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SYFY WIRE Bad Astronomy

UPDATE: Fake TV Ads, Pixels, and Parallax

By Phil Plait

Yesterday, I ran a post I figured would generate some buzz, and it did. But it turns out I was wrong about why it would do so! To make it more fun, I wasnât exactly wrong in the article, but I wasnât exactly right, either. Thereâs enough to warrant a brief update, because honestly, this stuff is cool.

In the article I dissected a commercial for an ultra-hi-def 4K TV set, where people walk into what they think is a job interview, but is actually an elaborate prank. During the interview what they think is a window on the wall is actually a TV showing a cityscape. During the interview, an asteroid is seen coming in, slamming into the city, and wreaking havoc.

The ad is to show that the TV display is so good, so real, it can fool people into thinking itâs the end of the world (or their local piece of it). I wondered, though, if that claim is legit, and if in reality people would notice the TV wasnât real due to seeing the pixels in the screen (which in turn would mean the ad was faked, using actors). So I did a little math and concluded that given the sizes of the pixels in the TV, the resolution is indeed high enough that pixelation wouldnât be a problem. Therefore, I labeled the ad as âplausibleâ.

Thatâs where I figured people would quibble; the resolution of the human eye is a fascinating and eminently arguable topic. But in fact, thatâs not what happened. I immediately did get a lot of responses in the comments, via email, and through Twitter, but they were not about my math. They were about parallax.

Parallax is the effect where you see a different perspective on an object as you change your viewing angle. For example, hold your extended thumb in front of your face. Now close one eye, note your thumbâs position, and then open that eye and close the other. Your thumb will appear to move as your viewing angle changes.

This effect is what gives us depth perception, and tells you why nearby objects like trees fly by when you drive past them, but distant mountains move more slowly.

After reading some of the comments on my article, I agree that parallax is an issue in the ad; if you paid attention walking into the room youâd notice the view on the TV screen seems flat, with no depth. As I note in the article, though, I donât think a lot of people would be paying attention to the window; theyâd be nervous about the interview, and would be paying more attention to the interviewer. So that by itself might not be enough to claim the ad was faked with actors.

However, thereâs more. I chatted with Randall Munroe (of xkcd) about this, and he noted that the viewing angle of the prank victims changes when they sit down versus when theyâre standing up. The âwindowâ shows the tall buildings and much of the ground in front, and itâs unlikely theyâd see the ground once seated if the window were real. That would definitely look very odd. Also, he noted that as the victims walk into the room the view out the window would change as their distance to the window changed; theyâd see more to the sides as they approached. Try this yourself; walk toward a window and youâll see the overall view left/right changes. This is pretty obvious, and should at least register subconsciously.

This video should help you picture this. Itâs actually extremely cool:

Iâll note that I agree with these arguments. Parallax may be the key issue here, and anyone paying even a small amount of attention should notice it. But still, I wonder⦠my friend (and evil twin) Richard Wiseman is a psychologist who has literally based his career on people not noticing things. This is called change blindness, and he has masterfully made videos demonstrating it. My favorite is âThe Color Changing Card Trickâ.

Did you catch all the tricks? Iâve seen many videos by Richard where people miss things so incredibly obvious youâd swear the video was faked⦠but it isnât. People really can totally miss obvious things if theyâre distracted.

Now, this isnât to say the video is real, that is, not faked with actors. It very well may be. In fact, after reading the comments I think Iâm leaning toward it being faked. Iâd bet that way, but I canât prove it using these parallax arguments because I know how important these psychological effects are. Itâs possible they filmed 50 people, 47 of whom werenât fooled, and three of whom were.

Iâll note that other commenters pointed out various other factors as well. For example, some folks claimed a TV doesnât have the contrast to realistically fake an actual window, but I wouldnât agree with that necessarily. The room could be darkened a bit to brighten the TV, and modern TVs have astonishing contrast between light and dark. That kind of thing can be controlled by an accomplished prankster, as can other factors. Again, I think this falls into the âmaybe, but Iâm not convinced by this particular argumentâ category.

Also, a mea culpa, kinda: After reading some of the parallax arguments (but before chatting with Randall) I updated the article acknowledging I shouldâve discussed them more, but felt they werenât critical. Clearly I shouldnât have dismissed them so casually, but I still donât think they clinch fakery. What we really need is to do this same prank under more controlled circumstances and see how people react. I think that would be fascinating (though maybe a less intense view out the window might be useful; some folks can be shown just a static scene, while others might see an airplane or flock of birds moving across, or something else in the foreground).

In the end, I think my resolution argument stands, and the pixels wonât give away the trickâand that was in fact the narrow point of my post, and I shouldâve made that more clear in the end. However, parallax is certainly a different issue, and clearly provides a different angle on the argument.

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