relighting Skyrim which delete them". More importantly, "Skyrim is Luminous edits existing vanilla light records and templates, so it will be compatible with most mod added locations unless the author intended for their locations to have unique lighting".
In the latter case there is very little you can do anyway, apart from using the mods the author recommends, which might ruin the lighting of other locations. The best way to deal with that is to, again, thoroughly read the description and try to find out how the mod author dealt with lighting in the added environments.

The same mod author of Skyrim is Luminous, DrJacopo, also created the Luminosity Lighting Overhaul (also only available for SSE), which makes even fewer changes (Skyrim is Luminous incorporates this mod).
I mention it not only because its compatibility (in the sense of consistency with other mods' lighting) will be even higher, but also because it falls under the Cathedral Concept umbrella, which I happen to really like and certainly recommend.

That all being said, lighting overhauls do dramatically improve the appearance of Skyrim, and I find them quite indispensable. Vanilla Skyrim has a lot of frankly ridiculous light placements and properties, some of which cast shadows at strange angles, whereas others don't cast shadows at all (which is something you will notice once you start paying attention to it). Moreover, I have come across scenes lit by ELFX or RLO that had much more atmosphere than the vanilla lighting could ever conjure, making the game even more enjoyable.

In short: using lighting overhauls is a great idea, if you're willing to go through all the documentation of every mod you intend to use.