Fisheye FOV on crop body

[rjpierrard]

<p>Hello,</p>

<p>I'm wondering how to calculate the FOV of a fisheye lens as you introduce crop factor.<br />I have a giant spreadsheet that will calculate a rectilinear lens FOV, but it obviously doesn't work with fisheye lenses.</p>

<p>I'm looking at two options here, FX->DX (eg using a Nikon 16/2.8), or DX->4/3 (eg the Pro-Optic 8/3.5).<br />Both are rated at 180* without a crop factor, but as I'm working on designing a multi-format setup, I'm wondering what the options for fisheyes are.</p>

<p>Also, I'm wondering if it's possible to put an extension tube inbetween a fisheye lens and the body and still be able to use it (as a functional macro lens with wide FOV). I've tried it with the Tokina 11-16/2.8 on my D90, but that setup didn't work out. </p>

<p>Thanks!</p>

[craigd]

<p>You would have to know what projection a particular fisheye lens uses to calculate its exact angle of view on a DX or Micro Four Thirds body. Not all fisheyes are exactly the same. See this article at Wikipedia and scroll down to "Mapping Function":</p>

<p><a href="http://en.wikipedia.org/wiki/Fisheye_lens">http://en.wikipedia.org/wiki/Fisheye_lens</a></p>

<p>I have never tried using an extension tube with a zoom lens, but I'm not sure the results would always be what you expect. I would think it should work with a prime fisheye, but it would have to be a fairly short extension tube since fisheye lenses have very short focal lengths.</p>

[rjpierrard]

<p>I use my extension tube quite frequently on the 28-80 I've got, and it works beautifully; the tube itself is I think 20mm or so.</p>

<p>Thanks for the link - it has a formula on it that gives 170* for a 16mm fisheye on FX, but I can't seem to get it to work on DX: 8mm is given as 251*.</p>

[Dieter Schaefer]

<p>Provided I did the calculations correctly, the 16/2.8 - an equisolid fisheye I believe - will have a diagonal FOV of 107 degrees on DX and 82 degrees for 4/3. <br>

The Pro-Optic 8mm - a stereographic fisheye - would have a diagonal FOV of about 140 degrees on 4/3.</p>

[hans_janssen]

<p>A FX FE used on a DX camera is only usefull if you correct it to rectalinear in PP. You don't have the FE effect on a DX camera only the effect of a very bad corrected UWA lens.</p>

[JosvanEekelen]

<p>I'm sure some formulas can be found on the internet to calculate the effect of an extension tube with a fisheye lens but expect the focus to be very close to the lens, even inside the lens. OK for pictures of bugs inside the lens but of no practical use.<br>

I couldn't resist testing it with a Peleng 8 mm fisheye, Canon 12 mm extension tube on a EOS 10D. It's not possible to get anything in focus. Test completed succesfully: conclusion is that this combination has no use.</p>

[User_276104]

<p>When I got a D2x I was curious what my 16mm fisheye would do on it. It doesn't look wide at all, and still shows some curvature.</p><div></div>

[eric_arnold]

<p>IMO you're better off with a DX fisheye lens on a DX camera. if you're shooting nikon, i would go ahead and get the 10.5 fisheye. i have a 15mm sigma FE but on DX it's just a distorted 22.5mm lens. much better on FX.</p>

[rjpierrard]

<p>Alright, thanks</p>

[User_276104]

<p>I don't know if it's because of the optical formula (I'm making things up here), but the standard 1.5x crop factor doesn't seem to apply to FF fisheye lenses on DX cameras. My Nikon 17-35mm provided a wider view than the 16mm fisheye on my D2x.</p>

[john_hinkey]

<p>Yes, my 16/3.5 FE (170 deg. on FX) gives about a 18mm FOV on DX as I recall. I used my 16mm FE on my DX camera all the time because there was no other lens as small/light that gives that FOV on DX. Yes the distortion is not great, but for many subjects it's just fine. After some light distortion correction it became a roughly 20mm equivalent FOV on FX, which is plenty wide for many instances.</p>

<p>John</p>

[sem_svizec]

<p>> Also, I'm wondering if it's possible to put an extension tube inbetween a fisheye lens and the body and still be able to use it (as a functional macro lens with wide FOV). I've tried it with the Tokina 11-16/2.8 on my D90, but that setup didn't work out. <br>

Try handholding the lens unmounted directly in front of the body ;) <br>

The shortest Nikon extension tube is the old K1 ring from the K1-K5 set, 5.6mm. Absolutely manual, no aperture coupling. Fits modern cameras fine, but is very tight on the lens electrical contacts (one should shave off a bit of brass there). </p>

[john_hinkey]

<blockquote>

<p>Also, I'm wondering if it's possible to put an extension tube inbetween a fisheye lens and the body and still be able to use it (as a functional macro lens with wide FOV). I've tried it with the Tokina 11-16/2.8 on my D90, but that setup didn't work out.</p>

</blockquote>

<p>You'd have to use the absolute thinnest extension tube - I've never tried it with my 16/3.5 AI on my D700 - I have the PK-11a. Perhaps I'll try it this afternoon and report back.</p>