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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 12 Nov 2011 (Saturday) 21:46
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What makes a fisheye a "fisheye"?

 
Snydremark
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Nov 12, 2011 21:46 |  #1

If both of these lenses have the same focal lengths, how is one a "fisheye" and one one not? I'm just kinda confused by this one...

Sigma 8-16mm (external link)

Canon 8-15mm (external link)

Thanks!


- Eric S.: My Birds/Wildlife (external link) (7D MkII/5D IV, Canon 10-22 f/3.5-4.5, Canon 24-105L f/4 IS, Canon 70-200L f/2.8 IS MkII, Canon 100-400L f/4.5-5.6 IS I/II)
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thestone11
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Nov 12, 2011 21:59 |  #2

Coz the sigma is designed for crop sensor as a ultra wide angle lens, not fisheye! On the other hand, the canon is a full frame format lens!


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sbattey
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Nov 12, 2011 22:15 |  #3
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My understanding is that fisheyes are just ultra wides that aren't corrected for barrel distortion.


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jra
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Nov 12, 2011 23:30 |  #4

A fisheye lens will not keep straight lines straight in a photo unless they are dead center through the frame. The closer to the edge of the frame a straight line gets, the more curved it will appear in the photo if taken with a fisheye lens (hence the "fisheye" effect). A rectiliniear lens will always keep straight lines straight no matter where they fall in the frame.
http://en.wikipedia.or​g/wiki/Rectilinear_len​s (external link)
http://en.wikipedia.or​g/wiki/Fisheye_lens (external link)




  
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Snydremark
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Nov 13, 2011 00:33 |  #5

Thanks guys; I'd thought it was just a side effect of having such a wild angle of view.


- Eric S.: My Birds/Wildlife (external link) (7D MkII/5D IV, Canon 10-22 f/3.5-4.5, Canon 24-105L f/4 IS, Canon 70-200L f/2.8 IS MkII, Canon 100-400L f/4.5-5.6 IS I/II)
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mike_d
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Nov 13, 2011 01:09 |  #6

The tradeoff is in field of view. Canon's 14mm rectilinear lens has a 114 degree FOV while the 15mm fisheye has a 180 degree FOV.




  
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Snydremark
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Nov 13, 2011 10:43 |  #7

wow...that's a significant difference there. But, everything not dead center of the 15mm shot would look all 'gumby-fied" vs the 14, where everything would still look, nominally, normal; right?


- Eric S.: My Birds/Wildlife (external link) (7D MkII/5D IV, Canon 10-22 f/3.5-4.5, Canon 24-105L f/4 IS, Canon 70-200L f/2.8 IS MkII, Canon 100-400L f/4.5-5.6 IS I/II)
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mike_d
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Nov 13, 2011 11:03 |  #8

Snydremark wrote in post #13393436 (external link)
wow...that's a significant difference there. But, everything not dead center of the 15mm shot would look all 'gumby-fied" vs the 14, where everything would still look, nominally, normal; right?

Any straight line not through the dead center of the frame will be curved with the fisheye. The effect gets progressively more pronounced as you move toward the edge of frame. Its not always as crazy looking or as obvious as you'd think. Composition and perspective makes a huge difference. Take a look in the image archive to see what I mean.

The 14mm would indeed keep straight lines straight even at the edge of frame. Perspective is still critical with any ultrawide angle lens. Rectilinear lenses tend to have a stretched appearance in the corners so you have to know how to deal with it.




  
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Snydremark
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Nov 13, 2011 11:56 |  #9

interesting; thanks, Mike!


- Eric S.: My Birds/Wildlife (external link) (7D MkII/5D IV, Canon 10-22 f/3.5-4.5, Canon 24-105L f/4 IS, Canon 70-200L f/2.8 IS MkII, Canon 100-400L f/4.5-5.6 IS I/II)
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TTuna ­ Eye
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Nov 13, 2011 16:01 |  #10

I don't know if you use Lightroom but it has lens profiles for most WA lenses that removes a lot of the distortion. I have a Tokina 10-17 that is very popular for underwater photography and was able to find a profile that someone made for it that I loaded into LR which really improved the images. I found it subsequent to the ones on my site so it is not in evidence there.


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Mayniyak
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Nov 13, 2011 18:43 |  #11

To understand fisheye lenses better, read this:

http://www.unc.edu/~jo​hnsonc/Fisheye_csj.pdf (external link)




  
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bulldogg7
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Nov 13, 2011 18:56 |  #12

Anyone got a side by side of an 8mm fisheye and 8mm rectilinear?



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Snydremark
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Nov 13, 2011 19:29 |  #13

Interesting read; thanks for that :)


- Eric S.: My Birds/Wildlife (external link) (7D MkII/5D IV, Canon 10-22 f/3.5-4.5, Canon 24-105L f/4 IS, Canon 70-200L f/2.8 IS MkII, Canon 100-400L f/4.5-5.6 IS I/II)
"The easiest way to improve your photos is to adjust the loose nut between the shutter release and the ground."

  
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What makes a fisheye a "fisheye"?
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