# Demonstration of focal length distortion



## ksmattfish (Jan 18, 2005)

These are scanned from slides I use to show my photo classes what some of the effects of choosing different focal lengths are.  They were taken on Fuji Sensia 200 slide film with a Pentax ZX-5 35mm SLR with a 28-200mm zoom lens.  

In each photo I have attempted to keep the height of the fountain bowl the same, and the fountain itself in roughly the same place in the composition.  I set the zoom lens to a particular focal length, and then adjusted my distance to subject to keep the distance between the bottom and top edge of the basin the same.  

It's easy to see how the gazeebo in the background and the octogon shape at the base of the fountain are affected with the different focal lengths.  More subtle, but still there, are changes in the appearance of the fountain itself.  Since this was taken with a 35mm camera the 50mm focal length is considered "normal".  For more info on focal lengths check out this thread

http://www.thephotoforum.com/forum/showthread.php?p=153611#post153611

28mm (wide)






35mm (wide)





50mm (normal)





70mm (telephoto)





100mm (telephoto)





135mm (telephoto)





200mm (telephoto)


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## vonnagy (Jan 19, 2005)

ta matt this is a very good demonstration. I often switch between my 15-30mm wide and 85mm prime. Comparing the two really makes the the wide angle stuff look quite distorted (even with digital zoom)


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## oriecat (Jan 19, 2005)

Those are great examples, Matt!  I also like how easily you can see the differences  between how far apart the gazebo and the fountain appear.


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## Big Mike (Jan 19, 2005)

Fantastic demonstration Matt.  Thanks.


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## Unimaxium (Jan 20, 2005)

Wow. It's amazing how much closer the background (esp. the gazebo) looks as you increase focal length. I had known that closer focal lengths create more distortion and that longer focal lengths flatten the depth of field (or lengthen, depending on what you're describing in terms of DOF or whatever), but I never knew that it enlarges the background like that. Very useful.


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## cw_ (Jan 24, 2005)

great demonstration! thanks for that.


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## ksmattfish (Jan 24, 2005)

These were taken using the same film and equipment.  This time I didn't move the camera.  Changing focal length without adjusting camera to subject distance only changes magnification of the image.  Everything else stays the same in it's relationship (size, perspective...) to other parts of the image.  

28mm





35mm





50mm





70mm





100mm





135mm





200mm


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