Fisheye lenses on APS/C/Crop sensors

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grwiffen

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Graham
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I have a Nikon D7000 and am looking for a new fisheye lens. Many people are suggesting a 10mm, either from Sigma, Nikon or Tokina (10-17) but as I already have a Sigma 10-20mm for landscape work, I don't see any difference.

Am I missing something here?

I am presuming to get a real fisheye on a crop sensor you need to go to 8mm or even lower. I have seen a 6.5mm offering 180degres of view.

Thoughts, suggestions or just comments are all welcome for this one please.

Thanks in advance.
 
The Nikon 10.5mm does pretty much a 180 field of view. You have to keep your elbows and feet out of frame!

I love mine, use it loads
 
With fish-eyes, normal focal lengths don't apply when it comes to field of view.

A true fish-eye sees a full 180 degrees of angle, sometimes measured corner to corner of a rectangular image, or across the diameter of a circular image.

As a rough guide, think 10mm-ish for crop sensor format, and 15mm-ish on full frame. That's ball park for most fisheyes.
 
Hoppy, I think your numbers are referring to frame filling fisheyes. My 8mm Sigma gives a full circular image on FF and crops it slightly at top and bottom on a Nikon crop. The same lens might also be cropped slightly into the side on Canon crop bodies.

The major difference between fisheyes and UWAs is the distortion correction the latter do - your 10-20 gives relatively straight lines at the edges while a fisheye won't!

Here's a FF fisheye image, note how the straight lines of the building are distorted (the steps in the foreground are curved and inspired the shot!)
8026090988_3e1a67fb88_c.jpg


Here's a UWA shot of the same building shot at 12mm using a Sigma 12-24, note the straight lines of the building. The perspective exaggeration is a result of the laws of physics and can (if wanted) be "corrected" in PP.
8026091040_95b4112a6b_c.jpg


This final shot approximates the cropping a Dx sensor will apply to an 8mm image. This one was actually shot using a dedicated film camera but the effect is close enough for illustration purposes!
2517594565_d3d34b41a6.jpg


Irrelevant to this thread but of possible interest are these 2 - the captions on the pics are self explanatory. With thanks to Yv for the brief loan of the lens!
4050193420_526824ab9e.jpg

4050193432_c3c925124a.jpg
 
Fisheye per the same focal length as rectilinear offers a wider field of view. The effect means central objects appear the same as a rectilinear lens but the more curved edge areas show more width.

You'll "see" far more width on a 10mm FE than a 10mm rectilinear.

Edit:- Here we go, quick patio door test.

The LEFT has 10mm on a Tokina 10-17 FE and the RIGHT is 10mm on a Canon 10-22mm rectilinear

10mm-resize.PNG


Both photos taken from an identical spot with an identical centre aiming point. APS-C format Canon 550D.
 
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Gnirts, thats great, that comparison is what I needed to understand and see.

I thought the 10mm would be the same, but as you have clearly shown, its not. Brilliant.
 
Probably worth noting the difference gets less pronounced as you zoom in.

Same image below with both lenses set to 17mm. Tokina FE left, Canon 10-22 on right. Centre point for both the house window.

17mm-resize.PNG


I wouldn't really ever use a fisheye for landscapes - the curved effect is a novtly only value (hence the 10-22). I use the FE underwater because there are very few if any straight lines so you dont notice and its got a VERY close focus distance so make Close Focus Wide Angle possible.

You CAN right lens profile correction in lightroom/PS on a FE image but you lose some of the width then by definition.
 
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