[jrpower10]

Looking for an ultrawide ff zoom and wondering if anyone has tried the Sigma on a K-1. Is the Pentax IQ significantly better? I'll be using it for landscapes, so stopped down and I'm looking for sharpness across the frame. My previous ff wide lens fell off quite a bit at the edges and the corners stunk.

[UMC]

When it comes to choosing the widest superwideangle zoom for K-Mount, there is no alternative. The Sigma 12-24 DG EX is the widest zoom available for Pentax FF. And don't get mislead, there is a huge difference in field of view between the 15-something zooms and the 12-24, similar to the APS-C 8-16 vs 12-24.

Unfortunately there is a tradeoff: While everything I have seen from the Pentax 15-30 looks excellent, the Sigma 12-24 certainly falls behind, especially wide open and in the corners. Actually, I should rather say, corner sharpness is a disaster, at least my copy shows this problem. See for yourself: Microsoft OneDrive - Access files anywhere. Create docs with free Office Online. Please mind that the generally hazy look of this image is not caused by the lens but by a weather phenomenon.

If you have patience for a few days, I can give you some more hints, as I have just won an auction for another copy last weekend. I hope I'll receive it tomorrow and can do some testing on the weekend.

For now, just one more hint: Sigma had another super-wide angle in their line, the Sigma 15-30mm 1:3.5-4.5 DG EX. This one is slightly faster, but much heavier and bulkier but its image quality is on par with the 12-24. Therefore it may be a cheap but definitely inferior alternative to the Pentax 15-30.

[krazykat]

When it comes to choosing the widest superwideangle zoom for K-Mount, there is no alternative. The Sigma 12-24 DG EX is the widest zoom available for Pentax FF. And don't get mislead, there is a huge difference in field of view between the 15-something zooms and the 12-24, similar to the APS-C 8-16 vs 12-24.

It's actually similar to the APS-C 8-16 vs 10-20 but, yes, even those couple of mm is a big difference.

For now, just one more hint: Sigma had another super-wide angle in their line, the Sigma 15-30mm 1:3.5-4.5 DG EX. This one is slightly faster, but much heavier and bulkier but its image quality is on par with the 12-24. Therefore it may be a cheap but definitely inferior alternative to the Pentax 15-30.

Much bulkier? Yes - 132.5 vs 102.5.
Much heavier? No - 615g vs 600g.


There has been much debate over the image quality of Sigma ultra-wides, both APS-C and FF. Some say the 12-24 is better than the 15-30, some say it's the other way around. (Same for APS-C 10-20 4.5/5.6 vs 3.5/4.5) I've tried my fair share of them and for me it all comes down to the individual copy. But, as you say, they are all definitely inferior to the Pentax 15-30.