[Xiaomi Mi 8 SE Themes, Apps, and Mods] guglicap:
Hopefully.

Tested on: RR ROM (not GSI) from https://build.lolios.ml/sirius/

GCam version: Arnova's Advanced 1.5 Download

Config xml file: see attachments Alternative Download

Disclaimer

If you're not using my same setup I can't guarantee the same results, though I think this should apply, for the most part, no matter the ROM you're using. If you're using a GSI I think it should work the same as long as you have flashed the gcam fix zip (or Magisk module).

Introduction

I chose Arnova's mod because it's the most customizable out there. To get it working straight out of the box:

Install GCam

Create directory /sdcard/GCam/Configs if it doesn't exist

Move xml config file to the directory

Long press on the GCam icon and select "Take a video"

Double-tap on empty space below shutter

Choose the xml file from the menu and click restore

Step 4 is necessary because trying to lauch with the defaults options results in a crash, but not in video mode. We're using this as workaround to import the settings in order to fix the crash and configure the camera.

I'll now describe every setting that I chose to edit so that you can understand why I set it up the way it is. Most of these settings are based on personal preference so feel free to experiment for yourself.

Settings

Mod settings - Advanced - FIX - RAW10 in front

Enabled.

Fixes the camera crash on app launch.

Mod settings - Advanced - FIX - Buffer Fix

Enabled.

Fixes viewfinder lag. Doesn't fix it for Night Sight. Also, I remember this wasn't needed when using GSI + gcam fix zip so if you're using a GSI maybe try disabling this and see how it goes.

Autoexposure correction

1/10 sec.

This setting is very important. It controls the balance between noise and blurriness / time it takes to shoot a frame.

Basically, here's what this does. When you take a picture there are a few factors that influence how bright the picture will be. These factors are width of the objective, time the camera spends taking the picture (also known as shutter speed) and the sensor sensitivity (also known as ISO). Unlike regular cameras, the width of the objective is fixed (I believe) so on our phone we're limited to ISO and shutter speed. The longer the shutter speed, the more time the sensor is exposed to light, the brighter the picture. If you're not steady though, longer shutter speeds will result in blurry photos. Increasing ISO, on the other hand, will allow you to keep shutter speed low and have sharp images, but will significantly increase the amount of noise in the picture.

What this setting does is set a limit to how high the shutter speed can get before it will resort to increasing ISO if it needs to. The default settings of Off gave pretty bad results for me - picking 1/50 and 2000+ ISO where 1/10 and 300 ISO did perfectly fine - though feel free to experiment for yourself. Keep in mind the actual time to take the pic will be at most this setting times the HDR+ parameters setting. So if you have the default setting of 9 for HDR+ and 1/10 like I do it will take at most 0.9s to take a picture.

Correction NightSight

1 sec.

Same as Autoexposure Correction but for Night Sight mode. I set this to a very long time but it's totally personal preference so feel free to tweak this. As you may have guessed, I really dislike noisy pictures...

Pixel 3 AWB

Enabled.

See the GCam ports site relative FAQ.

I found it produces warmer colors. It also seems to only work if you use Pixel 3 or Pixel 3XL as models. Feel free to change.

Mod settings - Advanced - Base - Model

Pixel 3 for both cameras.

Tested other models and didn't find any difference except Pixel 3 AWB stopped working except for Pixel 3XL.

Mod settings - Advanced - Noise reduction

Everything disabled.

Trying enabling them but they didn't really seem to work so I left them off.

Mod settings - Advanced - FIX - Using Sabre

Auto.

Sabre FAQ. I left Auto because I have no clue what that's supposed to mean. Tried both On and Off and they worked but I couldn't spot a difference. It supposedly makes pictures better though, so set to On if you'd like.

Mod settings - Advanced - Libs

Stock by Google.

I just left the default because I tried the other ones and found no difference. Try them for yourself if you feel like it.

Mod settings - Advanced - Enable Auto exposure

Disabled.

This is weird one, most of the times it crashed the app right after shooting (didn't store the pics), other times it worked but I saw no difference. Don't think we're missing out on anything.

Photo - Advanced - "Motion" function

Disabled.

Enabling crashes the app, it might work with different models settings / configs (in Mod settings - Advanced - Base) but I didn't bother because I don't really care for it. If you somehow get it to work, please report back. Thanks!

Photo - Advanced - Optical Stabilization (OIS)

Disabled.

MI 8 SE doesn't have OIS. Not much to say.

Video - Advanced - Init SlowMo with

120 FPS.

Setting this to 120 FPS instead of the default 240 FPS allows to use both 1/4 and 1/8 speed for slow motion.

By the way, I believe that while most of this guide should also apply to GSIs, iirc slow-mo is broken on GSI and there's not much you can do about it. Sorry.

I hope to have cleared up the confusion about GCam, I surely was very confused when I first started looking into it and was quite overblown with all the settings.

Let me know if you know about anything that could be added to the guide.

Thank you!