Sigma 100-300mm F4 EX DG IF APO A-mount lens review by polyglot
|polyglot#2475 date: Jun-25-2007|
flare control: 4
|ownership:||I own this lens|
|compared to:||M 70-210/4 beercan|
|price paid:||939USD (new)|
|positive:||Extremely sharp across the entire (APS-C) frame. Neutral to good rear bokeh. Indestructible.|
|negative:||Poor front bokeh with very evident axial colour in the donut-shaped highlights. Slow focus and tendency to hunt.|
|comment:||This lens is extremely sharp; it can easily out-resolve the A100 sensor at any aperture up to f/8, at which point diffraction becomes visible. Had no problems with metering.|
Colour is excellent inside the DOF and behind it. The only problem is evident axial colour in highlights in front of the DOF. It's only evident for very bright spots that have a lot of contrast with the background and typically only noticeable in 1:1 crops, you have to hunt for them on an 8x12.
Without the hood, flare can be a problem if sunlight hits the front element. The hood is large and works very well, so you need to make sure it's on.
This lens has a tendency to hunt, which can take a long time without HSM/SSM due to the big chunks of glass that have to move a long way.
Depth of field can be tiny (couple of cm) when operated wide open, which shows up any focusing inconsistency from the camera. I find that with AF-S or DMF modes, I get very accurate focus. AF-C though tends to be a little off, which is a problem because the error is so small that it is not visible in the viewfinder.
Another issue that it shows up on the camera is that the A100 (and perhaps all other SLRs with contrast/phase AF systems) can perceive that there is detail significant distances behind the subject, even though the subject is very nearly in focus. The camera therefore hunts out to infinity to try out the background focus then comes back in again before finally settling on approximately what it had before. It doesn't do this with backgrounds containing little detail - in those cases it snaps straight into focus.
Build quality is "like a tank". Distortion... it doesn't.
Update: tested with A700. Focusing accuracy & speed are definitely better. Quality is still good with the matched 1.4x TC, though you do need to stop down 1/3 of a stop to get perfect sharpness back again.