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I just took a picture of myself in one of those magnifying shaving mirrors and in the photo I am unmagnified! Why is this?

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Magnification depends on the object distance. Angular magnification is even more complicated -- it depends as well on the distance of the observer (camera) from the image. –  Ben Crowell May 19 '13 at 3:55

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I think the answer to this mostly has to do with psychology and not physics. When we estimate the size of something we use surrounding objects as a reference.

Here is a photo of me in a non-magnifying mirror:

photo with no magnification

After that I turned the mirror around to the magnifying side and tried to take an identical photo at an identical distance:

photo with magnification

Notice my hand over the mirror and the objects not in the shaving mirror look essentially the same size but the image in the mirror is magnified? Without the surrounding objects you'd have no way to estimate if the image is magnified or not.


For example, how tall is the Eiffel Tower?

Eiffel tower

Now what if we add a reference object into the image?

Eiffel tower with man

Notice how when you look at the second, it's easy to imagine the Eiffel tower actually being a small toy model?

I suspect if you re-take the picture with objects of known size in and out of the image you're brain will be able to use those objects as a reference and the magnification will show up as expected.

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