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 220.127.116.11. 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.