Portal makes scene darker

[gantork]

Hello, I'm having a very weird problem with a scene, where adding portals make the scene drastically darker and changes the lighting overall. I can't see any errors in my process, just portal material applied on planes, and I tried placing them perfectly fitting the openings and also slighty outside.

There's two images attached, the darker one has portals activated.

Thanks in advance.

[maru]

What kind of environment lighting are you using?
Can you share this scene with us? (uploader is in my signature)

[gantork]

I'm just using an HDRI, but after testing I've noticed that it only happens with sunny HDRI's when I have a number greater than 1 on the output amount. I tried it with some blue hour ones and with just a white color as an environment, and the problem doesn't seem to happen.

I will upload the scene now. Best regards.

[maru]

(converted into a support ticket #17986)