15mm Full Frame Fisheye vs. 16-35mm at the wide end

BackdoorArts

Senior Member
After using my Rokinon 8mm this past weekend I'm longing for something like that for my D600 without losing all the MP's on a DX crop. It seems that the Sigma 15mm and the Nikon 16mm Fisheyes are my only option. Each claim "180 degree view on the diagonal", which I understand (bottom right to top left is a 180 degree angle of view), but what I haven't been able to ascertain is just how many degrees that is left to right.

Here's a link to an angle of view comparison on the Sigma site, and while it states that the 15mm fisheye has 180 degrees view, it looks an awful lot like the field of view from the 17mm lens directly underneath, which sports 103.7 degrees. So the real difference seems to be only the lines and distortion and not so much the L-to-R angle of view. If that's the case then the 107 degrees I get with my 16-35mm is actually wider, so I gain very little.

Does anyone here have any experience with the Sigma or Nikon FX Fisheyes? If so, what are your thoughts? I'd love to get something that produces photos closer to my Rokinon (which is equivalent to a 12mm), but if I have to I'll settle for using that with the D800 at 16MPs.
 

stmv

Senior Member
the Nikkor 16mm is tiny but does distort,, I have an old 15 mm 3.5 ,, a real gem,, and still out there. I love the old 15 mm lens.
 

BackdoorArts

Senior Member
Sounds like an excuse to buy the 14-24 to me.

Nah. Way too much money for an extra 2mm. ;) Heck, $600 is more than I want to spend for less than 10 degrees additional view if that's all I get with the Sigma Fisheye. I need to find some place that has it so I can compare.
 

Steve B

Senior Member
With ultra wide angle lenses there are three different types. Rectilinear (most wide angle zooms fall into this category), full frame fisheye (diagonal FOV of 180), circular fisheye (180 FOV in all directions but circular image). Just google "rectilinear vs fisheye lenses" and you will find a lot of info. On the Sigma AOV comparison it looks like the 15mm is a full frame fisheye and the 17mm is a rectilinear lens. I've had experience with full frame fisheye lenses on 4/3 cameras (Olympus 8mm) but not on DX or FX yet.
Sigma makes a circular fisheye for FX: http://www.bhphotovideo.com/c/product/440661-REG/Sigma_485306_8mm_f_3_5_EX_DG.html
 
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480sparky

Senior Member
Simple math will tell you the FOV across the long end of the sensor.

The lens projects 180° from corner to corner. Now, what is the dimension of the sensor corner to corner? From Nikons website, the D600's sensor is 35.9 mm x 24.0 mm.

So the Pythagorean Theorem (a² + b² = c²) means 35.9² + 24² = c². 1288.81 + 576 = 1864.81. Square root of 1864.81 is 42.183.

That means there's 4.267° per mm. Since the sensor is 35.9mm wide, 35.9 X 4.267 = 153°.
 

BackdoorArts

Senior Member
I get the math, but that assumes the non-warping of space, which you get with a Fisheye. So while I understand that in theory it should be 153 degrees I was bothered by what I saw as something significantly less than that in the linked photo comparison where the L-to-R field of view was significantly less than 153 degrees, which is why I'm raising the question and asking about practical experience with these lenses. Obviously the photograph could be wrong.

I've done a lot of googling and reading and from the examples I'm seeing of shots with both the Nikon and the Sigma fisheyes it would seem that what I'd get is more effect than field of view, which is really what I want. I wish I was free to hit the PhotoPlus show this week in NYC to check them out in person, but alas that's not going to happen.
 

BackdoorArts

Senior Member
OK, a picture is worth 1000 words, right...

angleofview_poster_new_0.jpg


Here are the 4 widest angle lenses in the Sigma line from the photo I was referencing. Ignoring the circle fisheye, if you compare the 15mm Fisheye, 12mm and 17mm you can clearly see that the 15mm Fisheye with "180 degree view" is barely wider than the 17mm at 103.7 degrees (note the grey box excluding the things in the 15mm photo not in the 17mm photo), and definitely narrower than the 122 degrees from the 12mm (shaded area in the 12mm photo denotes subject matter not found in the 15mm photo). So while they're calling it a 180 degree full frame fisheye, the truth is that the field of view seems to be consistent with a 15mm lens and not the mathematically derived 150+ degrees you'd expect if you're getting 180 degrees on the diagonal.

Or the example photo is just wrong.
 

480sparky

Senior Member
OK, a picture is worth 1000 words, right...

View attachment 56864

Here are the 4 widest angle lenses in the Sigma line from the photo I was referencing. Ignoring the circle fisheye, if you compare the 15mm Fisheye, 12mm and 17mm you can clearly see that the 15mm Fisheye with "180 degree view" is barely wider than the 17mm at 103.7 degrees (note the grey box excluding the things in the 15mm photo not in the 17mm photo), and definitely narrower than the 122 degrees from the 12mm (shaded area in the 12mm photo denotes subject matter not found in the 15mm photo). So while they're calling it a 180 degree full frame fisheye, the truth is that the field of view seems to be consistent with a 15mm lens and not the mathematically derived 150+ degrees you'd expect if you're getting 180 degrees on the diagonal.

Or the example photo is just wrong.

The FOV of one lens at a given focal length doesn't mean a smaller focal length is automatically a wider FOV. The 12mm in your example is 122°. I remember owning a 17mm fisheye, which was 180°. So focal length isn't always a linear correlation to FOV.
 

BackdoorArts

Senior Member
I get all that. What I'm saying is that there's no way any part of the photo associated with the 15mm Fisheye shows a 180 degree field of view, particularly when you compare it to the others.
 

480sparky

Senior Member
I get all that. What I'm saying is that there's no way any part of the photo associated with the 15mm Fisheye shows a 180 degree field of view, particularly when you compare it to the others.

I guess I don't understand what you're getting at. I was simply addressing the question:

........ but what I haven't been able to ascertain is just how many degrees that is left to right. .........
 

BackdoorArts

Senior Member
Actually, this was my question...

Does anyone here have any experience with the Sigma or Nikon FX Fisheyes? If so, what are your thoughts? I'd love to get something that produces photos closer to my Rokinon (which is equivalent to a 12mm), but if I have to I'll settle for using that with the D800 at 16MPs.

...and no one has bothered to address that with any practical information as yet.
 
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