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kinkindoll · 06-11-2021, 11:07 PM

Hey all,

I recently bought a DA 20-40 limited for my K3iii. I noticed when i focus to infinity at aperture 2.8 or 4 or largest aperture at any distance, i find the image is out of focus and blur unless i stop down at f5.6 and everything is sharp. Is it normal or my copy is bad ? Thanks

3by2 · 06-11-2021, 11:43 PM

It doesn't sound normal, the 40 end can be a little soft wide open but not blurred. Presumably you've adjusted the af fine tuning for the lens?

Adam · 06-12-2021, 12:52 AM

Have you tested it in live view with magnification?

AfterPentax Mark II · 06-12-2021, 02:15 AM

That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III?

pid · 06-12-2021, 02:46 AM

shutter blur? Which times did you use?

kinkindoll · 06-12-2021, 02:54 AM

Originally posted by 3by2

It doesn't sound normal, the 40 end can be a little soft wide open but not blurred. Presumably you've adjusted the af fine tuning for the lens?

yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus.

May be the light was bad this morning.

Thanks anyway

---------- Post added 06-12-2021 at 02:55 AM ----------

Originally posted by Adam

Have you tested it in live view with magnification?

I didn't, i will try tomorrow. Thanks

---------- Post added 06-12-2021 at 02:59 AM ----------

Originally posted by AfterPentax Mark II

That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III?

I have not used my K-3 iii long enough to test other lenses.

I am in Australia and bought the lens from BHP. It is hard to return oversea. I may take to my local Pentax dealer CRK to deal with it.

Thanks.

I will do sunrise photography again tomorrow, will use LV for comparison

zapp · 06-12-2021, 03:08 AM

AF can get out of alignment, it happened on my DA21 a couple times. Others reported the same. If you cannot focus to infinity in live view, the lens requires repair. It basically means that flange focal distance is off.

kinkindoll · 06-12-2021, 03:32 AM

Don't know, thinking the lighting was dark and bad this morning this may due to the cause of infinity focusing problem. I will give it another go tomorrow.

AfterPentax Mark II · 06-12-2021, 03:55 AM

Originally posted by kinkindoll

yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus.

Then the case could be that the AF fine tuning went wrong somehow. I used this method "https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/" and it went well. Also did you set the AF fine tuning to all lenses or just this particular lens? There is a chance that it is a camera problem and to know for sure you must try it out with another lens. And of course use LV to cover all possibilities where thing can go wrong.

**ramseybuckeye** · 06-12-2021, 04:19 AM - **1 Like**

Originally posted by kinkindoll

Don't know, thinking the lighting was dark and bad this morning this may due to the cause of infinity focusing problem. I will give it another go tomorrow.

That would not make a difference, might just slow it down, but would not throw the focus off.

sbc · 06-12-2021, 05:16 AM

Originally posted by kinkindoll

yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus.

Is that auto focus or manual focal at infinity?

kinkindoll · 06-12-2021, 05:22 AM

Originally posted by sbc

Is that auto focus or manual focal at infinity?

the focus is AF

---------- Post added 06-12-2021 at 05:23 AM ----------

Originally posted by AfterPentax Mark II

Then the case could be that the AF fine tuning went wrong somehow. I used this method "https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/" and it went well. Also did you set the AF fine tuning to all lenses or just this particular lens? There is a chance that it is a camera problem and to know for sure you must try it out with another lens. And of course use LV to cover all possibilities where thing can go wrong.

Thanks

---------- Post added 06-12-2021 at 05:29 AM ----------

I will post the update when i try it again tomorrow. It will be weird if nothing happened.

**microlight** · 06-12-2021, 06:57 AM

Another vote here for Thomas Heaton's videos. I was in that area of the Lake District last year, although I didn't manage to capture the images that he does.

Waffles · 06-12-2021, 07:06 AM - **2 Likes**

Originally posted by AfterPentax Mark II

That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III?

So strange that anyone could immediately leap to this conclusion. It may be defective but there's no way to know from a single post like this. I sometimes wonder about all the defective, inferior samples that have been returned over the years....how many were perfectly fine. I'll wager most of them

AfterPentax Mark II · 06-12-2021, 08:10 AM

Originally posted by Waffles

So strange that anyone could immediately leap to this conclusion. It may be defective but there's no way to know from a single post like this. I sometimes wonder about all the defective, inferior samples that have been returned over the years....how many were perfectly fine. I'll wager most of them

This shows you the trust in the product as opposed to the trust you have in your abilities.

06-11-2021, 11:07 PM	#1
kinkindoll Senior Member Join Date: May 2008 Location: Sydney Posts: 173	DA 20-40 limited Hey all, I recently bought a DA 20-40 limited for my K3iii. I noticed when i focus to infinity at aperture 2.8 or 4 or largest aperture at any distance, i find the image is out of focus and blur unless i stop down at f5.6 and everything is sharp. Is it normal or my copy is bad ? Thanks

06-12-2021, 12:52 AM	#3
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,609	Have you tested it in live view with magnification? Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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06-11-2021, 11:43 PM	#2
3by2 Closed Account Join Date: Feb 2019 Photos: Gallery \| Albums Posts: 819	It doesn't sound normal, the 40 end can be a little soft wide open but not blurred. Presumably you've adjusted the af fine tuning for the lens?

06-12-2021, 02:15 AM	#4
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III?

06-12-2021, 02:46 AM	#5
pid Pentaxian Join Date: Jan 2010 Photos: Gallery Posts: 567	shutter blur? Which times did you use?

06-12-2021, 02:54 AM	#6
kinkindoll Senior Member Join Date: May 2008 Location: Sydney Posts: 173 Original Poster	Originally posted by 3by2 It doesn't sound normal, the 40 end can be a little soft wide open but not blurred. Presumably you've adjusted the af fine tuning for the lens? yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus. May be the light was bad this morning. Thanks anyway ---------- Post added 06-12-2021 at 02:55 AM ---------- Originally posted by Adam Have you tested it in live view with magnification? I didn't, i will try tomorrow. Thanks ---------- Post added 06-12-2021 at 02:59 AM ---------- Originally posted by AfterPentax Mark II That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III? I have not used my K-3 iii long enough to test other lenses. I am in Australia and bought the lens from BHP. It is hard to return oversea. I may take to my local Pentax dealer CRK to deal with it. Thanks. I will do sunrise photography again tomorrow, will use LV for comparison

06-12-2021, 03:08 AM	#7
zapp Pentaxian Join Date: Jul 2011 Posts: 2,389	AF can get out of alignment, it happened on my DA21 a couple times. Others reported the same. If you cannot focus to infinity in live view, the lens requires repair. It basically means that flange focal distance is off.

06-12-2021, 03:32 AM	#8
kinkindoll Senior Member Join Date: May 2008 Location: Sydney Posts: 173 Original Poster	Don't know, thinking the lighting was dark and bad this morning this may due to the cause of infinity focusing problem. I will give it another go tomorrow.

06-12-2021, 03:55 AM	#9
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Originally posted by kinkindoll yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus. Then the case could be that the AF fine tuning went wrong somehow. I used this method "https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/" and it went well. Also did you set the AF fine tuning to all lenses or just this particular lens? There is a chance that it is a camera problem and to know for sure you must try it out with another lens. And of course use LV to cover all possibilities where thing can go wrong.

06-12-2021, 04:19 AM - 1 Like	#10
ramseybuckeye Site Supporter Join Date: Apr 2009 Location: Hampstead, NC Photos: Gallery Posts: 17,296	Originally posted by kinkindoll Don't know, thinking the lighting was dark and bad this morning this may due to the cause of infinity focusing problem. I will give it another go tomorrow. That would not make a difference, might just slow it down, but would not throw the focus off.

06-12-2021, 05:16 AM	#11
sbc Pentaxian Join Date: Mar 2008 Photos: Albums Posts: 359	Originally posted by kinkindoll yes, i did AF finetune the lens, it performs sharp witihin the focal distance. This morning i used to take sunrise photos and focus to infinity and i found the photo is soft and out of focus. Is that auto focus or manual focal at infinity?

06-12-2021, 05:22 AM	#12
kinkindoll Senior Member Join Date: May 2008 Location: Sydney Posts: 173 Original Poster	Originally posted by sbc Is that auto focus or manual focal at infinity? the focus is AF ---------- Post added 06-12-2021 at 05:23 AM ---------- Originally posted by AfterPentax Mark II Then the case could be that the AF fine tuning went wrong somehow. I used this method "https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/" and it went well. Also did you set the AF fine tuning to all lenses or just this particular lens? There is a chance that it is a camera problem and to know for sure you must try it out with another lens. And of course use LV to cover all possibilities where thing can go wrong. Thanks ---------- Post added 06-12-2021 at 05:29 AM ---------- I will post the update when i try it again tomorrow. It will be weird if nothing happened.

06-12-2021, 06:57 AM	#13
microlight Site Supporter Join Date: Sep 2011 Location: Hampshire, UK Posts: 2,129	Another vote here for Thomas Heaton's videos. I was in that area of the Lake District last year, although I didn't manage to capture the images that he does.

06-12-2021, 07:06 AM - 2 Likes	#14
Waffles Pentaxian Join Date: Jan 2021 Location: The Carolinas Posts: 461	Originally posted by AfterPentax Mark II That is not normal behaviour. I think it is a bad copy and I would return it. Do you have problems with another lens on your K-3 III? So strange that anyone could immediately leap to this conclusion. It may be defective but there's no way to know from a single post like this. I sometimes wonder about all the defective, inferior samples that have been returned over the years....how many were perfectly fine. I'll wager most of them

06-12-2021, 08:10 AM	#15
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Originally posted by Waffles So strange that anyone could immediately leap to this conclusion. It may be defective but there's no way to know from a single post like this. I sometimes wonder about all the defective, inferior samples that have been returned over the years....how many were perfectly fine. I'll wager most of them This shows you the trust in the product as opposed to the trust you have in your abilities.