[northcoastgreg]

In reviews on photozone the 10-17mm fared much worse in the CA test than the Samyang 8mm they tested (albeit on different cameras, which could explain the difference)

Photozone tests the thickness of the CA: thicker CAs are "worse." But the real issue is how easy or difficult it is to remove the CAs in post. I can't speak of the Samyang in this regard, but, in Lightroom at least, most of the CA issues with the DA 10-17 can be removed or severely mitigated. In other words, unless you're very uptight about CA, I wouldn't regard it as an important issue.

Another thing about photozone reviews: they tend to concentrate only on those aspects of a lens that can be measured. But there's far more to a lens than what can be measured. The DA 10-17 was supposedly designed by Jun Hirakawa, who is on record as stating he doesn't care about measurements; what's important, rather, is the uniqueness and beauty and piquancy of the final image produced by the lens. The Samyang may produce narrower CA and a bit more resolution than the DA 10-17, but does it produce better images? Not from what I've seen. The Samyang doesn't come close to producing the rich, vibrant colors or the excellent microcontrast of the DA 10-17. The Samyang also, from what I've heard, doesn't have the flare control of the Pentax lens -- but that's another feature photozone fails to test for.

[loco]

The Samyang is less than half the price. I love the photos I've seen from the Pentax 10-17, but I have not seen it being twice as good.

If the OP wants the best, price no object, they may go for the Pentax. But for me, not knowing how much I'd use a fisheye and not having much money to spend, the Samyang was the perfect choice. And if you get one of the other branded Samyangs, such as Bell and Howell, you can get it for even less. Mine was $239.

I figured if I really loved using the fisheye and wanted something even better in the future, I could sell the Samyang and get a better lens. So far, even though I love the fisheye, I see no need to "upgrade."

[jezza323]

thanks for the inputs all

as always cost is of some concern, as is flare and size/weight. on all those basis it seems the Pentax is probably the best lens for me, even though it is a zoom and will unlikely get zoomed much

i guess now i just need to convince the wife, and find myself a copy that is reasonably priced

[pop4]

Am I crazy for wanting a fisheye given that I already have the Sigma 10-20mm (I don't think so)?

As someone with both a Sigma 10-20/3.5 and Pentax 10-17/13.5-4.5 fisheye, I think no, you're not crazy. Even though the focal lengths overlap, they are two different lenses that serve different purposes.

[interested_observer]

As someone with both a Sigma 10-20/3.5 and Pentax 10-17/13.5-4.5 fisheye, I think no, you're not crazy. Even though the focal lengths overlap, they are two different lenses that serve different purposes.

You can not compare focal lengths of fisheye and rectilinear lenses. The only way to compare them is through their respective Angle of View (AoV).

• The Sigma 10-20/3.5 has an AOV ranging from 100 degrees at 10mm to 61 degrees at 20mm

• The Pentax 10-17/13.5-4.5 fisheye has an AOV ranging from 180 degrees at 10mm to 100 degrees at 17mm

So these two lenses complement each other very well in terms of coverage of scene.