Handling
For testing purposes we used the Sigma 105mm lens on the Nikon D300S, D700 and D3100 DSLRs. Specified as a DG lens, it is designed for both full 35mm frame and APS-C sensor sizes.
The focal length is more suited to a full-frame sensor for standard close-up and portrait use, but as this becomes equivalent to a 157-167mm lens on the smaller APS-C sensor, it is roughly equivalent to the longer 150mm and 200mm macro lenses preferred by wildlife photographers.
As with most macro lenses the effective aperture is given by the camera, and at full 1:1 magnification it loses 2EV of light, giving an effective range of f/5.6 to f/45, compared to the f/2.8 to f/22 at infinity.
Image: The very shallow depth of field of the 105mm lens at 1:1 magnification. Nikon D300S, 5secs at f/22, ISO 200
The inclusion of an HSM (Hyper-Sonic Motor) makes it compatible with non-motor bodies from Nikon and leaves the autofocus near silent, although the stabilisation often lets out a faint ‘squawk’ when first engaged. This sounds a lot like a focus motor of old and could be enough to scare small animals at close range.
While focusing is fairly rapid, even when the change in distance is great, as with many macro lenses, if it misses the focus it takes a few seconds to go through the huge range from 0.312m to infinity, although this can be avoided by using the limiter.
The manual-focus ring is pleasant to operate and, while not that smooth, it still allows the fine and accurate adjustment needed to control close focusing.
