[creative69]

My quest was to find an affordable UWA full frame lens for the K-1 which by itself is no mean feat. I stumbled upon an old Sigma lens the Sigma 18-35 f3.5-4.5 which is apparently fairly rare and is obviously from the days of film. Anyway the images attached are taken with a Canon 5dm4 with 17-40 L usm and the Pentax K-1 using the Sigma. Though not a scientific test (whatever that means) I was astonished to see that there was very little if any real difference between the two images. The detail of the sigma appears to be right up there with the canon kit. Furthermore the Sigma showed virtually no distortion compared with the Canon! I've already said elsewhere on this forum how I'd like to use my 645z for interior work but again no UWA option, but the K-1 would be an exciting option especially using pixel shift. Can it be that the K-1 and an old sigma lens that cost me £85 has become my interior setup seeing of the Canon kit which btw cost double the price?
Based upon this result I'm so tempted to buy the Irix 15mm but at the same time I believe Pentax are about to deliver us two new wide angle offerings. One thing is for sure the old Sigma seems to have set the bar surprisingly high so whatever Pentax release better be good.

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[ddamski]

cant comment on the sigma option, but the irix is a good affordable uwa option. Though, probably the first copy of the irix lens could have decentering issues like mine.
I dont think pentax will provide such an uwa lens option with large aperture like the irix, but i could be wrong ofcourse

if you are happy about the results of the sigma why get another lens? maybe first wait to see what pentax will ofer

[creative69]

Yes the Sigma was a surprise at first but it does show its weakness in other areas such as nearer subjects and corner sharpness.
Pentax have already shown UWA on the lens road map. Just need them to hurry up.

[funktionsfrei]

There's an 11mm lens announced by Irix:

Irix - 11 mm

That one would be even wider than Sigmas now-discontinued* 12-24mm zoom lens, which used to be the widest FF offer for Pentax.

*) with Pentax mount. The "mainstream" Canikon market is of course being catered with a new, upgraded version of that lens.