External monitor for MacBook 4,1

Question

Hello all,
I am wanting to run an external monitor for my old 2008 MacBook 4,1 13"
I understand that I can run a 1920 x 1080 monitor via my machine.
However, I don't know the upper size of monitor that goes to.
I have plugged it into a 40" screen, and the image was not sharp.
I plugged it into a 23" screen, and the image was sharp.
I am wanting to know the largest screen I can run, and still have a sharp image
Thank you for all time, and Merry Christmas everyone.
Sincerely, Xiao Ping Guo

Answer 1

The inch dimensions of the screen don't matter. The pixel dimensions, 1920 x 1080, can be sharp enough depending on the viewing distance. What matters is if the number of pixels and screen size are properly coordinated with the viewing distance.
On a 23" diagonal screen, 1920 x 1080 is about 96 ppi. On a 40" screen, 1920 x 1080 is about 48 ppi, or about half the resolution. The 40 inch screen should look half as sharp as the 23 inch screen, because the same number of pixels (1920 x 1080) is being spread over twice the area.
If the 23 inch is a desktop monitor, it is meant to be viewed at about desk distance, or about 2 feet. If the 40 inch is a TV, it is meant to be viewed at sofa distance, or about 10-12 feet. If you are viewing a 40-inch TV only a couple feet away, it will seem unsharp because it is not intended to be seen so close. At a normal TV viewing distance, 1920 x 1080 at 10 feet should look sharp enough.
If you want the 40 inch to be as sharp as the 23 inch than the 40 inch must display more pixels. That's why 4K screens are becoming popular. But the MacBook is at its limit already.
The reason I originally said the inch dimensions don't matter is that a screen of any screen will look sharp at its intended distance. Your MacBook could drive a 100-foot screen at a stadium at 1920 x 1080 pixels and it would look sharp enough, from the seats. If you're 2 feet from that stadium screen every dot will look coarse and huge, but that's not how close you're supposed to view it.