[Edgar_in_Indy]

still a lot of hassle if one can just get a good copy

If the lens is in warranty, then to me it seems like less hassle than going through the return process, without any assurance that the next lens will be a better match for your camera.

[interested_observer]

I have had the 8-16 for a bit over a day. Shot about 5 set of images, morning and evening light. Yes, I was initially disappointed with the sharpness. I expected it to be less sharp than the 12-24 but more sharp than the 10-17. What exactly that means, I still really can not say. I can say that its closer to the 10-17 at 10 then anything else. But I have found that it likes to focus lock way beyond infinity. That just skews the images and puts an additional unknown factor on the results. I have applied a +10 fine AF adjustment this morning and that has helped. That said, I don't know what an optimum result for this lens is - yet.

The more I look at the shots and understand how the lens works with the sensor, I am starting to develop an approach. This lens does take a lot of work (to understand), even if you have done a lot with a reasonable number of WA/UWA lenses. Still mulling things over, but the 8-16 lens is only for general overview scenes (my opinion for what its worth), nothing where good IQ and "standard" sharpness is going to need to be applied. For that, I need to shoot and stitch the 12-24, I think to really get what I think I want. The 8-16 has really wonderful color rendering, much closer to my 10-17. That is the one area that the 8-16 substantially beats the 12-24 right out of the box. You are acquiring this lens for its ability to take in a really wide field of view (essentially 8mm), but in doing that you are making a sub conscious trade in terms of some level of sharpness. When I say "standard" sharpness, what does that mean - I don't have a clue. The reason for this, is that this lens is so wide that there is not a uniform or linear merit to apply. For each 1 mm of width you are adding beyond what you are use to using, the field of view (or angle of view) is increased an ever larger amount. This throws your sense of proportion off - plus the beyond infinity focusing ability just adds confusion to this.

I never thought I would say this but perhaps this is where a 24MP sensor will really shine. The 8-16 essentially quickly balloons up the area that is crammed into each pixel, especially at the 8mm end. The 24MP sensor would essentially skinny this area down to approximately match that of the 12-24. So in essence, the 8-16 would probably do a lot better on a higher resolution sensor. Again just my opinion, especially since I do not have anything beyond the K5.

The 8-16's auto focuses well beyond infinity, was something that I really did not expect, and it does throw you for a loop. That coupled with the sharpness some where between the 12-24 at 12 and the 10-17 at 10, and then you mix in the fish eye vs rectilinear difference, you no longer have a really well defined reference point in which to compare and evaluate what you are observing. I still really need to figure out if +10 is the best AF fine adjustment or if some other value would be better.

Out of about 30 - 40 shots, there are a couple that have pretty good sharpness, now that I have some background understanding as to what is involved with all of this. That brings up lack of consistency. OK, shooting some in the morning with the sun coming up and in the evening with the sun going down, isn't an exhaustive test. Is it fair - to a degree - for my situation - yes, since that is how I plan to use this lens. Where I am going here, is that say you take 10 shots. If you succeed on AF lockon early, then you can have pretty good success staying on lock with out going beyond infinity. If you don't achieve that early lockon in the set, then you need to look at lens' focus distance indicator and see if you are beyond infinity - if so, manually focus back to infinity and try again. But that is just my current take of a sample of 1 lens. Is this a bad copy. I am now thinking probably not, but I think that there is sufficient tolerances involved here that you have to have a understanding of what is going on. This is an extreme lens for a rectilinear. You have to take that in to consideration. Its also a lens (that for me) with the over focus condition, presents a different situation in terms of handling characteristics.

I am starting to rethink the lenses as they apply to each of the locations I wanted to shoot. This lens is going to take a lot of work to really understand its strengths and weaknesses and to apply them correctly to the situations at hand. Would sending the body and lens to Sigma for calibration be the answer? Possibly, but I have a week and a half and I don't want to take a chance of getting everything back late and missing the window of opportunity. So, I will take this, use what I have, gain some more working experience with this, increase my understanding in terms of how to apply what I have, and run with it.

Been giving this a bit of though in terms of determining the best AF fine adjustment value. Going to take my DA 12-24 that I Really like (did I say I really like it), and at 12 mm shoot the large octillio (a big bush) mid day, lots of light on a tripod a couple feet away. Then going to shoot the 8-16 at 12, and find the best AF fine adjustment value to get the best sharpness and focus lock on. The comparison of the two lenses at 12 mm should help me keep a good frame of reference for comparison. Then see how the 8-16 performs at 8 with this AF fine adjustment value - and call it good.

[Edgar_in_Indy]

Would sending the body and lens to Sigma for calibration be the answer? Possibly, but I have a week and a half and I don't want to take a chance of getting everything back late and missing the window of opportunity.

You're in Arizona? In addition to their headquarters in NY, Sigma lists a location in Arizona as a service center:

C.R.I.S.
250 N. 54th Street
Chandler, AZ 85226

If that is close to you, perhaps you could actually take your lens there and have the work much quicker. I sent my camera/lenses to NY each time, so I don't have any experience with the Arizona location.

[normhead]

It's hard to comprehend a lens coming new, so far out of adjustment. Where I live this lens is only available for Pentax by special order. So that's really hard to play dealer Ping Pong. Maybe I'll move it back down the list to the ... "if I have money and time to fool around" position. It's not actually a spot on my list but maybe I'll make one. It probably comes right after the "I probably won't use this but if I ever need it , it would be nice to have it handy." position. That puts it well behind the 15 Ltd. after moving ahead briefly.

[interested_observer]

You're in Arizona? In addition to their headquarters in NY, Sigma lists a location in Arizona as a service center:

Edgar, That question was starting to bounce around my empty mind as I was struggling to wake up this morning while the dogs were wining to go out. Yup, I know exactly where it is. That, might just solve this dilemma. I'll give them a call from work this morning and see what can be arranged.

It's hard to comprehend a lens coming new, so far out of adjustment. Where I live this lens is only available for Pentax by special order. So that's really hard to play dealer Ping Pong. Maybe I'll move it back down the list to the ... "if I have money and time to fool around" position. It's not actually a spot on my list but maybe I'll make one. It probably comes right after the "I probably won't use this but if I ever need it , it would be nice to have it handy." position. That puts it well behind the 15 Ltd. after moving ahead briefly.

Morning Norm, Its ability to focus way beyond infinity, along with the need for a fine focus adjustment, all coupled with the lens being so wide that the area being represented by each pixel gets really very fat, along with at the 8mm end each additional mm just keeps getting wider, presents the users like me as to how to characterize this lens. Its not bad - just different. I do have a few applications for it. There is this very large hole in the ground a bit north of here, that is of a size that should befit its abilities. They have the audacity of calling it the Grand Canyon. Actually, with the colors up there, I would think they work very well with this lens' ability to render colors so richly. The 8mm end of the lens is the widest available, and folks go for that. I am coming to the conclusion that the best aspect of the lens is its ability to render colors so richly and is not a fisheye.

The difference between 15mm and 8mm is like comparing 2 dissimilar lenses. Its only 7mm (almost 100% of the lens' focal range), but in this case the 15 Ltd might as well be a short telephoto.

[Edgar_in_Indy]

You make some good points about how the autofocus works with the extreme 8mm wide angle. There are no other lenses with such a wide angle to compare autofocus performance with, and I would bet that the camera makers didn't spend a lot of time testing their autofocus system with such an extreme angle.

[philbaum]

Interested Observer,
After reading your continued trials with the 8-16, you may very well have a bad copy. Even though my Sigma 10-20 wouldn't alway AF at 10mm, i was always able to manually focus it and get sharp images.

Perhaps you are going overboard to rationalize the lack of sharpness at 8mm. Keep it if you want, but I'm getting suspicious over that lens - shouldn't be that much trouble.

best wishes, phil

[interested_observer]

So here is the rest of the story....

As I was walking out of the house this morning on my way to work, I grabbed my camera with the lens, thinking if I had a couple of minutes I would call C.R.I.S and see what may be able to be done. I did have a couple of minutes and called. They suggested that if I could bring in the camera and lens they could have their Sigma tech take a look at it..... So, I just hopped in the truck and motored on down there. The prognosis is that I had dialed in +10 units of AF fine focus adjustment - which was not quite enough. It is going to need at least another +35 units (around +45 total) with an alignment. No parts necessary (thankfully, since that would take at least 4 weeks). If I would leave the camera body, they would calibrate the lens to the body....

Sweet!!!

It should be ready for pickup on Friday afternoon. What can I say - other than Thank you Edgar for making the suggestion - got me thinking that I should actually try it. When I get it back, I'll post some images. I don't know what to expect, but this can be in some respects a reference.

... and Thank You C.R.I.S.

!!!!!!

[Edgar_in_Indy]

I also found that with my Sigma 50-150mm on my new K-30, the 10 units of adjustment wasn't enough to completely compensate, so that was when I decided to just send all of my Sigma lenses to them at once and have them calibrated properly. The funny thing is, the 50-150mm was PERFECT on my K-x right out of the box. And I had even sent the 50-150mm with my K-x when I sent the 30mm f1.4 in for calibration, and Sigma had also confirmed that the 50-150mm did not need any adjustment. So I don't know whether the big calibration problem was in the lens or the K-30, or if it was actually the K-x that was out of spec.

And my Tamron 28-75mm required an adjustment of 10 to focus perfectly. (And that's another lens that focused perfectly on my K-x wihout any adjustment!) So based on my experience and what the C.R.I.S. tech told you, there are many situations where the +/- 10 units of adjustment will not be enough.

I wonder if the amount of AF fine adjustment provided to the user is just a matter of firmware, or if there is some mechanical limitation in the camera. I wouldn't think so, since my understanding is that the phase detect autofocus is based on the output of a sensor, so it seems like they could program as much AF adjustment capablity in as they want to.

[Edgar_in_Indy]

The prognosis is that I had dialed in +10 units of AF fine focus adjustment - which was not quite enough. It is going to need at least another +35 units (around +45 total) with an alignment. No parts necessary

BTW, did you remember to zero out your AF adjustments in the camera body before dropping it off? I wiped out all of my adjustments before sending it to Sigma so that I would have some room for future adjustments in either direction if I ever felt a need to tweak it. If you forgot to do that, it might be a good idea to call C.R.I.S. in the morning and see if they can clear out the custom adjustments prior to calibration.

[interested_observer]

BTW, did you remember to zero out your AF adjustments in the camera body before dropping it off? I wiped out all of my adjustments before sending it to Sigma so that I would have some room for future adjustments in either direction if I ever felt a need to tweak it. If you forgot to do that, it might be a good idea to call C.R.I.S. in the morning and see if they can clear out the custom adjustments prior to calibration.

I only had the one single AF fine adjustment made (for this Sigma lens), and they found that. They came out to tell me that my +10 was a good try but a bit more english was necessary - to the tune of about another +35 units. They asked me to wait to make sure that they had all the necessary data files from Sigma for the K mount. It turned out that they had everything that they needed and if I could come back in Friday afternoon, they would have it all ready for me. Sometimes things just work out.

On a side note. Yes, I have a technical background in software and systems engineering. That said, all I really want to do is go take some pictures and relax doing it. I am very interested in seeing what the finished product looks like. Bring it home Friday, take some of the same pictures with pretty much the same lighting conditions from the same place, and just see how the fire hydrant turns out. I don't have a clue as to what it will or won't look like. But for me, right now - I am just interested in going out and taking some pictures. Going to pop some new batteries in the old trusty K100 and do some night shots....

[stormtech]

Been following along here - so glad you are getting the issue with the 8-16 sorted. I would have been pulling my hair out and have a couple sleepless nights wondering if it was the lens or something I was doing wrong.

This may be a dumb question, but I need to know and hopefully learn something. You are talking about fine tuning or tweaking the Sigma lenses. I've never heard of this with Pentax lenses - only their ability to fine tune your camera AF to a lens if you send in both a body and lens. So am I understanding correctly that Sigma can fine tune a lens? It sounds as if they will calibrate the lens to your body if you send both in together.

[dadipentak]

So am I understanding correctly that Sigma can fine tune a lens? It sounds as if they will calibrate the lens to your body if you send both in together.

In my case (with the 50-150/2.8), I didn't send them the camera--just the lens. They asked me what body I used and they adjusted it accordingly.

[Edgar_in_Indy]

This may be a dumb question, but I need to know and hopefully learn something. You are talking about fine tuning or tweaking the Sigma lenses. I've never heard of this with Pentax lenses - only their ability to fine tune your camera AF to a lens if you send in both a body and lens. So am I understanding correctly that Sigma can fine tune a lens? It sounds as if they will calibrate the lens to your body if you send both in together.

Yes, Sigma can adjust the AF calibration in the lens. They call it "AF Data Adjust", and I believe it is done by making changes to the lens firmware. I'm sure Pentax lenses can also be calibrated, but I don't know whether it's the same process.

I have heard of lens calibrations being done by inserting shims into the base of the lens (or removing shims) to change the distance between lens rear element and the sensor/film. With older lenses with less internal electronics, I believe this is the standard approach. But as you suggested, it could be that Pentax service centers have special access to the firmware of the camera, and could do the calibration within the body. I'm just have no idea.

And yes, Sigma will calibrate individual lenses to a specific body if you send them in together. I just did this with my K-30 and all four of my Sigma lenses.

[stormtech]

Thanks folks - good information!