Ratios

With the advent of HDTV, all the reviewers talk about the new 16:9 screen ratio as opposed to the old - square - 4:3 ratio.

I always thought widescreen TV and widescreen computers were the same thing. Until I was trying to design a PowerPoint(r) presentation to show on a TV. I set the page size to 16x9 and it didn't fill my computer quite right. Then I looked at the actual resolutions.

HDTV is nominally 1920 x 1080 (pixels). My computer monitor is 1440 x 900. I could quickly divide and see that HDTV is 1.78:1 while the computer is 1.6:1. But how do these ratios compare - in integers?

I'll save you the suspense. HDTV is, in fact, 16:9. The computer turned out to be 16:10 - a little squarer so that a presentation to fill the TV will leave a little top and bottom on the computer.

Google Docs and Excel(r) have an advanced* function called =GCD - "Greatest Common Denominator". We all learned about the Least Common Denominator in the 4th grade, but what is GCD? It's the largest integer that will evenly divide both sides of a fraction. If you divide both sides of a fraction by the GCD, you get what I was looking for: a simple integer ratio.

You can download the worksheet+ as a picture or live Google Doc that you can use as your own. Either way, column J contains the formula (without the ' ) to fill in under the raw data.

* GCD may not work in Excel until you load the Add-In. From the Tools menu, select Add-Ins... and check Analysis ToolPak. When you click OK, it may ask for your original Office CD to load the component.