New McDonald's Menu Item - A Blog Post!

As I said in my last RAGBRAI post, after the bikers take off in the morning, I like to linger over breakfast and read the paper.  In Omaha, where the bike ride originated this year, after doing my cooler and snack shopping, I stopped at the McDonald's at 40th and Dodge.  Breakfast was uneventful, but as I was gazing out the window, I saw a blog post!

Even regular readers of this blog likely don't realize it, but at the bottom of the page, there is a link to "FEEDJIT", which tells us who is reading the blog and what they are looking at.  Of course, there are limitations, it identifies not actual readers, but lists the city where their ISP is located, and how they got to the blog.  Interestingly, one of the most popular posts I've ever written is the one on Moiré patterns!  For some reason, the patterns created, usually from a pair of overlapping screens, stands out and yells to me!  In this case, from inside McDonald's, it was caused by the overlapped screen patterns of window advertising!  The view from the outside is innocent enough - shown at left.

But the view from the inside, to someone who (at least sometimes) notices the little things, was very different!  Shown at left is above's left window from the inside.  The Moiré pattern I noticed is in the overlap areas - note that the overlap pattern at right is different from the overlap at left.  Click the image to see a larger version.  What causes it?  Well, the advertisement is not a solid graphic - it has little holes in it...  I know that Tucson has requirements for convenience stores to unblock windows so that the inside can be seen from the outside at night - a theft deterrent.  By putting the little holes in the graphics, they become at least partially transparent to see inside at night, and like these pictures show, you can see outside during the day.

The key for the present experiment is that when the holes are put into the graphic, or if they exist in the substrate before processing, they come out with different hole spacing!  As a result, when they are overlaid on each other a Moiré pattern results.  In fact, when you click and load the left image you may get a checkerboard pattern on your screen as the hole pattern interferes with the pixels on your viewing monitor. The picture at right and near left show the overlapped areas with more resolution so that you can spot both the hole pattern in the graphic and the resultant Moiré pattern.  While the pattern on each of the graphics looks identical, if you look at the full-size version and put a ruler up to the screen you can see that the patterns have slightly different spacings.  Because the Moiré patterns are different, we know that all three of these graphic screens are slightly different in size or frequency.  Even though the 2 outside graphics don't overlap, we can tell that if they did it would result in a different Moiré pattern!

Going back to the very top picture of the
advertisement from the outside, the right hand part of the graphic has a totally different look from the inside.  The main reason is that the graphics have no, or almost no overlap.  However, there is a window sun screen that is used to block part of the incoming light.  The screen, as shown at left, has a regular pattern that hangs down over the graphics.  The resultant set of Moire patterns between graphics and sunscreen is shown at right.  It is quite intricate and again, is different over different graphics showing that the hole spacing differs slightly.  At least to me it is very eye catching, though most people would likely not see the patterns, let alone realize what causes it or knows its name!  I would file it under "frequently seen but rarely observed" - my moniker for details from everyday life that few ever notice.

And while not listed on the menu at McDonald's, I got a big kick out of it.  And after seeing this my first day of the ride, I went looking at other outlets for similar effects, but never saw it again.  Keep your eyes out!