I'm sure this has never been done before 😉 -- but since I received my Lawla 10mm MF lens for Canon RF and Kenko 2x TC today, I figured I'd do a quick and dirty comparison at the rectilinear and fisheye field of view. Sharing it here in case it's helpful for others to visualize what you get with each type of lens and extreme rectilinear lenses in the 10mm range.

 

All these images are taken with same setup I've been using recently to test strobes (and, indeed, are at F22, ISO 100 with an Ikelite DS230 firing at full power). Distance from camera to the front wall is 1.4m. 

 

First, the rectilinear lenses. 10mm, 14mm, 15mm, 16mm, 17mm, 20mm

 

 

There's a pretty obvious jump in coverage from 14mm to 10mm. The difference between 16mm, 15mm and 14mm is not so dramatic. 

 

Now for the fisheye lens, Canon 8-15mm, at 8mm, 15mm, and then 16mm (8mm + 2x TC). And each of those focal length de-fished using lens corrections in Lightroom.

 

 

 

If you're going to de-fish the fisheye, do it at 15mm, not 8. While you do get a wider angle of view defishing a circular fisheye, the loss of resolution at the edges is pretty extreme. At 15mm, the de-fished image is acceptable in quality dowscaled to 1500 pixel, at least for web/social media use.

 

The 15mm fisheye image de-fished is  has a wider field of view than 14mm rectilinear - but closer to the 14mm  field of view than the 10mm rectilinear.

 

At the opposite end of the spectrum, here is the fisheye + 2x TC at 30mm  between the 28mm and 30mm rectilinear. They're very close -- I guess basically same as a 29mm rectilinear lens. Note that the rectilinear is marginally narrower horizontally but wider vertically. At 30mm, the fisheye only shows a mild amount of fisheye distortion. 

 

 

And here is the 30mm fisheye de-fished next to the 30mm rectilinear. Not much between them in terms of angle of view.

 

 

My conclusion is that the fisheye lens at longer focal length converges on the same angle of view as a rectilinear lens. This is especially once you de-fish it. 

 

Further, the 8-15mm + 2x TC combo gives has a very versatile range. It goes from a diagonal angle of view of 170 degrees at 16mm and 73 degrees at 30mm. That's very similar to the 170-74 degree angle of view Nauticam advertises for the FCP + Sony 28-60 combo. 

 

I'll take some shots with my WWL-C and 24-50 lens to see how the Nauticam conversion lenses fit into the bigger picture. 

 

 

Edited June 19, 20241 yr by DreiFish
Reducing image size to try to condense the post.

Here are the results with the WWL-C (in air.. perhaps it's a bit more zoomed in in water?)

 

At the wide end (24mm on the base lens), Nauticam rates it as similar to a 10mm rectilinear lens, and it sorta is. Same horizontal field of view, but the rectilinear lens has a taller vertical field of view.

 

 

Zoomed all the way (50mm on the base lens), it closely matches the field of view of the 35mm rectilinear lens. This is despite Nauticam stating it should behave more like a 21mm lens. 

 

 

So I'd say it's a bit more versatile than the 14-35mm lens, if you can live with the barrel distortion.

This should be a pinned article or something.

On 6/20/2024 at 1:22 PM, DreiFish said:

Here are the results with the WWL-C (in air.. perhaps it's a bit more zoomed in in water?)

 

At the wide end (24mm on the base lens), Nauticam rates it as similar to a 10mm rectilinear lens, and it sorta is. Same horizontal field of view, but the rectilinear lens has a taller vertical field of view.

 

 

Zoomed all the way (50mm on the base lens), it closely matches the field of view of the 35mm rectilinear lens. This is despite Nauticam stating it should behave more like a 21mm lens. 

 

 

So I'd say it's a bit more versatile than the 14-35mm lens, if you can live with the barrel distortion.

 

You can just take a constant zoom ratio (50/24 * 10 = 21) but that doesn't hold between fisheye projections and rectilinear ones.  I did some calculations and it appears that the WWL-C follows something close to a stereographic fisheye projection and you can calculate horizontal and vertical field from that:

 

What Nauticam quotes is a 130- 72° diagonal field which is equivalent to the diagonal field of 10-30mm lens, if you compare the horizontal fields it matches the field of a 12.2 - 31mm lens with a slightly smaller vertical field. 

@DreiFish you are such a darling! Many thanks for putting the time + brain + energy in this.

 

I have one more question:

 

Will a 1.4x TC show some black vignetting on the Canon 8-15 Fisheye @ 8mm ?
 

Maybe somebody owning a canon fullframe body with the above + EF-RF adapter, can report back on this. 💙

 

I am thinking about simply traveling with two teleconverters in the future and selling my Sigma 15mm Fisheye Lens to get a used Canon FE Zoom.

On 8/12/2024 at 2:36 AM, Adventurer said:

@DreiFish you are such a darling! Many thanks for putting the time + brain + energy in this.

 

I have one more question:

 

Will a 1.4x TC show some black vignetting on the Canon 8-15 Fisheye @ 8mm ?
 

Maybe somebody owning a canon fullframe body with the above + EF-RF adapter, can report back on this. 💙

 

I am thinking about simply traveling with two teleconverters in the future and selling my Sigma 15mm Fisheye Lens to get a used Canon FE Zoom.

Hey Adventurer,

 

No, the 8-15 + 1.4x (or 2x for that matter) doesn't vignette by itself. Of course, you need to have the right extensions for your dome port.. shorter extension may somewhat vignette, but that's a function of the port and extensions, not the lens and TC. 

 

The Canon FE Zoom is one of the best wide angle options on both Canon and Sony full frame systems. Also for their crop bodies. And it works great (with no TC or with a focal reducer) on M4/3 systems as well.

 

On 8/13/2024 at 7:20 PM, DreiFish said:

No, the 8-15 + 1.4x (or 2x for that matter) doesn't vignette by itself.

It doesn't? I was under impression that 8-15mm + 1.4x TC vignettes when set wider than 11mm, and only 2x TC gets you the full zoom range.

 

That's not vignetting -- you're just using it wider than intended, so you're part of the way towards the circular fisheye, just not all the way there. It's the exact same effect you would have if using it without a TC on full frame wider than 15mm...

 

10 hours ago, Barmaglot said:

It doesn't? I was under impression that 8-15mm + 1.4x TC vignettes when set wider than 11mm, and only 2x TC gets you the full zoom range.

That's splitting some very fine hairs. Vignetting refers to the effect itself, not to its cause. The question was "Will a 1.4x TC show some black vignetting on the Canon 8-15 Fisheye @ 8mm ?", and your answer to this, "No, the 8-15 + 1.4x (or 2x for that matter) doesn't vignette by itself." is quite misleading, as shooting the 8-15mm @ 8mm with 1.4x TC will produce significant "black vignetting", whereas using a 2x TC won't.

5 hours ago, Barmaglot said:

That's splitting some very fine hairs. Vignetting refers to the effect itself, not to its cause. The question was "Will a 1.4x TC show some black vignetting on the Canon 8-15 Fisheye @ 8mm ?", and your answer to this, "No, the 8-15 + 1.4x (or 2x for that matter) doesn't vignette by itself." is quite misleading, as shooting the 8-15mm @ 8mm with 1.4x TC will produce significant "black vignetting", whereas using a 2x TC won't.

This is the correct "dictionary" definition of vignetting.  Probably best to clarify the cause when referring to this phenomenon as you can't "fix" this type of vignetting which is caused by the limited image circle of the lens, while classic vignetting can be solved possibly by changing extensions or in some cases removing the dome shade.

My fault not beeing a native speaker.

 

@Barmaglot was right and by now I have both TC on my desk. Sadly I was put onto the wrong track by @DreiFish answer.

 

There is black edges in the frame when just using a 1.4x TC.

 

I could have remembered or computed it myself, though.