Pentax 16-45mm vs Sigma 18-50mm EX

[plieber]

I've got a contract to take aerial photos of industrial sites. One problem is that some of the sites are rather large (500+ acres) and some need to be shot rather high (3000 - 5000 feet) where haze is a big problem. I need a high quality, versatile lens. I own a Pentax D but will upgrade to the new k10D next month. I am thinking of buying either the Pentax 16-45mm f4 or the Sigma 18-50mm f2.8 EX. Any experience with either lens or suggestions?

I know Pentax is coming out with a 16-50mm f2.8 DA lens next March, but it will be a while before anyone has any experience with this lens.

Thanks Pete

 

[Don Simon]

Sorry, can't give you an answer yet - but I'm consider the exact same thing. Some of the reviews I've googled have suggested that the Pentax is sharp even at F4, while the Sigma needs to be stopped down a bit - I'm guessing also to F4. That would probably make me go for the Pentax; that and the extra 2mm on the wide end - which gives you equivalent of 24mm vs the Sigma's 27mm equivalent. Of course if the Sigma can be had for significantly cheaper I'd definitely consider that too. The extra 5mm on the long end of the Sigma wouldn't do anything for me, since I'd switch to a 50mm prime at that point anyway.

I'm currently waiting for my local shop to make an offer on some of my gear for part exchange, so if I can get my hands on one of these lenses in the next week or so I'll let you know how I get on, send you some test pics etc.

 

[plieber]

Interestingly the Sigma AF 17-70mm f/2.8-4.5 DC macro fared better than the more expensive Sigma AF 18-50mm f/2.8 EX DC Aspherical IF in photozone tests - see
http://www.photozone.de/8Reviews/lenses/sigma_1770_2845/index.htm
&
http://www.photozone.de/8Reviews/lenses/sigma_1850_28/index.htm

Unfortunately the tests were done on a Canon and not a Pentax, but that shouldn't make any relative difference..

Here's another review on the Sigma:
http://www.ephotozine.com/equipment/tests/testdetail.cfm?test_id=342