I want to share with you this week's adventure with my new (external) 20-inch monitor with a maximum resolution of 1600:900. When try to install it, I learned that 1600:900 does not appear in the slider options in Control Panel-->Display-->Settings.
Why not? During a week of trouble-shooting, I learned that this new monitor has an aspect ratio of 16:9 and is not compatible with my SL400's screen with an aspect ratio of 16:10. The maximum resolution I can use for both the laptop and external monitor is 1280:800--and cannot use the stated maximum resolution of 1600:900.
Display Properties usually offer a number of resolutions based on your monitor and video card. To pick one that does not distort, the first number divided by 16 should equal the second number divided by 10. I have not used one of these, but I’m pretty sure you can choose a Portrait setup physically and in Display Properties. (Of course, then you’d want to switch the 16 and 10 above.)
I believe that the current 20-inch monitors are 16:9, so this problem should be widespread. So it wouldn't matter which 20-inch monitor I would have bought.
In Lenovo's online forum, a lot of people were discussing this problem and the consensus was that is was caused by a driver or BIOS problem. So I installed a new monitor driver and the newest BIOS. But the problem persisted. And finally someone at Lenovo figured out the aspect ratio issue.
So if I want to use a 20-inch monitor, I will need to be satisfied with the 1280:800 resolution--not the 1600:900 as advertised on the monitors on the market. According to the formula, the 1440:900 should work but it cuts off the bottom task bar.