interesting fact about the Sony UWA/fisheye converters

willang77 wrote:

I was under the impression that usually, converters that fits on top of a lens will change the f-stop by at least 1 stop or more.

You have it confused with tele-converters, which fit between the lens and the body.

I think that you mean that the fish eye lens reaches a 180 degree in the long direction (horizontal typically) of the sensor?

It doesn't do that, and I doubt that the Nikon does it either. Maybe on FF, but this is an APS-C sensors.

I forgot the angle of view - it is on the Sony website. The adapter converts the 16mm to a 10mm fish eye, it sounds very close to your Nikon.

mynakedsoda wrote:

Does anyone who owns this know if it turns the lens into a true horizontal fisheye? I know it states 180 degrees but the images look odd to me that I can find. My basis for comparison is the Nikon 10.5mm horizontal fisheye I own. I tend to use it for people shots mainly for effect or inside or on park equipment. I know I could simply use it on the Nex with an adapter but the Sony converter would take up much less space in a camera bag and seems pretty cheap.

When they talk about a full frame fisheye like the Nikon 10.5 having a 180 degree field of view they are talking about the diagonal field of view, not horizontal

I would assume the Sony converter is measured the same way.

look here:

http://imaging.nikon.com/lineup/lens/specoalpurpose/fisheye/af_dx_fisheye105mmf_28g_ed/index.htm

"Full-frame fisheye images with a picture angle of 180° (diagonal)"

From what I can find in the specifications both the Nikon 10.5 fisheye and the NEX fisheye conversion attachment are full frame fisheyes and as such both are roughly equal to a 15mm fisheye lens on a full frame camera. They also both cover approximately the same diagonal field of view of 180 degrees

Where they could be very different is in how the image is mapped on the sensor

there are many different ways to do this mapping and if it is not done the same way in both lenses the images they produce would not look the same and the way things away from the center of the frame curved would be different. Perhaps this is the difference you are seeing.

look here
http://en.wikipedia.org/wiki/Fisheye_lens#Mapping_function

you can also learn about fisheye lenses field of view and mapping here
http://www.bobatkins.com/photography/technical/field_of_view.html

I do not have the NEX conversion lens so I can not directly compare it to my 10.5, but I hope you find this information helpful

mynakedsoda wrote:

edwardaneal wrote:

When they talk about a full frame fisheye like the Nikon 10.5 having a 180 degree field of view they are talking about the diagonal field of view, not horizontal

I would assume the Sony converter is measured the same way.

look here:

http://imaging.nikon.com/lineup/lens/specoalpurpose/fisheye/af_dx_fisheye105mmf_28g_ed/index.htm

"Full-frame fisheye images with a picture angle of 180° (diagonal)"

I own the 10.5 and it is a true horizontal fisheye on my D100 or D200 cameras. As you know they both use 1.5 crop sensors. Meaning you can move your finger to the edge of the lens on the horizontal side and it will appear in your image. The pictures I'm seeing with the Sony Converter don't have the same look I'm used to seeing with my 10.5 thus the reason I'm asking.

Then it is probably the same - see pic below

You can see my finger at the right hand side. This was 'beside' the lens, not in front.

Also - if you follow the pink concrete inlay (bottom) you can follow the curvature. You can see that both sides (180degree) are in the view.

As I understand it now - the fisheye forms a full circle on FF.

On DX (or APS-C) this is cropped to the size of the sensor, hence the different view.

The lenses can follow different mapping curves - you have to view them side by side, but at a first glance I'd say that they are very similar.

You can see that the scene forms a straight line in the second pic (taken from further away).

andrewD2 wrote:

Would you do me a big favour and email me a full size image of the stadium shot (or any shot showing corners really). I'm a big fisheye fan and really tempted by a nex C3. Have the minolta A mount 16mm FE and the canon 15mm FE.

Andrew

Try clicking on "Original"?

The file should be 6.6MB and measure 4592x3056 pixels (straight OOC).

If not, let me know -send me a PM - I will mail you original.