Canon 8-15 mm Vs Tokina 10-17 mm

Two fisheye zoom lenses at fully opened aperture (f/4).

Foreword:

The field of a fisheye lens is not flat. As a matter of fact the image is being recorded on a "flat" film or digital sensor is sharpest for objects that more or less on a spherical surface situated in the depth of field. The smaller is this spher, the truest is this rule.The camera sensor is near the center of the sphere.

In other word and in order to better imentally visualize the facts: the fisheye lens is perfectly able to project the planar image of a (transparent) photograpic slide on a projection hemispherical (dome) screen and the projected image is then quite sharp along 180 degrees of field of view! That feat is impossible to perform with a regular rectilinear (a.k.a. "without distortion") lens that is optimized in order to produce a "flat" field.

Subject

The Tokina 10-17 mm F3.5-4 was the only zoom fisheye for DSLR that was commercially avalaible before introduction of the new Canon EF 8-15 mm F4 "L" lens at the end of July 2011. We shall compare the final Image Quality of this new Canon lens with its direct rival when mounted on a Canon EOS 5D Mark2. The Tokina lens was designed originally (by Ashi-Pentax) to fit on APS-C (cropped) sensor sized DSLR. To fully fit on a Canon fulframe camera (EOS 5D Mk2), the sun hood was completely "shaved" in order to free the field of view from its obstruction in the image.

Shooting is done at f/4 for all the images. While f/3.5 @ 10 mm is possible on the Tokina on the lower end of the focal lengths range, that's however the fully opened stop setting shared by both lenses from 12 mm up to 15 mm of focal length.

When shooting outdoor panoramas one would generally set the lens at the hyperfocal. After having shot images from the same location at three salient focal lengths (10 mm, 12 mm and 15 mm), we shall compare cropped parts of the images from these to comparable lenses.

These conditions lead to six cases and two images for each case. The two images are got from two orthogonal orientations for shooting at the object (a dartboard fixed on the trunk of a poplar tree):

Target is on the lens axis: the dartboard is viewed at the center of the image. The camera is 34 deg rolled.
After 90 degrees of rotation of the camera around a vertical axis, the target is near the edge of the coverage (here at the corner of the image @15 mm of focal length)

All the images have been converted and cropped in ACR 5.6. Llighing radial fall-off (.a.k.a Vignetting) and chromatic aberration were corrected or removed as far as possible No intentional sharpening was applied. The resulting final cropped sample images are presented in 100% magnificationin the following table:

 

Canon 8-15 mm @f/4 on EOS 5D2

Tokina (shaved) 10-17mm @f/4 on EOS 5D2

   

Distance of focus set at 1.8 m for all photographies on this table

Focal length set at 15 mm

(Hyperfocal distance = 1.8 meters)

 

 

Object is on-axis at 1.8 meter from the sensor plane

 

 

 

After rotatiion of camera, the object is 90 deg off-axis and at 1.8 meter from the lens axis

Focal length set at 12 mm

(Hyperfocal distance = 1.8 meters)

 

 

Object is on-axis at 1.8 meter from the sensor plane

 

After rotatiion of camera, the object is 90 deg off-axis and at 1.8 meter from the lens axis

Focal length set at 10 mm

(Hyperfocal distance = 1.8 meters)

 

Object is on-axis at 1.8 meter from the sensor plane

 

After rotatiion of camera, the object is 90 deg off-axis and at 1.8 meter from the lens axis

 

 

Observations:

The New Canon lens is awesome. It outperforms the Tokina in all cases and especially on the edge of coverage...

While they have barely decent sharpness at 12 mm, the images at the edge of the fisheye images by the Tokina suffer from strong sagtal and transversal astigmatism: they have poor contrast, they are blurred and together these defects result in a smaller (spherical) depth of field.