Canon / Sigma 400 zoom

[SmartWombat]

Canon 100-400 L IS and Sigma EX 80-400 IS, two consecutive years at le Mans.
Perhaps not fair as the Sigma is on the 20D and Canon on the 1DmkIIN

[Photo-John]

The tighter, bottom one is the Sigma? Looks sharper to me. What are the exposure settings?

[SmartWombat]

Sorry John, can't remember, they're in the EXIF but PR isn't showing the images for me to check. I think the lack of sharpness with the Canon is my fault.

[SmartWombat]

Canon 1/320 f/5.6, Sigma 1/640 f/8

[SmartWombat]

Canon 1/500 f/8

[Photo-John]

I checked the EXIF and saw that the settings were very different. How's the auto focus on the Sigma? Is the continuous focus speed and accuracy ok?

[SmartWombat]

Sigma AF speed was the reason I replaced it the week after Le Mans with the Canon.
It didn't cope at Goodwood Festival of Speed where I was closer to the cars.
Fine on people in the top paddock though.