# Thread: ps vs fish eye lens

1. ## ps vs fish eye lens

all comments welcome. could someone also point out the noticeable difference between real fish eye lens and ps effect.

http://www.pbase.com/image/23196388

2. i take it you did that with ps?

3. A rectangular fisheye has a diagonal viewpoint of 180 degrees while a true fisheye has a true hemispheric 180 degree coverage. No rectilinear image can be converted to a true FE effect bcoz it's simply not wide enough - not enough information was captured in the first place.

That picture is nowhere near what a FE looks like.

4. thanks for the explanation, i understand better now.

5. Originally Posted by ST1100
A rectangular fisheye has a diagonal viewpoint of 180 degrees while a true fisheye has a true hemispheric 180 degree coverage. No rectilinear image can be converted to a true FE effect bcoz it's simply not wide enough - not enough information was captured in the first place.

That picture is nowhere near what a FE looks like.
One way around that would be to stitch a vertical and horizontal 180 degree panorama and convert that to a fisheye image.

6. i would imagine a wide angle of horizontal and vertical followed by massive cropping? most effects are possible with good ps skill. i am quite happy to go without a fish eye for now, wish list too long ....

7. Originally Posted by noblerot
i would imagine a wide angle of horizontal and vertical followed by massive cropping? most effects are possible with good ps skill. i am quite happy to go without a fish eye for now, wish list too long ....
It's not that simple. i think PS skills would be the last of your worries. You'd need SOLID mathematical foundation in geometry and transformations. (Ok, maybe not solid, but at least 'good'. At the very least, you'd need to de-distort the wide angles before stitch and re-distort to FE after stitching.) Unless someone else works out the parameters and posts online.

AFAIK, nobody's quite interested in rectilinear-to-fisheye conversion bcoz the rectilinear lenses costs at lot more than the fisheyes. There are conversions and tools to convert from FE to rlinear, though.

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