[interested_observer]

Last week I ordered a new Sigma 8-16 because I was granted special access to photograph a national monument after hours (sunrise and sunset), and I needed the UWA lens to get the shots angles I wanted. Plus, it was a lens I had been thinking about for a while. This was the opportunity that pushed me over the edge to place the order - even though I really did not need yet another wider UWA lens - this was special, in that I really need a rectilinear 8mm.

Came home from work this evening and the box was on the counter. Unpacked it, mounted it and went out and shot a few images, as I was loosing the light. Came back in and took a look at the photos. The fire hydrant across the street 75 feet away was not sharp. An Ocotillo 3 feet away was not sharp - all using auto focus. This is what I was afraid of. New lens and ...... I have never had to send a new lens back. Actually, I have never returned a lens.

I had commented on a similar thread a while back...

• https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/186038-my-new-...good-copy.html

... same problem. The lens autofocuses well beyond infinity. In the other thread a -10 correction fixed it to some degree. But, I have 2 weeks from today, and the lens should have been spot on - and its not. I'll try a 10 correction factor tomorrow morning to see what it does, but quite frankly, this is not right.

Well, I sorta of factored in some "just in case time" on this, but not expecting to use it. So, I'll call B&H for a RMA number and see if they will do an immediate swap with out waiting for the return to arrive. Hopefully, #2 will be better.

Here is one of the shots, along with a 100% crop - straight out of the camera.....

So, I went back and re-read what I wrote (my analysis), along with the rest of the thread. Given the extreme field of view and everything, should I really expect sharper at this UWA focal length? Am I expecting way too much? I also read / looked again at the Sigma 8-16 club thread and images. Considering what I see in the other threads, I am thinking that the lens should be sharper that what I am observing (given a pretty small sample window and lighting conditions). I am trying to be objective here.

I also have the 10-17, and 12-24. I went back into my archives and took a look at some images and compared it to some common locations - at sundown, I scurried over to an overlook that I sort of use as a photo lab. I am seeing sharper on my 12-24 @ 12. But I did not shoot a 12/12 comparison.

I did shoot a number of shots at 16, both AF and manual. The 16 does look sharper, and the AF is much better at 16 than at 8.

So, I'll give it a quick try tomorrow before going off to work - and make a final decision then.

Attached Images

   

[Freak]

In the other thread a -10 correction fixed it to some degree. But, I have 2 weeks from today, and the lens should have been spot on - and its not. I'll try a 10 correction factor tomorrow morning to see what it does, but quite frankly, this is not right.

Sometimes lenses are not a perfect fit for the body, that is why good cameras have micro-focus adjustments, it's about matching your individual body to an individual lens, sometimes their are differences that need to be accounted for.

There is no guarantee the first, third or fifteenth lens will be any better, I can't tell a lot from the picture you posted, you may wish to photograph a street sign or something with detail close up in both manual and AF so we may see the differences a little more clearly. But I wouldn't be sending it back until I had at least attempted to use microfocus adjustment and run a few in-depth tests.

[calsan]

You're shooting into the sun in an otherwise low light environment and your subject of the hydrant is only 2.25% of the vertical height of the non-cropped picture (I measured it). That you can see any sort of detail in the hydrant at all is nothing short of miraculous.

[philbaum]

I don't know that you really have a practical problem.

Background:
I still have the original Sigma 10-20. The 10-20 was notorious for not being able to focus well at 10mm FL, It'll focus at 12 and on up, but not very readily at 10. If you look at the hyperfocal distances for your 8 and maybe 10, you'll find that you can just set the distance scale on 3' or something like that and the lens would be in focus to infinity. If you look through the VF with a 10mm FL, you'll find that the compression of all the surfaces makes it very difficult to tell when things are in focus - and i imagine this is the difficulty for the AF systems as well.

If you're saying that the camera won't focus sharply at infinity -then thats a problem and probably should be returned for repair.

Do some tests with your lens and see if its more reliable AF wise at the longer end and mostly throughout the zoom range. If the only focus problems are at the UWA end, then thats so much of a problem - just dial something in manually - it'll be close enough.IMO

UWA lenses are just different.

[dadipentak]

I'd send it to Sigma to be calibrated. I did that with my 50-150/2.8 and it came back sharp as a tack.

[interested_observer]

Good Morning Everyone,

I am sitting here for a couple of minutes letting letting the sun get a little higher, getting more and better light, before I go and give it another try. I literately do a lot of my work in in the 12 mm area (stitched and just single frame), and yet I am still uncertain myself as to if my expectations are reasonable or not.

Sometimes lenses are not a perfect fit for the body, that is why good cameras have micro-focus adjustments, it's about matching your individual body to an individual lens, sometimes their are differences that need to be accounted for.

There is no guarantee the first, third or fifteenth lens will be any better, I can't tell a lot from the picture you posted, you may wish to photograph a street sign or something with detail close up in both manual and AF so we may see the differences a little more clearly. But I wouldn't be sending it back until I had at least attempted to use microfocus adjustment and run a few in-depth tests.

I absolutely agree with you. In fact just the other day, I essentially wrote just the same thing as a response.

You're shooting into the sun in an otherwise low light environment and your subject of the hydrant is only 2.25% of the vertical height of the non-cropped picture (I measured it). That you can see any sort of detail in the hydrant at all is nothing short of miraculous.

The thread I referred to in the original post, I was saying the same thing, that at this wide FL, you start giving up detail. There were two things that struck me in re-reading the thread, that the AF fine adjustment corrected the problem and that I had taken a close up of an Ocotillo (a big bush) a couple feet away, and just got lousy focus at 8mm. I don't want to be a jerk on this, but with lens essentially being about 20% wider than my 12-24 @ 12, I am trying to figure out just what a reasonable set of expectations are here.

I don't know that you really have a practical problem.

Background:
I still have the original Sigma 10-20. The 10-20 was notorious for not being able to focus well at 10mm FL, It'll focus at 12 and on up, but not very readily at 10. If you look at the hyperfocal distances for your 8 and maybe 10, you'll find that you can just set the distance scale on 3' or something like that and the lens would be in focus to infinity. If you look through the VF with a 10mm FL, you'll find that the compression of all the surfaces makes it very difficult to tell when things are in focus - and i imagine this is the difficulty for the AF systems as well.

If you're saying that the camera won't focus sharply at infinity -then thats a problem and probably should be returned for repair.

Do some tests with your lens and see if its more reliable AF wise at the longer end and mostly throughout the zoom range. If the only focus problems are at the UWA end, then thats so much of a problem - just dial something in manually - it'll be close enough.IMO

UWA lenses are just different.

There is a lot of truth in every phrase here. I have the AF Fine Adjustment page in the manual up on my other screen here looking at the instructions.

My Sigma 8-16 AF is problem also. Livewiew AF can not lock focus at all. Normal AF work only in 16mm or near that, about maybe around 70% in pics focus is good. If I want to use AF I always AF focus on 16mm, then switch to MF and zooming. At 8mm or so can always MF...>95% of my pics with this lens is MF

Its the lens' mixed bag of experience base here on the Forum, plus actually having the lens in hand, that is throwing me, here.

I'd send it to Sigma to be calibrated. I did that with my 50-150/2.8 and it came back sharp as a tack.

I was considering this as I was gassing up the truck late last night before going to bed. I think I just might have enough time, but really would rather not take the chance.

Well it looks like it is going to be yet another bright and hot day here is Aridzona, so let me go take some shots and see if I can get something better here to work with.

[liukaitc]

haha, I am the OP from that post you quote.
I returned sigma 8-16 and switched to sigma 10-20 f4-5.6 after that. (if you can get a good copy of 8-16, it is wonderful lens.)
I am quite happy with it. although the auto focus accuracy still soso compare to my other Pentax lens. (Is that a general issue with sigma lens??)
by the way, you already got 12-24...I think 12 is fine.

---

Last edited by liukaitc; 08-14-2012 at 09:22 AM.

[civiletti]

You expected the camera to autofocus on the fire hydrant? Come on, now.

[interested_observer]

You expected the camera to autofocus on the fire hydrant? Come on, now.

No, I did not have the expectation that the camera would autofocus on the fire hydrant - it did not need to. The point was that setting the lens at 8mm, and having something with a bit of definition to it, near the center of the lens (sweet spot), with an aperture of f8, thereby reinforcing the already deep field of view (inherent with a WA / UWA lens) with hypfocal focusing, I was thinking that the fire hydrant would probably be a bit more defined that what it was. Was that expecting a bit too much. I don't know. I am finding out.

Using a depth of field calculator, 8mm, f8 at 10 feet or greater, the hyperfocal distance is 1 foot and inches out to infinity. So, the question is not of focusing on something. The question is how well the items within the depth of field are rendered on the sensor, and of course its a function of distance. Something close is going to have a better sharpness quality than something farther away.

I have been using the Pentax DA 12-24 for several reasons. The distortion is well controlled, its IQ is excellent and its sharp for what it is and does. However, it's widest field of view is around 90 degrees. The 8-16 has a field of view of around 114 degrees. That is 24 degrees wider across 4mm. The Sigma is relatively new. The only other lens this wide is a fisheye, and you have to contend with the fisheye distortion.

What I am finding out from having this lens less than 24 hours is that - for me it is unique in terms of how it handles focusing at infinity. In terms of its focus throw, ~20% of its focus throw is beyond infinity. It has no problem autofocusing 20% beyond where infinity is. I have no other lens that does this. That is the crux of at least part of the problem - possibly the major part of the problem. I had the lens out last night, and again this morning. Going out again with it now - to see if I can make some sense of how it autofocuses at infinity, and do I need to check it and go to manual. When it achieves good focus (regardless of how its obtained), will the focus be sufficient for the needs to which I am going to apply it to? TBD

[msatlas]

You can usually dial in an AF fine adjustment without too much work. I use the side-by-side comparison dealie in review mode on my K-r. Get a cereal box or something else flat with stuff printed on it. Put it some distance away from the camera and set the camera to center AF point, and focus on something with a bunch of fine detail. Then dial in a -1 adjustment and take the same shot. Do the side-by-side review and zoom in on whatever part of the image you focused on, and see if the -1 shot makes an improvement. If so, you know you're moving in the right direction. Keep trying the next increment down until it stops getting better. Alternatively if the -1 shot is less sharp than the un-adjusted shot, do the same process with positive adjustments. It's not nearly as scientific as using focus charts and calculating focus offsets or whatever, but I've successfully used this method with all of my lenses. Some are spot-on, some only need a +/- 1 adjustment (even that little bit helps to get the sharpest shots) and the most I've had to correct any lens is a -5 adjustment for my Tamron 17-50/2.8.

[Edgar_in_Indy]

Photozone tested this lens on Canon and Nikon, and for the Canon they rated 8mm center sharpness as "outstanding" and for Nikon they rated it as "excellent", so I can see why the OP might have rather high expectations. Unfortunately, Photozone did not post any sample images for those two reviews, so no real-world comparison is possible between their lenses and the OP's lens.

FWIW, I've sent my K-x to Sigma last year to have my Sigma 30mm f1.4 calibrated to the body, and they completed the work and shipped it back the same day via FedEx. It came back focusing perfectly. I sent my K-30 and four Sigma lenses a few weeks ago, and they also performed the work very quickly and very well. They told me they try to complete the work within 24 hours when somebody sends the camera body in. Might be a better option than playing lens-roulette.

[dadipentak]

Might be a better option than playing lens-roulette.

In my experience, it's way preferable than playing lens ping-pong with a reseller.

[liukaitc]

Photozone tested this lens on Canon and Nikon, and for the Canon they rated 8mm center sharpness as "outstanding" and for Nikon they rated it as "excellent", so I can see why the OP might have rather high expectations. Unfortunately, Photozone did not post any sample images for those two reviews, so no real-world comparison is possible between their lenses and the OP's lens.

FWIW, I've sent my K-x to Sigma last year to have my Sigma 30mm f1.4 calibrated to the body, and they completed the work and shipped it back the same day via FedEx. It came back focusing perfectly. I sent my K-30 and four Sigma lenses a few weeks ago, and they also performed the work very quickly and very well. They told me they try to complete the work within 24 hours when somebody sends the camera body in. Might be a better option than playing lens-roulette.

how much is the calibrate if lens is without warranty. I assume it is not free.

[Edgar_in_Indy]

how much is the calibrate if lens is without warranty. I assume it is not free.

My 10-20mm was out of warranty, and the service estimate I got showed $100 for the AF adjust, but the tech went ahead and did it for free since I was already paying $240 for a repair to my 100-300mm f4. I would not have paid to have the 10-20mm calibrated since it seemed like it was already okay in the few test shots I took when I first got my K-30. I just figured I'd go ahead and include it in the box since I was already paying to ship the camera and my other three Sigma lenses.

[liukaitc]

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