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Comparison of rectilinear versus rectilinearized 111 hAOV of
    Sigma AF 12-24 mm f/4.5-5.6 EX DG zoom @ 12 mm
    Canon EF 15 mm f/2.8 fisheye and 
    Sigma AF 8 mm f/4.0 EX fisheye
on a Canon EOS 5D

The Sigma AF 12-24 mm f:4.5-5.6 EX DG zoom provides the widest possible rectilinear field of view on a 24x36 mm camera, like the Canon EOS 5D, or a 1.3x cropping camera, like the EOS 1D-series. At 12 mm setting it provides an impressive 292 percent hFOV or 111 hAOV.

The only other way to get an equally wide AOV is to use a fisheye lens. Such images may be remapped to a rectilinear projection using software like RectFish. 

This is a comparison of the image quality of the Sigma at the 12 mm setting to that of the Canon EF 15 mm f/2.8 and  Sigma AF 8 mm f/4.0 EX fisheye lenses when rectilinearized using the same hAOV as provided by the zoom at 12 mm on a "full frame" Canon EOS 5D.

The lenses was tested at different f-stops with the camera set at ISO 100. 

 

The photographed scene: 
The Greenhouse in Copenhagen Botanical Gardens



Sigma AF 12-24 EX @ 12 mm and f/8


Canon EF 15 mm f/2.8 fisheye


Canon EF 15 mm fisheye rectilinearized


Sigma AF 8 mm f/4.0 fisheye


Sigma AF 8 mm fisheye rectilinearized

 

The camera was tripod mounted. Images were captured as RAW and converted to 24 bit TIFF files using DPP 3.0.0.3. Sharpness was set to 0 (no sharpening) and no other post processing has been applied to the images. The fisheye images were then remapped to a rectilinear projection using RectFish. Finally 200x200 pixel crops were excised from the centre, midway and periphery and saved as TIFF prior to conversion as JPEG files.

The comparisons

Centre - APS-C edge - Edge - Summary