Optical illusion in the mountains ― can someone explain?

[Brian K]

Here’s an example to help compare – Mount Adams in the Cascade Range.

I’m 10 miles away, at 3,000 feet, and Mount Adams is a 12,000 foot mountain. So in this example, I’m considerably closer to the mountain, I’m about 1,000 feet lower than before, but this mountain is much, much higher than Mount Olympus. The midrange mountain is several hundred feet higher than my tripod location.

Another leveled camera, but it’s my 240mm lens this time.

Tachi 4x5
Fuji A 240mm/9
(w/ Lee orange filter)
Ilford FP4+ (in D-76)
Epson 4990/Epson Scan

Here's a simple thing to remember, when things are far away from you they look smaller, even really big things.

[Steve M Hostetter]

You see mountains behind taller mountains which in my mind is do to refraction or the bending of light rays..

[Kevin Crisp]

Things that are further away look smaller. All parts of things further away look smaller. Not as wide, not as tall. This leaves you unable to judge their relative height by size alone as you move further away, though snow line and tree lines can give visual clues.

If it didn't work this way -- things look smaller as you move away but not on their vertical axis -- you'd be seeing a soaring, extremely skinny mountain, A great distances they would look like skinny but extremely tall pillars.

The curvature of the earth would take a little, maybe 30 feet from a distance of 20 miles, but not enough to be a factor.

[Struan Gray]

Things that are further away look smaller.

There is a further factor, which is that our binocular vision becomes pretty inaccurate beyond a hundred meters or so, and fairly useless after a kilometer/mile. This makes the assessment of size fraught with error. K2 is famously K2 and not K1 because a closer mountain (Masherbrum) appeared taller to the original survey team.

We actually use the fact that things look smaller as they get further away - and clues from leading lines in the landscape - to compensate, but that means you can easily be fooled by terrain. Marksmen, for example, learn to mentally adjust their impressions of distance if the ground between them and the target is not flat - a valley makes distant objects look closer.

Once you get beyond the middle distance, your brain starts telling you fairy stories. A classic is the way that a sunburst through clouds (or crepuscular rays) appear to diverge away from the sun. In fact, the light beams are very nearly parallel, it's just that we do not perceive their varying distance - our brains prefer to see a set of diverging rays. Mountain shadows are almost always triangular, whatever the shape of the mountain, for the same reason.

[Bill_1856]

I can't speculate about the illusion, but that first picture is very nice. Thanks for posting it.

[Paul Metcalf]

Once you get beyond the middle distance, your brain starts telling you fairy stories. A classic is the way that a sunburst through clouds (or crepuscular rays) appear to diverge away from the sun.

X2. Another one is that the size of the (full) moon appears bigger when it's near the horizon compared to when it's further up in the sky.

I think there is also some optical illusion going on with the use of a 110 (WA) compared to the 240 in your second photo.

[Nathan Potter]

I think to a first order the illusion is perspective distortion as implied by some above. A switch to longer tele lenses for the particular format will reduce the effect of the illusion. But if I look at your first image I agree with Frank, the distant peaks don't seem lower because I tend to automatically correct my vision for such a perspective effect just due to experience.

Nate Potter, Austin TX.

[Vaughn]

It is not an optical illusion, it just looks like one...

[tgtaylor]

"Relative size - If two objects are known to be the same size (e.g., two trees) but their absolute size is unknown, relative size cues can provide information about the relative depth of the two objects. If one subtends a larger visual angle on the retina than the other, the object which subtends the larger visual angle appears closer."

-Wikipedia.

[Scott Knowles]

If you extend the line of sight from you (camera base) to the distant mountains it's likely you'll see it's below the peaks (accounting for any slight curvature of the earth) and the angle between the base and the peak would determine the elevation difference. It's similar to plane-table surveying and mapping used in the 1900's, see photo from USGS.