In photos it's always a supermoon
November 14, 2016 5:57 AM   Subscribe

Why does the moon appear so much bigger, relative to other elements in a photo, than it does in real life?
posted by LonnieK to Science & Nature (9 answers total) 3 users marked this as a favorite
I'm assuming this pic isn't photoshopped. But even if it is, plenty aren't.
posted by LonnieK at 5:59 AM on November 14, 2016

That looks photoshopped to me.

That said, the moon does not look bigger in photos, it simply looks very large sometimes when it's near the horizon. See here for an explanation.
posted by selfnoise at 6:06 AM on November 14, 2016 [2 favorites]

This is achieved by taking the photo from a far-off vantage point relative to the terrestrial portion of the photo, with a very long (telephoto) lens. This results in what is called lens compression.

For a moon-based example, check out this write up on such a photo.
posted by tocts at 6:07 AM on November 14, 2016 [25 favorites]

Here's another article about how a photographer got an amazing moon image. She was over 1.5 miles away from the human subject of the photo.
posted by Orlop at 6:09 AM on November 14, 2016 [7 favorites]

Huh, okay, focal length compression had not occured to me. Which is pretty dumb because I was just explaining to my daughter this weekend why the moon "follows you home".
posted by selfnoise at 6:10 AM on November 14, 2016

For the record, most of these shots are composites; one photo is taken of the foreground, then a close-up shot of the moon, mix in Photoshop. It would be difficult if not impossible (maybe doable with graduated filters) to expose for the extremely bright moon and get that visible city in the same shot.
posted by Nyx at 8:20 AM on November 14, 2016 [2 favorites]

it is not lens compression. in the article linked by tocts, it says quite clearly that "It is because we tend to stand farther away from our subjects when we use a long lens" and you cannot stand (significantly) nearer or closer to the moon.

it is a combination of two things: the poorly understood effect of the moon on the horizon looking larger that's covered by selfnoise's answer and the fact that photos taken with a telephoto lens have a narrow field of view, much smaller than you assume when looking at the photo.

a simple way to understand the latter point is that it's not "wow the moon is as wide as that huge castle", but "oh, the moon is only as wide as that distant castle which is so far away it's a tiny dot on the skyline".
posted by andrewcooke at 9:09 AM on November 14, 2016 [5 favorites]

Think of it in terms of cropping. Start with a picture in which the moon appears small. If you crop it, the moon appears bigger. If you crop it close, the moon appears huge. Use of a telephoto lens has the same effect as cropping, except a sharper picture can be obtained.

Normal vision is very wide-angle compared to a camera lens. If you ever tried take a picture of a mountain range, for example, you will have found it very hard to get a picture that reproduces what you see yourself. So even a "normal" picture can seem cropped by comparison with normal vision.
posted by SemiSalt at 4:19 PM on November 14, 2016

1. The linked example is photoshopped, according to the photographer. There are a lot of photoshopped moon pictures.

2. It is definitely the same effect as lens compression, but there's no need to involve lenses to think about it. Angular size is the key—the moon is always about half a degree wide, because you can't get appreciably closer or further from it. But your subject sitting next can be any angular size you want. If I take a picture of a 6 foot tall person from about 600 feet away, they are going to be about 0.5 degrees high, and they'll look as big as the moon. Use whatever lens you want to photograph that scene; the lens doesn't matter. (One could argue that "lens compression" is a misleading term for "stepping back from your subject".)

3. Cropping and field of view are irrelevant because we are talking relative size (per the original question text). I can't make a person fill the same angular size as the moon in a picture by cropping.
posted by kiltedtaco at 7:48 PM on November 14, 2016 [1 favorite]

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