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I'm new to photography and I have questions about fisheye distortion adapters. I bought a Spiratone/Soligor/Kenko Fisheye lens adapter for my lens, because I didn't want to spent a lot just to try that effect.

I mount it with my first lens, a Nikon 18-105 with a 49-to-62 mm ring adapter step-up on my APSC Nikon dslr. With this configuration I, didn't have fisheye distortion in my photos (from 18mm to 105mm).

Why not?

First, I thought that was a problem with my non-full frame DSLR, but I seen some photos with this adapter on a APS-C camera. Could it be the 18-105 lens?

Now I have a Nikon 35mm 1.8G. If I buy the right adapter ring, will I have the fisheye distortion in my photos with this lens?

Thank you very much

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    \$\begingroup\$ You don't need an adapter to try it on the 35mm, just hold it over the lens and try it! \$\endgroup\$
    – Digital Lightcraft
    Feb 26, 2014 at 16:21
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    \$\begingroup\$ Since you are using an adapter ring to adapt the fisheye (from I presume 62mm) to the lens (42mm), you are effectively cutting out a LOT of the highly oblique angle light. A fisheye lens is designed to gather rays of light from up to 180°, and focus those onto the sensor. Since you are downgrading your fisheye element to a much smaller diameter, any part of the fisheye that extends beyond the filter ring of your lens is effectively wasted FoV. You should be using a fisheye element that is specifically designed for 42mm. \$\endgroup\$
    – jrista
    Feb 27, 2014 at 3:50
  • \$\begingroup\$ @DarkcatStudios: yeah, I could try it :D jrista, and darkcatstudios: the fisheye adapter is 49mm filter thread, my 35mm is 52mm filter thread. With adapter I mean ring adapter for filter thread. Thank you for the answers. \$\endgroup\$
    – Tenaciousd93
    Feb 27, 2014 at 7:50

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Let's think about what's happening here. The adapter essentially reduces the focal length by about 60%, giving a wider field of view. It's an oversimplification, but let's stick with it for brevity.

Say you have a prime lens with a fixed focal length of 50mm. With the adapter in place, it now has the field of view equivalent to a 20mm lens.

With your lens, that 18mm lens has a field of view of around an 8mm. Definitely fisheye territory.

However, you also have to factor in the crop sensor. This increases the effective focal length by about 50%. Your 8mm? That's now 12mm. Wide angle, certainly, but perhaps not the extreme fisheye distortion you expect.

As you zoom in, the effect will decrease. There's literally no point using these adaptors at anything other than the first few millimetres of the lens since you gain nothing you can't do with your lens normally, while sacrificing image quality.

With the 35mm lens, you will land up with the equivalent of around 21mm focal length. So to directly answer your question: No, it is not going to give you any fisheye distortion on that lens.

I have presumed the one you bought is the 0.43x converter, which is the first one a cursory Google search turns up. To work out the effective focal length, you take the lens focal length, multiply it by whatever magnification it is, and then multiply it by 1.5 to take the crop sensor into account. Again, oversimplifying it a bit, but essentially the lower the number you get, the wider the field of view becomes - you will need to be sub-10mm to get close to the fisheye effect you want.

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    \$\begingroup\$ All true, however it's also worth noting that fisheye != wide angle. Ultra wides can have a lot of perspective distortion without actually being a fisheye lens. \$\endgroup\$
    – Dan Wolfgang
    Feb 26, 2014 at 17:02
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    \$\begingroup\$ Less than 10mm is not required to see a fisheye effect. A quick search shows fisheye lenses in the 4.5-17mm range. Fisheye lenses are a special optical design, not a measure of focal length. \$\endgroup\$
    – Dan Wolfgang
    Feb 26, 2014 at 20:06
  • \$\begingroup\$ Both comments noted. Reading the question, it sounds to me like the OP isn't terribly interested into going into all the technicalities of what makes a fisheye lens a fisheye lens - he just wants to get that effect. I did say it was an oversimplification! :) \$\endgroup\$
    – Thomas Bisset
    Feb 26, 2014 at 20:31
  • \$\begingroup\$ Thank you all for answers me, now I understand more what happens with this adapter. @ThomasBisset: My fisheye adapter is a Soligor 0.15x fisheye adapter, see google for a example. So, if I understand correctly, 35mm lens with 0.15x magnification and 1,5 crop factor I would have around 8mm. Am I right? What about 18-105 at 18mm with 0.15x and 1.5 crop factor (results around 4mm)? Mmmh, the fisheye adapter is 49mm filter thread, my 35mm is 52mm filter thread and the 18-105 is 67mm. Thanks \$\endgroup\$
    – Tenaciousd93
    Feb 27, 2014 at 7:47
  • \$\begingroup\$ Sounds about right. Presumably it is giving you the effect you want at the widest end of the lens? \$\endgroup\$
    – Thomas Bisset
    Feb 27, 2014 at 14:11

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