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12-19-2017, 02:51 PM   #16
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Here is the sigma on the K-50 - it's better but still not as good as the kit lens.

---------- Post added 12-19-17 at 02:56 PM ----------

QuoteOriginally posted by awaldram Quote
Mmmmmm the k3 series is a fine camera that produces 1st rate images as many postings prove.

Equally the Sigma 10-20 is a very high grade lens from Sigmas top line range and again many posting from it show it is capable of very high detail sharp images on any Body inc all Pentax's.

Your complaints seem to indicate both the k3 and the Sigma are producing substandard results compared to your K50 and Kit lens ... I find this very peculiar and surprising.

There is either something wrong with your equipment, Settings or technique without further details its hard to define where the problem lies.

Could you post one of your 'Disappointing' images so we can see what is so upsetting in the results and perhaps diagnose the cause.
Posted! I've heard others complain that the kit 18-55mm is sharper than this lens but I thought it couldn't possibly be true. But so far I can't get anything acceptable out of it. I've used LV, focus peaking, the quick shift manual focus on the lens and there just isn't a sweet spot. But my other point is - on both cameras I set up on the tripod, focused using LV with identical settings, and the cheapo K-50 did a far better job than the K-3. I'm beginning to think the camera is defective...

---------- Post added 12-19-17 at 02:57 PM ----------

QuoteOriginally posted by aurele Quote
Was Shake Reduction off ? SR + Tripod = blurry because SR freak out.
SR off on both cameras, learned that a while ago.

---------- Post added 12-19-17 at 03:02 PM ----------

QuoteOriginally posted by aurele Quote
It's just out of focus.

Try focusing with Live View. If the picture comes out good, then the lens might need micro-adjustement.

Try focusing throught the ViewFinder, using more focus point (the focus point used maybe couldn't find a discernible pattern to focus on) : If the result is good, no adjustement needed.
I'm worried that the AF on this camera is defective as I don't think it has performed as well as my K-50 with a variety of lenses, which just slotted on to that camera and worked flawlessly. And in this test the K-50/18-55 locked on solid as a rock. Surely a camera that's three times the price shouldn't have a bunch of issues a 300 camera avoids?

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12-19-2017, 03:13 PM   #17
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QuoteOriginally posted by burncpt Quote
I'm worried that the AF on this camera is defective
Try focusing with LV. If the result is not good whatever the lens, your camera could be faulty. If focus is good, then lens need micro adjustement.
12-19-2017, 03:22 PM   #18
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QuoteOriginally posted by aurele Quote
Try focusing with LV. If the result is not good whatever the lens, your camera could be faulty. If focus is good, then lens need micro adjustement.
All these images were taken with LV focusing. So how do I go about adjusting the focus? I know there is a setting within the camera but it just has a sliding scale, no reference to an image or anything. So do I just go one click at a time, go back and take another image, upload it to a computer, go back and add another click etc.? That sounds like a ridiculously laborious process!
12-19-2017, 03:55 PM   #19
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QuoteOriginally posted by burncpt Quote
All these images were taken with LV focusing. So how do I go about adjusting the focus? I know there is a setting within the camera but it just has a sliding scale, no reference to an image or anything. So do I just go one click at a time, go back and take another image, upload it to a computer, go back and add another click etc.? That sounds like a ridiculously laborious process!
Check if you have dialed some fine adjustment , say, by error. This would affect the AF performance of your camera. Set the fine focus adj to zero or "off". Then put the sigma lens on the camera and try for different focus distances with viewfinder and liveview camera on the tripod). See what happens first opening files at 100% magn. ratio. Check for differences between LV and VF.

12-19-2017, 06:45 PM   #20
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QuoteOriginally posted by burncpt Quote
All these images were taken with LV focusing. So how do I go about adjusting the focus? I know there is a setting within the camera but it just has a sliding scale, no reference to an image or anything. So do I just go one click at a time, go back and take another image, upload it to a computer, go back and add another click etc.? That sounds like a ridiculously laborious process!
here, read this:

Fixing Front and Back Focus - The Remedy - In-Depth Articles
12-19-2017, 08:55 PM   #21
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QuoteOriginally posted by burncpt Quote
100% crop centre. You can see it's awful! The brighter image is the K-50/Kit
If AF fine tuning doesn't help, it doesn't matter if this is normal or not for the lens; unacceptable to you, then return it.

The K-50's 16MP sensor is going to be more 'forgiving' on lesser optics, whereas the 24MP K-3II is only going to magnify flaws.

With this example, at f/3.5, one would expect at least the center to be sharper. Also note, Pentax seems to make above average kit lenses and the 18-55mm outperforms its price. If I had to guess, either you got a bad sample, or the lens is simply not that sharp wider than f/6.3 or at the 20mm end of the zoom. Sigma probably presumes most users will be at the 10-15mm range where most kits can't capture.

Did you do your test at 18mm just to compare it with the Pentax kit zoom, or would you be using it often around 18-20mm? The bottom line is using it at focal lengths you need it for, and finding if there is an aperture where it performs well.
12-19-2017, 09:14 PM   #22
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QuoteOriginally posted by burncpt Quote
That sounds like a ridiculously laborious process!
It takes 5 minutes. Take 3 shots at +1, +5, +10. Pick the best, then redo with settings around that one. Then shoot around for awhile and see if the results have not improved. I used a grassy crack in the sidewalk about 3 feet away. Took 2 adjustments on a Sigma 30.
12-19-2017, 09:28 PM - 1 Like   #23
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QuoteOriginally posted by burncpt Quote
All these images were taken with LV focusing.
QuoteOriginally posted by SpecialK Quote
It takes 5 minutes. Take 3 shots at +1, +5, +10. Pick the best, then redo with settings around that one. Then shoot around for awhile and see if the results have not improved. I used a grassy crack in the sidewalk about 3 feet away. Took 2 adjustments on a Sigma 30.
LiveView focusing, as far as I know, is not affected by AF fine tuning. AF fine tuning is to correct for the OVF phase detect system and not the contrast detect with LV. No harm in trying it, but if your example was shot with LV, changing the AF fine tune setting is not going to improve the sharpness.

12-19-2017, 10:57 PM   #24
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QuoteQuote:
LiveView focusing, as far as I know, is not affected by AF fine tuning. AF fine tuning is to correct for the OVF phase detect system and not the contrast detect with LV. No harm in trying it, but if your example was shot with LV, changing the AF fine tune setting is not going to improve the sharpness.
Mine was regular shooting.
12-19-2017, 11:03 PM   #25
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QuoteOriginally posted by Alex645 Quote
LiveView focusing, as far as I know, is not affected by AF fine tuning. AF fine tuning is to correct for the OVF phase detect system and not the contrast detect with LV
In fact if you say you're already using LV and fine focus adjustments (magnification) in LV and you're not able to take a sharp picture, this is something uncommon and perhaps a lens defect or some kind of camera failure. I guess if it's lens defect you'll find that changing FL doesn't improve performance (al 14-17 mm the lens has to be at its best).
12-20-2017, 06:10 AM   #26
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Ok, thanks for all the opinions! I'm going to go try some other tests but - assuming I focus in LV using MF then it's still poor - there gotta be some problem. I guess I was thinking that this kind of combo should be able to take sharp pictures in a variety of situations - when I give it LITERALLY every help in the book to get something good and it's still poor I am a bit miffed. I'm going to go sit in a corner, try the same scene with my camera phone and cry if it gives better results, which it probably will do.
Serves me right for buying myself a Christmas present and not donating the money to the poor I suppose...
12-20-2017, 08:06 AM   #27
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Looks pretty bad
heres K3 + Sigma 10-20 seems considerably better than your image.....

12-20-2017, 02:03 PM - 1 Like   #28
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So I went and did a little more playing. Again, this shot was LV on a tripod, 2sec timer. Is this acceptable sharpness from this lens i.e. am I just expecting too much? I applied one step of sharpening in PSP but there seem to be strange red block artifacts around the bright scaffolding areas? Is this moire from the lack of an AA filter or something else? Also a heck of a lot of purple fringe!
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12-20-2017, 08:09 PM   #29
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QuoteOriginally posted by burncpt Quote
Is this acceptable sharpness from this lens i.e. am I just expecting too much?
Cool shot as it really shows what an ultrawide can capture.

Based on your photo sample on #16 comparing it with the kit lens, IF it was "acceptable", I don't think you'd be concerned. I think it's problematic.
Try to take a shot outdoors with at least 1/250" or faster, so you know that any softness is cannot be motion or camera caused blur.
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