Sigma 18-35 f/1.8 Art Focus Issues Thread

superdave · 03-13-2019, 05:58 AM

Originally posted by Digitalis

Your copy might be decentered.

New copy is on the way, I hope it will have sharp edges at 18mm!

**UncleVanya** · 03-13-2019, 12:10 PM

Originally posted by Digitalis

I don't think we ever will. Sigma will say it has something to do with Pentax AF and Pentax will say it has something to do with Sigmas electronics.

Interesting. Early on at least (and I haven't checked in a long time) there were reports of similar focus issues on Nikon and Canon which is why I never took Sigma's explanation as gospel.

Focus problems with Sigma 18-35mm f1.8 A on Nikon D7200: Third Party Lens Talk Forum: Digital Photography Review (loads of nikon complaints - mostly about non-central focus points but even center focus point issues come up. )

And decentering seems to be an issue with the non-pentax copies also.

**Digitalis** · 03-13-2019, 12:59 PM

The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D.

**UncleVanya** · 03-13-2019, 02:08 PM

Originally posted by Digitalis

The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D.

LOL - good point.

AntonioS · 03-23-2019, 08:01 AM

Originally posted by Digitalis

The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D.

Not quite, I have a friend that used this lens with a SD1 Merrill and it's absolutely tack sharp. I also have a SD Quattro and, again, no issues.

I have no clue of why this lens works so well with Sigma's bodies and so randomly crazy with other ones.

superdave · 03-23-2019, 12:08 PM

Originally posted by superdave

New copy is on the way, I hope it will have sharp edges at 18mm!

New copy was worse than first one, serious decentering, right side was super blurry.... Default focus using the viewfinder result in bokeh everywhere... I returned it, and I will retry in another store...

AntonioS · 03-23-2019, 12:13 PM

Originally posted by superdave

New copy was worse than first one, serious decentering, right side was super blurry.... Default focus using the viewfinder result in bokeh everywhere... I returned it, and I will retry in another store...

I checked mine and I didn't notice any problems like this one, just the focus issue.

**Digitalis** · 03-23-2019, 01:12 PM

Originally posted by AntonioS

I have a friend that used this lens with a SD1 Merrill and it's absolutely tack sharp. I also have a SD Quattro and, again, no issues.

I don't think any of us were disputing the sharpness of the 18-35mm f/1.8 - it's one of the sharpest lenses I have ever worked with. Interesting to hear the AF problems are non-existant on Sigma cameras.

AntonioS · 03-23-2019, 05:02 PM

Originally posted by Digitalis

I don't think any of us were disputing the sharpness of the 18-35mm f/1.8 - it's one of the sharpest lenses I have ever worked with. Interesting to hear the AF problems are non-existant on Sigma cameras.

Yes. I love and hate mine, specially because it works well on the K5-II and very unreliable with the k3-II. Very frustrating.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
The Sigma 18-35 f/1.8 Art club	scratchpaddy	Lens Clubs	112	01-02-2024 03:17 AM
Sigma 18-35 1.8 art vs HD DA 20-40mm F2.8 - 4 Limited DC WR	jrcastillo	Pentax SLR Lens Discussion	111	09-22-2015 03:02 PM
Sigma ART 18-35 1.8 and K-30	jrcastillo	Pentax K-30 & K-50	36	07-28-2014 09:42 AM
Sigma 18-35 f/1.8 vs the Pentax DA 16-50 f/2.8	someguy42	Pentax SLR Lens Discussion	9	12-06-2013 12:02 AM

03-13-2019, 05:58 AM	#226
superdave Senior Member Join Date: Apr 2009 Posts: 228	Originally posted by Digitalis Your copy might be decentered. New copy is on the way, I hope it will have sharp edges at 18mm!

03-13-2019, 12:10 PM	#227
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,460	Originally posted by Digitalis I don't think we ever will. Sigma will say it has something to do with Pentax AF and Pentax will say it has something to do with Sigmas electronics. Interesting. Early on at least (and I haven't checked in a long time) there were reports of similar focus issues on Nikon and Canon which is why I never took Sigma's explanation as gospel. Focus problems with Sigma 18-35mm f1.8 A on Nikon D7200: Third Party Lens Talk Forum: Digital Photography Review (loads of nikon complaints - mostly about non-central focus points but even center focus point issues come up. ) And decentering seems to be an issue with the non-pentax copies also.

03-13-2019, 12:59 PM	#228
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D.

03-13-2019, 02:08 PM	#229
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,460	Originally posted by Digitalis The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D. LOL - good point.

03-23-2019, 08:01 AM	#230
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113	Originally posted by Digitalis The only people I haven't heard complaints from about this lens are the sigma camera crowd. Either none of them use this lens (unlikely) or there aren't enough of them to make much of a stink about AF inaccuracies - and Sigmas PDAF is said to be at the same tech level as the K10D. Not quite, I have a friend that used this lens with a SD1 Merrill and it's absolutely tack sharp. I also have a SD Quattro and, again, no issues. I have no clue of why this lens works so well with Sigma's bodies and so randomly crazy with other ones.

03-23-2019, 12:08 PM	#231
superdave Senior Member Join Date: Apr 2009 Posts: 228	Originally posted by superdave New copy is on the way, I hope it will have sharp edges at 18mm! New copy was worse than first one, serious decentering, right side was super blurry.... Default focus using the viewfinder result in bokeh everywhere... I returned it, and I will retry in another store...

03-23-2019, 12:13 PM	#232
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113	Originally posted by superdave New copy was worse than first one, serious decentering, right side was super blurry.... Default focus using the viewfinder result in bokeh everywhere... I returned it, and I will retry in another store... I checked mine and I didn't notice any problems like this one, just the focus issue.

03-23-2019, 01:12 PM	#233
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by AntonioS I have a friend that used this lens with a SD1 Merrill and it's absolutely tack sharp. I also have a SD Quattro and, again, no issues. I don't think any of us were disputing the sharpness of the 18-35mm f/1.8 - it's one of the sharpest lenses I have ever worked with. Interesting to hear the AF problems are non-existant on Sigma cameras.

03-23-2019, 05:02 PM	#234
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113	Originally posted by Digitalis I don't think any of us were disputing the sharpness of the 18-35mm f/1.8 - it's one of the sharpest lenses I have ever worked with. Interesting to hear the AF problems are non-existant on Sigma cameras. Yes. I love and hate mine, specially because it works well on the K5-II and very unreliable with the k3-II. Very frustrating.