I’m not sure if the optical stabilizer is working in my new Sigma 100-400mm C, as the viewfinder image looks quite jumpy. Is this normal? John Baxter
Jason says… I like the Sigma 100-400m f/5-6.3 DG OS HSM. It packs a lot of performance into a small and lightweight build, and is great value at £699/$699. The optical stabilizer has two switchable modes for static and panning shots but, by default, the action of the stabilizer is moderate for the viewfinder. Stabilization is only fully applied during exposures, when the viewfinder image is blanked. You can increase or decrease the amount of stabilization visible in the viewfinder, using one or both of the switchable Custom settings. You can also alter the autofocus speed and distance at which the autofocus range limiter works. To set up custom modes, as well as to apply autofocus fine-tuning and firmware updates, you’ll need a Sigma USB Dock. This costs £39/$59 and works with the company’s Global Vision (Art, Contemporary and Sport) lenses.