# How do the internal elements of a 28-80 mm lens differ from a 28-200 mm lens?

I'm trying to follow an I'ble posted by Patholio (fisheye lens, https://www.instructables.com/id/cheap-fisheye-lens/).
He used an element of a 28-200 mm lens. I have disassembled a 28-80 lens, but the results are less spectacular even though the focal length at the low range (28mm) is the same. I can imagine that the elements of both lenses differ, hence the difference. Is this the explanation?

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7 years ago
Yes, the radius of curvature of the lenses is the key to the depth of your fish-eye effect.

Steve
bertus52x11 (author)  steveastrouk7 years ago
So the radius of the element that causes the fish-eye effect in a 28-80 lens would be larger than the radius in a 28-200 lens?
7 years ago
yup
7 years ago
You could have just said "About 120 mm".  ;-)
I'm not sure I understand your comment.
7 years ago
Joke. 200mm - 80mm = 120 mm difference.
ok, I get it!  :-)
7 years ago
I never said it was a funny joke....
Reminds me of a joke of an old teacher who said: water boils at 100 degrees (C) and not 90, because thats a straight angle.
BobS7 years ago
I disassembled a 100-300 mm zoom lens, and no fish-eye component came out...
bertus52x11 (author)  BobS7 years ago
But that makes sense...