Re: Sigma APO or OS Lens

Bruce wrote:

All very interesting. However, we have two replies that concentrate
only on the focusing and anti-shake technology of these two Sigma
lenses.

Absolutely nothing was said about the optical quality, which was the
original poster's question. He said:

"I seek a affordable lens with the best quality at the 500 mm range."

So which lens offers the best quality at 500mm?


They offer comparable quality at 500mm. The 150-500mm has a more even coverage and a flatter field, sharper and slightly higher in contrast at 500mm. The 50-500mm performs better at short focal lengths - it's surprisingly good at 50mm, beating many midrange zooms.

There is a difference in price and in size and weight. Due to the OS system the 150-500mm is larger and heavier - both lenses weigh nearly 2 kilos, which is beyond the strap-hanging weight for safety (DSLR mounts can generally support up to 1 kilo, professional metal body models up to 1.5 kilos, without additional support for the lens). 1800-1900 grammes is just that bit over the limit.

At 500mm the 150-500mm is still the best choice despite the extra weight and bulk even without the OS. The non-OS lens is slightly lighter but exactly the same size, as Sigma used the same basic housing.

There is one other consideration I had forgotten to mention. The 150-500mm uses a type of internal focusing which alters the focal length more than the focusing on the 50-500mm, but is more parfocal. Thus, both lenses can manage the same size of image - 1:5.2, or 0.19X magnification - at 500mm. The 50-500mm does so at 3m distance, but the 150-500mm has to be 2.2m away to achieve this. That can make a big difference for small animal and bird photography with feeders/nestboxes/hides.

However, the 50-500mm must be refocused as you zoom. The minimum focus distance at 50mm is 1m (it would unusable as a 50mm if it was 3m, the minimum at 500mm). You can not zoom without refocusing. The 150-500mm is relatively parfocal, requiring only very small adjustments, and the minimum focus is 2.2m across the entire focal length range.

The inclusion of HSM for Pentax on the 150-500mm makes fine AF adjustments as you zoom non-intrusive - they happen invisibly. Subject movement is also tracked much better. The body-drive focus of the 50-500mm means that both zooming adjustments and distance changes produce constant adjustment, which is not smooth like HSM focus.


David
.

Relevant Pages

  • Re: Sigma APO or OS Lens
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