how to know if the screen brightness is reduced on battery mode?

hey, i'm checking dell latitude e5570. after asking Dell, i still don't know the answer.

Is there a way to know if the screen brightness is reduced when the laptop isn't plugged to ac power?
Is "Regulatory and Environmental Compliance" got anything to do with it?

Regulatory and Environmental Compliance:
ENERGY STAR
6.1 EPEAT Gold Registered

thanks

 

Screen brightness depends on your OS's behaviour. Dell doesn't control it.

The compliance has nothing to do with this.

 

thanks, so how to tell?
in some laptops (toshiba especially) it's not possible to bypass the brightness level (change power saving mode, disable the sensor etc).

 

Personally I've had no issue with messing with brightness settings on any OEM's laptop, Toshiba included. As Koala said, it's a control managed by the OS.

 

Every Dell Laptop with the exception of the previous XPS 13 don't have an auto brightness sensor or you can disable it (Dell got a lot of flak for the lack of an option to disable the one on the old XPS 13). If it has a sensor, disable adaptive brightness in the OS and set every power plan to whatever brightness level you want. If you set them all to 100%, you won't see a change going from Ac to battery. By default in Windows, on battery is usually at lower brightness settings to save power, but that is super easy to change manually. Dell doesn't pull any third party power management utility shenanigans unlike some other manufacturers anyways.

 

thanks, i still don't get it..
here is some data from notebookcheck review for dell latitude e5550 :

brightness:
Maximum: 343 cd/m² Average: 319.9 cd/m²
Center on Battery: 219 cd/m²

why would notebookcheck emphasis the "center on battry" data if it's an OS issue?

 

It's not an "issue", it's a setting. They are giving this as a way to get an idea of how bright it is on the default install settings on battery. That data is meaningless without any kind of context, they don't say at which brightness setting that was taken and without that you can't make a comparison to other brightness settings.

For example, take any laptop and crank the brightness to max on both AC and battery, I can assure you, you won't see a difference.

 

Samsung used a light sensor plus adaptive brightness on some of their notebooks which sometimes required some effort to get under control. However, I've had no such issues on Dell notebooks.

Just be aware that under light usage, the screen backlight, at high brightness, can use more power than the rest of the system combined. Here's a graph I made a few years ago for the Samsung NP900X4C which shows the imcremental change in power consumption as I increased the brightness from minimum to maximum.



On that machine the system power drain increased from 6W to 10.5W. More modern notebooks with better power management have lower idle power drain (I've seen my Dell E7450 run on around 4.5W). Any user who wants decent run time on battery either has to carry a big battery or compromise on display brightness. However, some manufacturers (the Lenovo T420s I once owned comes to mind) can get good battery life statistics by limiting the display brightness.

John

 

So whats happening with toshiba laptops? There are many reviews on notebookcheck for toshiba models, and it seems like theres a common problem with the reduced brightness in battery mode. I saw a lot of reviews but toshiba excels.
I'm also pretty sure that i saw on the toshiba website more information about reduced brightness in battery mode.


This is taken from toshiba website:
Product disclaimers and legal information:
Maximum brightness is only available when operating in AC power mode. Screen will dim when the computer is operated on battery power and you will not be able to increase the brightness of the screen.

 

Without reading said reviews or having time with an actual unit hard to say. As John said, some notebooks use an ambient light sensor which is turned on by default, however, it is usually possible to disable these entirely.