[VoiceOfReason]

I do have my 18-35 under warranty right now and the same for my 12-24...

[goldenarrow]

Yeah, under warranty it's free, and if I recall right they even pay the return shipping. But outside of warranty I think it's about $120 and you're responsible for shipping, so it's definitely something that ads value to buying a Sigma.

Sure, Pentax has added micro AF adjustment to their bodies, but the tuning is rather coarse since it only has a certain number of adjustment points you can choose from, and it only extends a certain amount in either direction, so in some cases it may not quite get there. With a modern high-megapixel sensor and a very thin DOF from a fast telephoto, it's nice to be certain that you have perfect calibration, and are not leaving any resolution on the table.

Every time I've had service done, whether just calibration or an actual repair, I've sent my items to their NY headquarters. Turn around time has typically been a day or two every time.

thanks for the practical info. I have recently consolidated lenses and ended up with two used sigma zooms in exc+ condition. I like them a lot. Pentax alternatives are too expensive for me at this time for the perceived increase in performance. The 70-200 sometimes front focuses slightly. I may send it to NY. But do I also have to send my new K3 with it???

This Pentax 24-70 might be more interesting than Sigma offerings. I am concerned about the "cat's eye" bokeh based on photozone tests of the Tamron version. I am purposely being picky since I am happy with only two zooms (sigma) and three primes (pentax). I also figure that if I just want snapshots, I will get a smaller superzoom camera instead of a do-everything zoom. we'll see how lens tech advances confirm or confuse me.

[Class A]

So you're suggesting Pentax lenses should only be chosen as an alternative to sigma lenses?

Please get your quotes straight. The sentence you quoted was by Edgar_in_Indy, not by me.

[Class A]

Class A is a big proponent of Sigma glass and even in cases like the 18-35 f1.8 auto focus issue, is unwilling to believe that there truly is a problem.

What if I'm right in my refusal to believe that there truly is a problem?

FYI, I never said that there aren't any copies that have problems. I do not doubt that some people experienced issues, but

1. the extent of the issue seems nowhere near the magnitude of the SDM tragedy.
2. a number of people with issues did not give Sigma a chance to rectify the problem. Digitales, for instance, chose to have his lens serviced somewhere else. I appreciate that he had problems with CRK, but AFAIC, he should have either stuck to his guns with CRK, or should stop blaming the product / company.
3. I pointed to many post of people who had absolutely no AF issues with the 18-35/2.8. Yet, such posts are just ignored by the typical Sigma bashers as they don't fit their worldview. The posters contributing to the "The Sigma 18-35 f/1.8 Art club" thread must have a terrible time getting their shots done -- according to the Sigma basher -- yet we don't hear a peep from them regarding AF issues.

I do not exclude the possibility that there might be a problem with some copies that Sigma could address one way or another, but given the many happy users of the lens I do not think that a general "do not touch this" lens warning is justified at all.

As for my experience with Sigma lenses, I have five and they are all great performers with no issues whatsoever. My experience with Simga service (one exchange and on AF adjustment) has been great. I'm not sure how many more Sigma lenses I would need to be qualified to voice an opinion about Sigma glass.

On the subject of "Sigma being cheap". On three of my Sigma lenses that I bought new, I got a six year warranty, a clear statement that Sigma is standing behind the quality of their products.

[Class A]

The 70-200 sometimes front focuses slightly. I may send it to NY. But do I also have to send my new K3 with it???

Yes, you should. Achieving focus is an interplay between the camera and the lens. You cannot calibrate a lens so that it will work perfectly on all bodies. As a matter of fact, in many cases the camera is to blame when focus is not achieved and according to a service centre technician I spoke to, often the lenses that are sent in are fine, but the cameras need the adjustment.

[Digitalis]

Please get your quotes straight. The sentence you quoted was by Edgar_in_Indy, not by me.

sorry for the forum quoting blooper. For some reason the quick quote tool thought you said that.

As a matter of fact, in many cases the camera is to blame when focus is not achieved and according to a service centre technician I spoke to, often the lenses that are sent in are fine, but the cameras need the adjustment.

This comment gives rise to an opposing point of view: If the camera manufactures lenses operate with no or minimal AF adjustment needed, and a third party lens which needs hundreds of dollars worth of optical adjustments and hours worth of AF calibrations to only get it work with only barely acceptable accuracy, one has to wonder the accuracy of such a statement. I wouldn't rely on the statement of one service technician to cover all scenarios. Yes, there is a chance of camera bodies being the culprit of AF accuracy issues*, however the lenses can also be at fault. I'm prepared to admit there is a bell curve distribution here regarding AF accuracy and the the 18-35mm f/1.8 lens, and I happened to be on the wrong side of the middle: however you can't say i'm the only one.

* For instance the D800/810/D4 asymmetrical AF issue, where in that particular model of DSLR nearly all cameras had inaccurate AF sensors on the left half of the AF module.This was later corrected by Nikon who gave their service centers the ability to correct the AF issue for users who sent in their cameras to get their AF module software re-calibrated.

What if I'm right in my refusal to believe that there truly is a problem?

Sigma fanboys always refuse to believe that Sigma still has an unchanged quality control issue.

I had several Sigma lenses and none of them worked as advertised. There is only the cheapness to work for Sigma in general if you like to gamble with the risk of it.

The continuous problems with Sigma lenses are also caused by poor design decisions.
The size quality of the new art lenses is poor as everyone knows.
The weight quality of the lenses is poor as well.
The cheap plastic feel is not good either.
The repeated quality problems of the Sigma 18-35 are not only quality control but probably a design screw-up where they chose a wrong part tolerance.
The really bad focus shift on the 50mm non-art also is a Sigma design problem.

And why do you think Sigma has to offer multiple years of warranty where Canon does not? Simply because nobody in the right mind would want to buy this otherwise.

Which other manufacturer has so poor quality control as to sell repair kits (USB docks) for their lenses?

And no: The most stupid thing you can do is to send a camera body to calibrate a lens. Both lenses and body have to be calibrate to a neutral setting. Else you will have to re-calibrate all lenses for a new body.

A few hours later I gave up:
This lens mis-focuses in a way I have never ever experienced before, not even with the most crappy third party lens from 20 years ago!
The only way to describe it is "Focus Lottery"!
No reproducable front or back focus ... the focus point is all over the place. Essentially random.
Is this maybe Sigma's idea of an "art lens"?

Amazon.com: Sonja's review of Sigma 18-35mm F/1.8 DC HSM Lens for Pentax...

this lens had trouble focusing if used with Phase Detection AF (Canon 70D), almost 95% of the shots are out of focus, becomes worse if you use the center focus point with wide open aperture. checking online confirmed that it is a common issue , and a firmware update did not help at all, I am returning my lens.

Amazon.com: Outsider's review of Sigma 210101 18-35mm F1.8 DC HSM Lens for ...

Sigma 35mm 1.4 beware of focus issues close to infinity
Sigma 35mm 1.4 beware of focus issues close to infinity: Third Party Lens Talk Forum: Digital Photography Review

Sigma 18-35 – focus issues
Sigma 18-35 ? focus issues: Third Party Lens Talk Forum: Digital Photography Review


focus issues with Sigma 18 - 35mm f1.8 zoom
focus issues with Sigma 18 - 35mm f1.8 zoom: Nikon SLR Lens Talk Forum: Digital Photography Review

If anyone does not wish to buy an SDM lens older than 5 years he certainly shouldn't buy a new Sigma 18-35 "art" lens. You can find some good copies out there, but you definitely should be aware of the risk with Sigma.

I do think even advocating this lens without clear quality warning is just reckless. That is not bashing that is being fair and honest to other people and their money.

Digitalis is quite right in his comments.

[noelpolar]

But you forgot the biggest advantage of the Sigma 85mm...its huge size will impress your friends and confuse your enemies!

Now days.... my Sigma 70-200/2.8 is considered by many as a super size lens........then (for that special person) I bring out the DFA 150-450........just when you thought it was all figured out.

[Digitalis]

At the risk of further de-railing this thread...

Which other manufacturer has so poor quality control as to sell repair kits (USB docks) for their lenses?

You're going a bit far here, the AF calibration dock doesn't cure all AF issues, nor does it compensate for poor optical alignment.



The maddening part about the lens dock is that is offers no adjustment between infinity and 2m, which is where 90% of the AF issues occur with the 18-35mm f/1.8

The most stupid thing you can do is to send a camera body to calibrate a lens. Both lenses and body have to be calibrate to a neutral setting. Else you will have to re-calibrate all lenses for a new body.

This is actually a really good point. I have a considerable amount of Pentax lenses, sending my camera in to get it adjusted for the AF inaccuracies of one lens - and take the risk of throwing out all the calibrations for all the other lenses I own, is a risk I cannot take.

And why do you think Sigma has to offer multiple years of warranty where Canon does not? Simply because nobody in the right mind would want to buy this otherwise.

That isn't exactly fair, just because they are offering an extended warranty on their product doesn't imply the manufacturer expects it to fail within that time frame, If sigma really wanted to be Evil about it they would offer a shorter warranty. Canon offer extended warranties and I have seen more Canon cameras and lenses fail than Sigma. Though to be completely honest, Sigma isn't far behind on Canon when it comes to failure rates.

[pinholecam]

Since its already raining on the parade and multiple occurrences of rain too.

Let me add my Sigma woes.

1. Sigma 10-20 - severe focus problems that could not be compensated on my K7. Sent it into Sigma service center (a hell of a travel time and open only during office hours which meant I wasted my leave to settle it). When 3x in total.
Had to leave my 1 week old K7 there too for the tech to fine tune (with loads of shutter count added as a result - what a heart pain)
In the end tech only said its calibrated 'to factory tolerances' - thats after 3 weeks - did not sound very convincing.
Still add the odd focus here and there with the lens after that.

2. Sigma 50/1.4 - thought it a good idea to buy one in HK where its considerably cheaper. Popped into 2 stores, both had 1 lens each in PK mount. Both had FF/BF issues (pretty common issue with early versions of this lens )

3. Sigma 30/1.4 - same as the 50/1.4

4. Sigma 28-200 - oil separation from the grease after 3-4yrs of use.

Not all that rosy in Sigma land too.

[Catscradle]

When can we expect PF to receive a copy of this lens and post a review. Just curious.

[Edgar_in_Indy]

This is actually a really good point. I have a considerable amount of Pentax lenses, sending my camera in to get it adjusted for the AF inaccuracies of one lens - and take the risk of throwing out all the calibrations for all the other lenses I own, is a risk I cannot take.

I'm pretty sure that Sigma calibrates the lens to the body...not the body to the lens. I don't know if you meant to imply that it is the other way around, but that's what it sounded like to me.

The other guy was saying that ideally, lenses and camera bodies would be calibrated to the neutral point. That sounds great in theory, but I'm not sure how I would go about actually getting that done. I would not have confidence that I would be able to get a Pentax service center to actually do such a thing, and do it right.

Has anybody here actually had that done at a Pentax service center? I think they would be likely to say that the body is already within acceptable range, but if somebody has first-hand experience with this, I would love to hear it.

Yes, there is a chance of camera bodies being the culprit of AF accuracy issues, however the lenses can also be at fault.

But you made a good point that calibration is not all in the lens. Manufacturing tolerances also apply to the camera bodies. I witnessed this first hand when I upgraded from my K-x to my K-30...calibration was drastically different. So in my experience, Pentax is not better than lens manufacturers in this regard. Which is why I found it useful to have my lenses calibrated to my specific body.



In fact, this whole calibration thing is something I hate about DSLR's, and is one of the reasons I have not upgraded to the K-30, and have been looking hard at mirrorless.

I sold a Sigma 100-300mm f4 to someone on the forum last year, and on my K-30 it worked beautifully with perfect focus. But the buyer, who had a K-5, claimed that it was too far out of calibration to correct on his body, and forced a return through PayPal, even though I had discussed possible camera body calibration issues with him before the sale. I then resold it on eBay as "for parts or repair" at a significant discount since I didn't want to deal with a second return, and the second buyer used it on his K-3 without any issues and was delighted with it and left gushing feedback. So yeah, I'm pretty sore on the subject in general, and it seems to me that Pentax bodies are a moving target in terms of calibration.

I recently bought a Panasonic GX7 to test the waters before committing to the GX8, and so far I've been enjoying it thoroughly. I've picked up the Panasonic 20mm 1.7 and Olympus 75mm 1.8, and they've been great, with no need to worry about calibration since focusing is performed on the image sensor itself. To me, this is the way of the future, and I will be happy to never have to mess with calibration again.



BTW, it seems like I remember reading something about how one of the big manufacturers (can't remember if it was Nikon or Canon) has made it so that when using their newer lenses on their newer DSLR bodies, there is some kind of feedback loop such that takes place so that the camera can detect and correct for calibration discrepancies between the lens and body, and you end up with perfectly focused images. Does this sound familiar to anyone else? It seems like it was an article written by lensrentals.com. It would be nice if Pentax could incorporate a similar system in their AF.

[Zygonyx]

BTW, it seems like I remember reading something about how one of the big manufacturers (can't remember if it was Nikon or Canon) has made it so that when using their newer lenses on their newer DSLR bodies, there is some kind of feedback loop such that takes place so that the camera can detect and correct for calibration discrepancies between the lens and body, and you end up with perfectly focused images. Does this sound familiar to anyone else? It seems like it was an article written by lensrentals.com. It would be nice if Pentax could incorporate a similar system in their AF.

I read the contrary elsewhere : Nikon would somehow "scramble the signal" of third-part originating lenses, Sigma in particular.

[Edgar_in_Indy]

I read the contrary elsewhere : Nikon would somehow "scramble the signal" of third-part originating lenses, Sigma in particular.

You misread what I wrote. I was talking about "their" lenses on "their" bodies. So it was a benefit to using Canon lenses on Canon bodies, or Nikon lenses on Nikon bodies. Can't remember which. But they basically had special circuitry in their newer lenses to correct calibration on the fly by providing feedback to the camera body. This is obviously a feature which would require collaboration between the lens and the camera body, which is why it was a feature restricted to the latest first-party lenses. It also indicates that the DSLR maker was aware of the problem of calibration issues, even with first party lenses, so they took steps to compensate for it.

But about what you said, if someone was intentionally making it so that 3rd party lenses would not work, that would be disappointing. It seems like there have been successful lawsuits in other industries in regards to OEM's taking steps to block use of 3rd party accessories. Maybe Microsoft got smacked for locking competitors out of their platform? But then again, you have the inkjet printer makers who have tried to make it impossible to use 3rd party consumables. The legality of such practices probably varies from case to case and industry to industry.

But in any case, I don't think Pentax would be well advised to make it hard on Sigma and Tamron, since it opens up the universe of lenses and makes their system more viable for more people. With Canon and Nikon, on the other hand, most people could get along quite well without any 3rd party lens support.

[Rondec]

You misread what I wrote. I was talking about "their" lenses on "their" bodies. So it was a benefit to using Canon lenses on Canon bodies, or Nikon lenses on Nikon bodies. Can't remember which. But they basically had special circuitry in their newer lenses to correct calibration on the fly by providing feedback to the camera body. This is obviously a feature which would require collaboration between the lens and the camera body, which is why it was a feature restricted to the latest first-party lenses. It also indicates that the DSLR maker was aware of the problem of calibration issues, even with first party lenses, so they took steps to compensate for it.

But about what you said, if someone was intentionally making it so that 3rd party lenses would not work, that would be disappointing. It seems like there have been successful lawsuits in other industries in regards to OEM's taking steps to block use of 3rd party accessories. Maybe Microsoft got smacked for locking competitors out of their platform? But then again, you have the inkjet printer makers who have tried to make it impossible to use 3rd party consumables. The legality of such practices probably varies from case to case and industry to industry.

But in any case, I don't think Pentax would be well advised to make it hard on Sigma and Tamron, since it opens up the universe of lenses and makes their system more viable for more people. With Canon and Nikon, on the other hand, most people could get along quite well without any 3rd party lens support.

I think brands just change certain things in their auto focus module. Unfortunately it can mean that third party lenses cease to work appropriately on new gen cameras. I would say it is a side effect of Sigma's reverse engineering rather than a specific goal of Canon or Nikon to make the lenses stop working. Sigma often comes out with updates in these situations, but you usually have to send your lenses in to get them fixed (I remember some issue with certain Sigma lenses not working in live view on Pentax cameras, not the end of the world, but it did require the lenses to be sent in to fix it).