[ElJamoquio]

I still like the 15mm and the 35mm. I like the 100mm too but I can't remember if that's a Tokina lens or a Pentax lens, and I also can't remember when the optics were designed. The DA*300mm is also very nice. Not sure when the optics were designed. The 70 is pretty good too.

[Digitalis]

I returned mine because I got good shots in total shade, but in sunlight it horribly overexposed the scene

Even when I was using matrix metering with this lens I didn't have any problems like this. And Sometimes I get lazy and use TaV mode.

[DennisH]

Even when I was using matrix metering with this lens I didn't have any problems like this. And Sometimes I get lazy and use TaV mode.

I'm certainly not discounting user error, and it's not the only reason I returned it, but I found it frustrating to use.

[EarlVonTapia]

This lens is fantastic! Really well made, no wobble, squeeks, or etc. It handles very well and has a reassuring feel to it. I like the finish of the lens and also the way how it looks on my K-5.
Optically it is exactly as advertised. Great at f1.8 throughout the range and fantastic once stopped down to f2.5.

Attached are a few pictures taken with it (plus the obligatory cat picture)

Flare test

For the flare test, can you (or another owner of the Sigma 18-35) test the flare at different apertures? Flare presents differently at different apertures. I'm curious to see the flare resistance of the lens at f8 and beyond, since those are probably going to be the most common apertures when using it for landscape scenes with the sun in the frame. Such a test should also reveal the quality of the starburst it can produce.

I've attached a picture of a flare test I did with my Tamron 17-50. The top picture is at f2.8, the middle at f8, and the bottom at f16. There is no flare at f2.8, but at f16 it's definitely present.

The picture of the cat is amazing coming from a zoom lens. I'll be eagerly reading up reports from real-world use of the lens as they pop up.

Attached Images

 

[Digitalis]

this is hardly the first lens to have copies that suffer from de-centering.

Do you think this is acceptable considering how sigma has made much noise about their A1 MTF testing for each lens they produce to quote sigma:

"The lenses in our new lines will all be checked using this new system before they are shipped.Thanks to our new sensors, with their extremely high resolution, you can expect our high-performance lenses to be better than ever.

At the heart of the A1 measurement system is the same Merrill Generation 46 Megapixel Foveon sensor in the Sigma SD1 Merrill, and the Merrill Generation DP cameras. The incredible resolution of this sensor makes it perfectly suited to this advanced scientific purpose. The lenses to be measured are hooked up to the image capture device, and the special charts are captured and analyzed using new, proprietary algorithms designed to work in conjunction with the high-resolution sensor.

This level of detail analysis is critical for creating lenses capable of meeting the demands of the most detailed image sensors in cameras such as the Sigma SD1 Merrill and the Nikon D800.

As you know, the 46-megapixel Merrill Generation Foveon sensor is APS-C format, capable of both super high resolution and super micro detail. So, in order to test the lenses edge to edge, and corner to corner, to cover the entire 35mm image circle, the first test image is made at the center of the frame, and then the sensor is moved to a corner of the image circle, and repeated for each remaining corner.

The data is analyzed and the tester then determines if the lens has met the quality control standards.
And every new lens designed in the Contemporary, Art, and Sports lines will be tested with the A1 device–meaning 100% of the lenses built will be analyzed and approved before leaving the factory in Aizu."

(bold text added for emphasis)

So my question is: how in hell did my lens show up defective on my K5IIs when they have a X3 sensor with similar resolution testing these lenses? and what do they do with the lens testing data they have collected after it is captured?

[rawr]

So my question is: how in hell did my lens show up defective on my K5IIs

No matter how good the lens may be when it leaves the factory, if the Fedex guy drops or kicks the parcel somewhere along the way between Sigma, the regional Sigma distributor (CRK), the store you bought it from, and the customer, then you may also expect problems. So it may not directly be a Sigma QC issue.

I've seen how couriers (and baggage handlers) deal with small parcels sometimes. It's not always pretty. If Sigma were really serious about QC, they would include a G-force sensor in the box when they pack the lens.

[Digitalis]

no matter how good the lens may be when it leaves the factory, if the Fedex guy drops or kicks the parcel somewhere along the way between Sigma, the regional Sigma distributor (CRK), the store you bought it from, and the customer, then you may also expect problems. So it may not directly be a Sigma QC issue. I've seen how couriers (and baggage handlers) deal with small parcels sometimes. It's not always pretty.

That is certainly possible, I did notice the lens case the 18-35mm f/1.8 is exactly the same as the one my Sigma 8-16mm f/4.5-5.6 EX DC came in, and that doesn't offer much in the way of padding. Then there is the point of my second question: if they have the lens test data from the factory and somewhere between the lens being packaged and arriving at the store, publishing ( using the lens serial number as an access code) it would give the end user a frame of reference of what the performance from the lens is supposed to be. And it would help pinpoint whether the lens was damaged in transit.

[Class A]

I returned mine because I got good shots in total shade, but in sunlight it horribly overexposed the scene.

The camera determines exposure, not the lens. Unless the aperture blades are stuck, a lens does not negatively affect exposure in any significant way.

Same goes for focus hunting; it is typically a camera issue, not the fault of a lens.

Regarding bad bokeh: I'd like to see one lens that you cannot make look bad somehow.

So it may not directly be a Sigma QC issue.

Exactly.

And even if now and then a copy escapes that isn't quite up to snuff it would be completely normal for a lens in this price bracket. No need whatsoever to call Sigma's QC "lacklustre". I could go on about a multitude of Pentax QC problems (with respect to a number of lens models and also camera issues) which are widely known so I really don't know why some feel the need to point at Sigma. If Sigma's QC is "lacklustre" then Pentax's QC is what?

Anyone with eyes in their head can tell from image samples that the 18-35/1.8 is an amazing lens and I hope that future lenses from Pentax will come close in quality. I have very little hope that future Pentax lenses will be anywhere near as attractively priced, but I'd be more than happy to be proven wrong.

[Digitalis]

Regarding bad bokeh: I'd like to see one lens that you cannot make look bad somehow.

I've seen bad bokeh before but I can't say I have ever seen anything like this before that didn't come from a mirror lens :


un-sharpened 100% crop - I was testing this lens for purple fringing issues, turns out I uncovered something that is categorically worse.

I know bad bokeh when I see it...but this, I don't really what to make of it...it isn't good it, isn't bad...it is ugly.. it's the visual equivalent to Thioacetone.. I really do hope the frog egg bokeh is just a symptom of the centering defects present in my copy of the lens, because it crops up quite a bit in the images I have.

[thibs]

And even if now and then a copy escapes that isn't quite up to snuff it would be completely normal for a lens in this price bracket. No need whatsoever to call Sigma's QC "lacklustre". I could go on about a multitude of Pentax QC problems (with respect to a number of lens models and also camera issues) which are widely known so I really don't know why some feel the need to point at Sigma. If Sigma's QC is "lacklustre" then Pentax's QC is what?

Anyone with eyes in their head can tell from image samples that the 18-35/1.8 is an amazing lens and I hope that future lenses from Pentax will come close in quality. I have very little hope that future Pentax lenses will be anywhere near as attractively priced, but I'd be more than happy to be proven wrong.

Agreed about your QC point in general but you have to admit that once a brand makes such vocal promises about something, it has to be able to sustain it, otherwise they are fools.
Better shut once mouth than make false advertisement. And this is quite easy to demonstrate legally if needed. I'd be Sigma, I'd be cautious now. VERY.

[Class A]

Better shut once mouth than make false advertisement.

Sure, but we really don't know whether Sigma did anything close to false advertising.

Lenses can take damage during transport, or pass QC and develop a problem later on, because something becomes loose (e.g., there are copies of FA Ltds, that did not have the thread lock on the front group screws applied properly so the latter become loose over time and suddenly you are holding multiple pieces in your hand).

I don't see why Sigma needs to be "cautious". They just have to do their QC, as announced. Problems happen; making certain QC announcements cannot mean that all lenses will stay perfect till all eternity.

People should realise that Sigma still produces in Japan (as opposed to Vietnam, say) and is a family-owned business. They produce some lenses that beat genuine equipment in terms of optical performance, reliability (e.g., compared to SDM), and price. Their warranties are also typically much better than what you get elsewhere. I bought Sigma lenses with a six (6) year warranty (not paying anything extra). The current standard in Germany is three years.

All this is pretty amazing. I consider myself very lucky that Sigma still produces lenses with a K-mount. Many other lens manufacturers abandoned Pentax quite a while ago.

[Edgar_in_Indy]

Do you think this is acceptable considering how sigma has made much noise about their A1 MTF testing for each lens they produce to quote

I did not say it was acceptable. My point was that every lens maker delivers lenses with de-centering. I can't recall the times I have read about complaints of de-centering in various first-party lenses, including Pentax. And supposedly first-party lenses are the standard of quality.

But I do see what you mean about the stated testing process. They certainly have set a high standard for themselves, so hopefully the de-centering you experienced is not typical.

[dadipentak]

I've lost the hood. It must have come off silently while I was wandering about yesterday with the camera on the BlackRapid strap. Just a warning to those who buy this lens: the hood has a tendency to pop off.

[Edgar_in_Indy]

I've lost the hood. It must have come off silently while I was wandering about yesterday with the camera on the BlackRapid strap. Just a warning to those who buy this lens: the hood has a tendency to pop off.

That SUCKS. Sigma usually sells various replacement hoods separately, but if you call them and make a case that you lost the hood because it was too loose, maybe they'll help you out.

I've never had a problem with loose hoods on any of my Sigma's, so I don't think it's normal. The only lens I can think of that had a loose hood was my Pentax 18-55mm kit lens.

[Sorver]

I find it funny, and kind of sad, that this is the fastest wide angle AF lens available for Pentax, and it's a zoom. Pentax, where are my fast, wide angle (preferably WR) primes?

I have to say I am with you on that one guess that is one for the wish list 😀. I guess there really is a limited market for them.