Screen upgrade LTN156HL01-102 for Dell E5550

Hi everyone,

After several hours of googling over a couple of days, I couldn't really find proper answers to my questions, so I figured the only thing left to do is to ask the good people of internet.

Here's my story.

I bought a Dell E5550 back in 2016, I was glad with it, it was performing well for me (web browsing, some MS Office, some coding, and of course Netflix), it could even run FIFA 16 decently but I haven't tried any other games. In fact, I am still happy with it that I don't see the need to get another laptop in the near future, instead, I fixed what needed to be fixed: I replaced the battery a few months ago (with an OEM one) because the first one died, and I just recently upgraded the screen because it was really the only thing bothering me with this laptop, 1366x768px is pretty low for a 15.6" screen.

This brings us to the matter at hand, I bought a Samsung LTN156HL01-102 panel and I installed it on the laptop, it's working fine, however, I feel like the brightness isn't where it should be, this panel is supposed to be 300nits but I feel like it is not much brighter than the 220nits TN panel that was originally installed (I checked the actual specs after I removed it). On the other hand, I have another Dell laptop, for work, that is equipped with BOE NV156FHM-N43 (checked with HWinfo), this panel is supposed to be 300nits also but it is so much brighter than the Samsung. I actually compared them both in the same almost-no-light conditions using the light sensor of my phone, I know it is not an accurate measuring device, but it gave me an idea about the brightness difference, turns out the NV156FHM-N43 is 50% brighter than the LTN156HL01-102. Now, if I didn't have this other screen to compare with, I would probably never care about this, but now I have questions, and I hope someone can help with some explanation.

I read that contrast measurement is not standardized between manufacturers, but could that also be the case for brightness measurement with nits? It shouldn't be the case, really.

NV156FHM-N43 has an 800:1 contrast ratio, while LTN156HL01-102 has 600:1. Could this justify the first being brighter?

Does brightness decrease over time for IPS panels? HWinfo says that my LTN156HL01-102 was manufactured on Week 0 of 2013, while the sticker on the back of the panel said November 2019. I don't know which value to trust, but if the panel is actually 7 years old, could it explain why it wouldn't be as bright as it should be?

I read that some laptop makers, including Dell, pre-configure a list of compatible screens in the BIOS, so when replaced with a panel that is not in that list, some things don't work as expected like the brightness. I have to say that for me, everything seems to work fine, even the brightness controls on Windows 10. To make sure I wasn't missing anything, I updated the BIOS from Dell support website to the latest version, and I re-installed the default Monitor driver on Windows 10 but nothing changed. Is there a way to change the brightness scale in the BIOS?

Both panels are obviously 30pins but the original TN panel has 1 lane while the Samsung has 2 lanes. More lanes = more power = more brightness? I would suspect the cable but since FHD resolution requires 2 lanes and the screen actually works, I don't think the cable needs to be changed.

I read some stuff about LCD inverter, is that relevant to IPS panels also?

Sorry for this long post, but I really want to understand what's the deal here. I'm probably not going to do anything about if it's too complicated to fix but at least, I would like to know the how and why of this.

Thanks guys and stay safe!

PS: There is no datasheet for LTN156HL01-102 but it should be the slightly improved version of LTN156HL01-101 for which there are available datasheets.