Fisheye defishing and comparing

Started Apr 27, 2013 | Discussions thread
micksh6
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Re: Fisheye defishing and comparing
In reply to CrisPhoto, Apr 28, 2013

CrisPhoto wrote:

My current opinion is like this:
  • The fisheye is very sharp
  • It can be used as a UWA and the sharpness is acceptable like 10MPixels

I disagree that Samyang fisheye is like 10MP sharp lens. It depends on how you count megapixels. I hope you didn't start evaluating lens sharpness based on that recent DxO lens rating "invention".

Samyang fisheye outresolves 16MP sensor in center area, and this center area is large, 2/3 - 3/4 of the frame, perhaps. With exception of Olympus 75mm F1.8 and probably manual Voigtlanders it would be hard to find a lens that would be visibly sharper in that area.

As for the corners - it depends on how you process them. I use Panini projection almost exclusively because I find straight vertical lines curved to circular ugly, but I vary degree of defishing. With Fisheye Hemi plugin (which I run in Paint Shop Pro) you can apply "cropped" fisheye correction that doesn't fully make vertical lines straight but makes a good compromise in many cases. And you can apply "cropped" twice, it will defish a bit less than full frame Panini defishing. It's especially useful when photographing people close to the edge of fisheye. Full Panini projection defishing will make people fat, stretched and distorted. Partial Panini will do much better, people may look a bit bend but still natural.

You can replicate this in Hugin by entering longer focal length for fisheye - try 10-12mm instead of 7.5mm. Fisheye Hemi is much faster to work with than Hugin. Side effect of less defishing - corners will be sharper.

Don't know what you consider medium size prints. I printed several fisheye photos from the thread below at 12x18" and they are very sharp when looking close.
http://www.dpreview.com/forums/post/50922832

I would really like to hear your feedback or your experiences regarding the fisheye versatility/defishing thing.

Regarding versatility - Paint Shop Pro that I mentioned also has built-in rectilinear fisheye correction. It's parametrized, so you can specify the degree of rectilinearity you need. It also enlarges pictures when defishing so no resolution is lost in center.

Full rectilinear projection would make 1:2.4 cinema wide ratio out of 4:3 so it never makes sense. For indoor shots like real estate listings it makes sense to apply partial rectilinear defishing, then straighten vertical lines with partial Panini projection.

If you have time, combining these and experimenting can be fun. And there is also adaptive wide angle filter in Photoshop CS6.

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