Pentax A* 85mm f1.4 issue

**Swissidoodle** · 07-20-2013, 04:18 AM

I have a A*85mm 1.4 lens which has following issue:
- Pictures are sharp up to f 4.0
- As soon I go below 4.0 pictures start to getblurry
- I tried lens on K5 in Av mode on A setting as wellas M and respective aperture setting like 2.8, 2.0, 1.6 etc. with same results.

First I taught it might be the aperture blades but when in Mmode and aperture set on ring I had same problem.
Glass is very clean and no haze and blades do not show anywear.

Anyone having a ideawhat might be the issue here.

Anvh · 07-20-2013, 05:04 AM

Out of focus most likely?
It's not like the aperture has a very huge effect on the global image quality, afterall the elements stay the same regardsless the aperture.

hcc · 07-20-2013, 05:13 AM

Try to post some examples. Focus issues become more sensitive at large aperture (low f), and thus might explain your trouble.

Na Horuk · 07-20-2013, 05:22 AM

Yeah, it might be that the DoF is just so thin. Also, if you have any filters, take them off. There are some threads on how to use a focus chart, and these can also be used to test the overall lens sharpness, so feel free to look at those.
Thats a great lens, it would be too bad if its not working properly.

Edit: but some examples, with intact exif, would be great

Last edited by Na Horuk; 07-20-2013 at 09:18 AM.

**Swissidoodle** · 07-20-2013, 08:01 AM

Thank you all for your replay. I will contact Eric and see what he thinks

bhairavp · 07-21-2013, 07:03 PM

Sticky aperture blades? Had the same issue with my A50 Macro.

Adam · 07-21-2013, 07:05 PM

Definitely post some pictures, and make sure you're focusing in live view with magnification on

Adam
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**Swissidoodle** · 07-22-2013, 01:21 AM

Lens will be sent to Eric today. Hope he is able to find cause.

07-20-2013, 04:18 AM	#1
Swissidoodle Site Supporter Join Date: Oct 2010 Location: Hayes, VA Posts: 74	*Pentax A 85mm f1.4 issue** I have a A*85mm 1.4 lens which has following issue: - Pictures are sharp up to f 4.0 - As soon I go below 4.0 pictures start to getblurry - I tried lens on K5 in Av mode on A setting as wellas M and respective aperture setting like 2.8, 2.0, 1.6 etc. with same results. First I taught it might be the aperture blades but when in Mmode and aperture set on ring I had same problem. Glass is very clean and no haze and blades do not show anywear. Anyone having a ideawhat might be the issue here.

07-20-2013, 08:01 AM	#5
Swissidoodle Site Supporter Join Date: Oct 2010 Location: Hayes, VA Posts: 74 Original Poster	*Pentax A 85mm f1.4 issue** Thank you all for your replay. I will contact Eric and see what he thinks

07-22-2013, 01:21 AM	#8
Swissidoodle Site Supporter Join Date: Oct 2010 Location: Hayes, VA Posts: 74 Original Poster	*Pentax A 85 mm 1.4** Lens will be sent to Eric today. Hope he is able to find cause.

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07-20-2013, 05:04 AM	#2
Anvh Veteran Member Join Date: Sep 2011 Posts: 4,616	Out of focus most likely? It's not like the aperture has a very huge effect on the global image quality, afterall the elements stay the same regardsless the aperture.

07-20-2013, 05:13 AM	#3
hcc Pentaxian Join Date: Nov 2009 Location: Brisbane, Australia Photos: Gallery \| Albums Posts: 4,005	Try to post some examples. Focus issues become more sensitive at large aperture (low f), and thus might explain your trouble.

07-20-2013, 05:22 AM	#4
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Yeah, it might be that the DoF is just so thin. Also, if you have any filters, take them off. There are some threads on how to use a focus chart, and these can also be used to test the overall lens sharpness, so feel free to look at those. Thats a great lens, it would be too bad if its not working properly. Edit: but some examples, with intact exif, would be great Last edited by Na Horuk; 07-20-2013 at 09:18 AM.

07-21-2013, 07:03 PM	#6
bhairavp Veteran Member Join Date: Jan 2010 Location: Mumbai, India Posts: 399	Sticky aperture blades? Had the same issue with my A50 Macro.

07-21-2013, 07:05 PM	#7
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Definitely post some pictures, and make sure you're focusing in live view with magnification on 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: