[pentaxmz]

UPDATE:

My Sigma Lens was sent to Sigma Service, along with my Pentax K-3, and they tell me that they can't calibrate the lens to my camera. However, their own K-3 can be calibrated. Any clues as to what might be wrong with my camera? It works fine with all my other lenses. Thanks.



Hello all,

It's been quite some time since I posted in this forum. Priorities...

I was looking at this page, Sigma 150-500mm F5-6.3 APO DG OS HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database - there are some very beautiful photo examples! Kudos to the photographers!

But I realised that my Sigma lens cannot even come close to capturing details. Despite my camera believing a scene is in focus (it even appears good through the viewfinder), the end results are a soft focus. There aren't any obvious problems with the lens elements so either I am not using the settings correctly or this lens has some kind of flaw.

I still have two years of my warranty remaining on my Sigma lens and I really need to get the focus problem solved.

However, before I ship the lens off for repairs, I was hoping to get enough advice in order to assure myself that the problem isn't me.

Thank you,
Shawn

---

Last edited by pentaxmz; 07-27-2017 at 09:42 PM.

[photomax7]

Hello all,

It's been quite some time since I posted in this forum. Priorities...

I was looking at this page, Sigma 150-500mm F5-6.3 APO DG OS HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database - there are some very beautiful photo examples! Kudos to the photographers!

But I realised that my Sigma lens cannot even come close to capturing details. Despite my camera believing a scene is in focus (it even appears good through the viewfinder), the end results are a soft focus. There isn't any obvious problems with the lens elements so either I am not using the settings correctly or this lens has some kind of flaw.

I still have two years of my warranty remaining on my Sigma lens and I really need to get the focus problem solved.

However, before I ship the lens off for repairs, I was hoping to get enough advice in order to assure myself that the problem isn't me.

Thank you,
Shawn

Hi pentaxmz, try turning off both SR/OS (never have both systems on at the same time)...take some pics on tripod... then try with OS on lens and test....if OK turn off OS on lens and test SR...some Sigma lenses need firmware updates to be compatable with in-camera SR. I experienced the same issue using SR on my Sigma 10mm f2.8. I sent it to a repair center and the problem was fixed...hope this helps.

[PePe]

The first thing to check is whether the lens is front- or backfocusing. If so, you need to calibrate the AF for this lens. Both K-3 and K-5 have this function in the menus.

[jpzk]

The first thing to check is whether the lens is front- or backfocusing. If so, you need to calibrate the AF for this lens. Both K-3 and K-5 have this function in the menus.

Hi pentaxmz, try turning off both SR/OS (never have both systems on at the same time)...take some pics on tripod... then try with OS on lens and test....if OK turn off OS on lens and test SR...some Sigma lenses need firmware updates to be compatable with in-camera SR. I experienced the same issue using SR on my Sigma 10mm f2.8. I sent it to a repair center and the problem was fixed...hope this helps.

To pentaxmz:
Just go ahead and perform both tests as suggested by Pepe and photomax7.
That way, you will have a better idea what's going on with this lens.

[pentaxmz]

Thanks all. You folks are amazing! I will try your suggestions this evening.

Your suggestions are especially timely because Sigma just told me that they need my camera as well. I'm not so keen about also sending my camera. It would be ideal if I can calibrate myself.

[pentaxmz]

Here is an unprocessed, 100% crop sample photo. It isn't an ideal photo or ISO but it does represent the sharpest photo that I have ever been able to accomplish with this lens.

I return home this evening. I'll do some tests (and front/backfocusing - adjustments) tonight.

I guess I can't do any potential firmware upgrade myself. That's reserved for the lenses that are not available for the Pentax mount.

[GlassJunkie]

Here is an unprocessed, 100% crop sample photo. It isn't an ideal photo or ISO but it does represent the sharpest photo that I have ever been able to accomplish with this lens.

I return home this evening. I'll do some tests (and front/backfocusing - adjustments) tonight.

I guess I can't do any potential firmware upgrade myself. That's reserved for the lenses that are not available for the Pentax mount.

We use this lens (Gen2). If your lens has a rubber coating it's Gen1. If the exterior is smooth black resin(plastic) it is Gen2.
We use it on a pair of K-3's. It is my wife's primary long lens, the DFA150-450 was too heavy for her.She is very happy with it.

On Mechanics: We calibrate all lenses to frames using Bourque Charts (we made from his eBook) or DataColor Lens Cal. We acquired the lens from Kenmore in 2014, a demo. It calibrated with backfocus of -3 and -4 then.

When the free K-1 retrofit offer came out, we sent it to Sigma for the new mount (Late 2016). Great job, good parts, upgraded firmware, calibrated (their camera) . Back home on the K-3s, I rechecked, was dead zero on both bodies. It is perfect. If Siggy wants your body, OK, I don't think there is an issue, but "I DUNNO". Takes great pics.

Hope this helps...

[DeadJohn]

Here is an unprocessed, 100% crop sample photo. It isn't an ideal photo or ISO but it does represent the sharpest photo that I have ever been able to accomplish with this lens.

I return home this evening. I'll do some tests (and front/backfocusing - adjustments) tonight.

I guess I can't do any potential firmware upgrade myself. That's reserved for the lenses that are not available for the Pentax mount.

That photo was at 1/30 sec. The softness could be lens shake, missed focus, or an optical defect.

Test on a tripod or resting on a sturdy object. Turn off in-camera SR and in-lens OS. Use liveview. Zoom in to the liveview image and manually focus for a few shots, and also try autofocus during liveview. Use the self timer or a remote.

Assuming those shots are sharper, turn off liveview and use autofocus. If the liveview shots are sharp and non-liveview is soft, then it's probably fixable by fine tuning autofocus. If everything remains softly focused, it's most likely an optical defect and needs service. If everything is sharp, then focusing and optics are good, and earlier softness may have been due to SR and OS both being on, or too much handheld shake, or something else.

[pentaxmz]

Here is a quick update... BTW, thanks again for all the additional feedback.

Here are some quick test photos taken before work this morning. This is before I try any in-camera focus adjustments.

I am concerned that it might be the lens because of this repeatable behavior...
Test photos were taken with a flash 1/180th, ISO 200, lens set at 400mm and f6.3, f16, f29. You will notice that f16 is the sharpest (but still unacceptably soft). More concerning is that f6.3 exhibits strange artifacts (see halo on the boldest text) and f29 is softer than f16. I suspect that any in-camera adjustments are not going to fix this. Nevertheless, I will try your suggestions tonight.

I should point out that these samples were taken with a remote to prevent camera shake on a solid tripod (to minimise even mirror shake). I repeated the shots with a few different objects to ensure that the results were repeatable.

BTW, the photos were all taken with lens OS off, and both lens and camera AF on. These are the default settings that I have always used. I'll have more time, this evening, to try out all the suggestions.

Thanks again.

---------- Post added 07-14-2017 at 09:31 AM ----------

We use this lens (Gen2). If your lens has a rubber coating it's Gen1. If the exterior is smooth black resin(plastic) it is Gen2.

I think I have the gen 1, if by rubber, you mean that the focus and zoom rings have a rubber surface.

[lesmore49]

I have the Sigma 150-500 lens and use my K-5, K10D and Km with it. I'm very pleased with the performance...pictures are very sharp, IMO. It is a very good lens for the money, but I have found needs certain techniques.

What I do:

• Set the camera to aperture priority and use F 10, F 11.
• Use 800 to 1600 ISO to get relatively high shutter speeds from around 1/640th (at a minimum) to over 1/2000th.
• I regard this lens as a day time, outdoor use lens. It needs lots of light .

I also have fallen back on my old film days and use methodology that I first learned back in the late 1960's. Back then the rule of thumb was that if always use shutter speeds that are at the very least match the focal length of the lens. For instance if you have a 300 mm lens, use at least 1/300th, if you have a 500mm lens, use at least 1/500th. To be on the safe side, with the Sigma 150-500 I use as a minimum...as mentioned before...1/640th and try for higher.

The reason that I use either F 10/11 for F stop settings is that the depth of field with this long focal length lens is narrow and as I like to ensure everything is in focus...use these F stop settings with this lens.

With the Sigma lens you have their shake reduction setting...OS I think they call it. I never use OS. I shut it off and always use the Pentax shake reduction system...only. No reason, except if you use both the Pentax and Sigma shake reduction systems on at the same time, I think it ends up being counter productive.

I shoot mostly wild birds, animals and drag racing vehicles (in motion). These subjects are really moving and I set my AF on spot...I also try to focus on the eye of the subject, if possible. If the eye is in focus then everything else looks good, with F 10/11.

I rarely use a tripod....mostly just hand hold using the lens support arm and my hand on the body by the shutter release. It's a heavy lens, but so far no issues for me, although I'm a big guy and don't notice the weight too badly.

If your lens / camera is working well then using these settings should provide sharp pictures.

[pentaxmz]

Hello all, I followed all the instructions, including those here: Fixing Front and Back Focus - Conclusion - In-Depth Articles

I made a 3D focus target and reasonably determined that it's not a camera problem (my K-5 had the same results as well). The "focus" is dead-on but I also discovered something else... as shown in my last flat scene examples, there is an odd "sweet spot" for f-stop. Oddly, both full open aperture and maximum aperture result in a poor image, however, the "sweet" spot seems to be around the middle, around f13. But even f13 seems sub-optimal.

Anyone have suggestions about what might be going on?

I think I need to send my lens (and camera) in for servicing.

[Cthulhugan]

All lenses have such a sweet spot, but it's at a different aperture for different lenses. A perfect lens would focus light to a point and be perfectly sharp, but in the real world this never happens and light is focused to a small circle (or ellipse, thanks to astigmatism). Sharpness is effected by two factors related to aperture -- the "circle of confusion" and the diffraction-caused "Airey disk". Wide open, the circle of confusion dominates sharpness. As you stop down the circle of confusion gets smaller and the Airey disk gets bigger, but because the circle of confusion is larger than the Airey disk the image gets sharper. At the point where they are about the same size you get peak sharpness. If you continue to stop down, the Airey dusk now dominates and sharpness decreases -- the lens is now "diffraction limited".

[pentaxmz]

All lenses have such a sweet spot, but it's at a different aperture for different lenses. A perfect lens would focus light to a point and be perfectly sharp, but in the real world this never happens and light is focused to a small circle (or ellipse, thanks to astigmatism). Sharpness is effected by two factors related to aperture -- the "circle of confusion" and the diffraction-caused "Airey disk". Wide open, the circle of confusion dominates sharpness. As you stop down the circle of confusion gets smaller and the Airey disk gets bigger, but because the circle of confusion is larger than the Airey disk the image gets sharper. At the point where they are about the same size you get peak sharpness. If you continue to stop down, the Airey dusk now dominates and sharpness decreases -- the lens is now "diffraction limited".

Yes, I agree with you. Great description BTW.

But what I am trying to ascertain is whether or not this lens is fundamentally flawed because the focus is clearly soft. I tested for a potential forward and backfocus problem and found none. Am I correct to assume that soft focus is more likely a lens flaw?

I am ready just trying to avoid sending my camera and lens away for repair but I am thinking I have no choice.

[photomax7]

Hi pentaxmz...sorry to say that going by all above and especially the ghosting on the first test image I'm tending to think this may be a lens alignment issue that needs sorting by a Sigma repair specialist. I've seen on the Pentax forums examples of Sigma users not happy with their lens focus performance, but after servicing usually there's a noticible improvement. You might have to bite the bullet on this one and put it in for an estimate for repair and see what's said...good luck!

[pentaxmz]

Update:

Hello all,

I just received a phone call from Sigma service.

I am told that they cannot calibrate the lens to my Pentax K-3 (shipped with the lens). I was given no other details except that they had no issue calibrating my Sigma lens to their own Pentax K-3.

Before they ship everything back to me, can anyone help by providing a possible explanation as to why they cannot calibrate the lens to my camera?

Something doesn't seem right. My K-3 works perfectly with every other lens that I own (including two other Sigma lenses).

Any ideas?

Thank you.