Sigma 18-35mm f/1.8 DC HSM Art Lens Aperture Comparison
The 18mm and 35mm images presented below were captured from the same camera positon, approximately 6' (1.8m) away from the focused-on foreground tree. In addition to comparing the look created by the various tested apertures, the angle of view afforded by these two focal lengths can also be compared. These images were captured with a Canon EOS 60D.
The 35mm examples, with their narrower angle of view, have a more-diffusely-blurred background than the 18mm examples.
Narrowing the aperture (selecting a higher-numbered aperture setting), results in more depth of field. The downside to selecting a very narrow aperture (narrower than the camera's DLA) is the effect of diffraction, causing increasingly less-sharp results across the frame as the lens opening is redcuced.
Note the difference in background blur possible from the max aperture of the lens you have or are considering compared to the Sigma 18-35mm f/1.8 DC HSM Art Lens' capability.
Being a "DC" lens, the Sigma 18-35 f/1.8 is designed to cover the image circle of APS-C format cameras. But, this lens mounts and functions on full frame camera models. Requiring a larger image circle for full sensor coverage, these cameras will show vignetting when the 18-35 is mounted to them. But, perhaps not as much vignetting as you might expect.
Here are sample images captured on a Canon EOS 5D Mark III:
Obviously and as-expected, vignetting is worse on the wide end of the focal length range. Also as-expected is that the hood increases the vignetting at the wide end.
The with-hood vs. without-hood samples clearly show the protection added by the hood. And the benefit of the petal-shaped hood can easily be seen.
Back to the Sigma 18-35mm f/1.8 DC HSM Art Lens Review.