please do not take this the wrong way im just trying t help u all
Well, it's a little complicated, so hopefully I can explain it without making myself sound like a dingus.

First, navigate to \SOMA\script\player\

It's a good idea to make a backup of the "Player.hps" file before we change anything, just in case.

Open the "Player.hps" file in a text editor (notepad is fine)

Use ctrl+f and search for "float mfFlashlightRadius"

By default it should be at 10.0f

Increasing the radius will also make it appear brighter (changing it to 20.0f, for example, will double the range and significantly increase the brightness.)

(Don't forget the "f" at the end of the number!)

To modify the brightness alone, without changing the range:

Near the top of the file, there should be this line:

const cColor gFlashlightColor = cColor(1.4,1.6,1.7,0.7f);

There are four numbers here, the last of which is the brightness (0.7f) which could be changed to 1.4f to roughly double the brightness, or 5.6f to octuple it if that's what you're into.

Once the desired changes are made, make sure to save the file and it should work :)
iam not a thief nor a spamer just rying to help all of u Soma fans out there