Sigma 10-20mm F3.5 vs F4.0-5.6

Image Quality: Sharpness

With an ultra-wide angle lens, you need to consider several image factors that are unique to the category. The image factors that we will be examining are: sharpness, distortion, vignetting, flare, chromatic aberration, and angle of view.

For sharpness testing, we used an Edmund Resolution Power Chart and field tests. The chart was originally designed to determine the maximum resolving power of an optical instrument. We’re not using the chart as it was originally intended, which was to distinguish the last group of visual lines to be distinguished. In this review, the purpose of the chart is to compare one lens to another. The chart allows the viewer an apple to apple comparison of different lenses using a standard measurement.

For the field sharpness testing a typical architectural setting was selected that offered a variety of elements. The camera was placed on a tripod to minimize changing either the camera location or settings.

Conclusion

The results of the Edmund Resolution Power Chart were interesting. Initially, the Sigma 10-20mm F/4-5.6 slightly out preformed the Sigma 10-20mm F/3.5. The field sharpness results were a little different. The Sigma 10-20mm f/3.5 was clearly sharper than the F/4.0-5.6 lens.

I should note that the copy of the Sigma 10-20 F/4-5.6 that I received did not accurately focus on the resolution chart and I had to manually focus the lens. I’m not sure if the lens had a front/back focus problem but it can be corrected in the custom settings of the camera.