De-centered 16-85?

DennisH · 11-02-2018, 04:34 PM

I bought a used 16-85, and it's giving me odd results. I took several pictures with it, not really paying much attention to my technique, which is generally fine. Most of the results are ok, like this:

On the other hand, I also got several like these:

35mm, f/4.5

85mm, f/5.6, approx. 5 ft away

68mm, f/5.6, approx. 5 ft away

All are converted to jpeg only, except the Ferrari, which I cropped. Is it possible these blurry results are just the product of bad technique, depth of field issues, or does the lens seem to be defective?

**BigMackCam** · 11-02-2018, 04:41 PM

Assuming the sand was level, that last shot might possibly show some de-centering, looking at the lower left quarter of the image.

I had the same problem with one copy of the 16-85. Frankly, it's a possibility with many lenses, especially those with as many optical and mechanical linkages as this.

I would carry out some tripod-based tests using a perfectly flat subject at different focal lengths, wide open. The objective isn't to get a completely sharp image in the centre and borders, but to get the same level of sharpness in each corner area. Tripod-based testing will allow you to adjust the camera precisely.

DennisH · 11-02-2018, 05:14 PM

Thanks for the input. Naturally these look much better on my phone screen - on my desktop the problems are much more apparent.

**BigMackCam** · 11-02-2018, 05:20 PM

Originally posted by DennisH

Thanks for the input. Naturally these look much better on my phone screen - on my desktop the problems are much more apparent.

You're most welcome

Hand-held shots at close range can be a demanding choice for testing of de-centering, as it's so very difficult to get the lens precisely perpendicular to the subject. A couple of years back I bought a lens for my Sony gear and I was absolutely convinced that it had a mount alignment problem, as the right hand side of every photo was less sharp than the left. After a few days of fretting over it, I did some careful tripod tests, and found out that the fault was mine entirely. I had (and still have) a tendency to point the camera at a slight angle to my subjects. It's very slight, but at close range and with wider apertures, it's enough to show up. At least I'm conscious of that tendency now, and have mostly adjusted my hold as a result

In that last shot, it could be that your camera was tilted slightly across the top left to bottom right diagonal, since the sharpest point (to me) appears to be in the upper right quadrant.

Good luck with your own tests... Let us know how you get on?

Snafu711 · 11-03-2018, 12:51 AM

I had to return my 16-85 twice because of decentering. The thing I noticed is that decentering can vary greatly with focal length. My first copy had the issue mostly at 16 mm (mushy right third of the picture), but with no obvious decentering above 35 mm. The second copy was perfect at 16 mm, but had a soft lower left corner between 24 and 35 mm. Softness moved to upper right corner above 35 mm.

Be sure to check the lens at range of focal lengths.

aaacb · 11-03-2018, 04:54 AM

There's this guide for a more systematic method, though having to do this at different focal lengths will take some time How to Check Your Lens for Decentering - Articles and Tips | PentaxForums.com

Buntzbooze · 11-08-2018, 12:33 PM

Mine was very poor from 16 to 28. After a lengthy fix by Pentax, who acknowledge the defect, I would now call it 'ok' at these focal lengths. I find manual focus sometimes alleviates some bluryness at wide angles, but it doesn't instill confidence when I use this lens primarily for landscapes. The dilemma I have is the other focal lenghts are super sharp and if I send the lens back for repair it may come return with issues elsewhere. Your copy seems to be similar to mine.

11-02-2018, 04:34 PM	#1
DennisH Pentaxian Join Date: Jun 2008 Location: Stratford, CT Photos: Gallery Posts: 730	De-centered 16-85? I bought a used 16-85, and it's giving me odd results. I took several pictures with it, not really paying much attention to my technique, which is generally fine. Most of the results are ok, like this: On the other hand, I also got several like these: 35mm, f/4.5 85mm, f/5.6, approx. 5 ft away 68mm, f/5.6, approx. 5 ft away All are converted to jpeg only, except the Ferrari, which I cropped. Is it possible these blurry results are just the product of bad technique, depth of field issues, or does the lens seem to be defective?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Misc should i have made the head light centered?	shaolen	Photo Critique	11	10-04-2019 09:04 AM
Nature Trying To Remain Centered.	Tonytee	Post Your Photos!	2	09-27-2018 03:19 PM
Example of my de-centered (?) DA16-85 - opinions?	BigMackCam	Pentax SLR Lens Discussion	6	11-23-2015 07:50 PM
Question Forum site centered and narrower	D1N0	Site Suggestions and Help	47	04-05-2015 07:15 AM
K10D: Center AF point not centered	Photomy	Pentax DSLR Discussion	14	02-10-2007 05:22 PM

11-02-2018, 04:41 PM	#2
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Assuming the sand was level, that last shot might possibly show some de-centering, looking at the lower left quarter of the image. I had the same problem with one copy of the 16-85. Frankly, it's a possibility with many lenses, especially those with as many optical and mechanical linkages as this. I would carry out some tripod-based tests using a perfectly flat subject at different focal lengths, wide open. The objective isn't to get a completely sharp image in the centre and borders, but to get the same level of sharpness in each corner area. Tripod-based testing will allow you to adjust the camera precisely.

11-02-2018, 05:14 PM	#3
DennisH Pentaxian Join Date: Jun 2008 Location: Stratford, CT Photos: Gallery Posts: 730 Original Poster	Thanks for the input. Naturally these look much better on my phone screen - on my desktop the problems are much more apparent.

11-02-2018, 05:20 PM	#4
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by DennisH Thanks for the input. Naturally these look much better on my phone screen - on my desktop the problems are much more apparent. You're most welcome Hand-held shots at close range can be a demanding choice for testing of de-centering, as it's so very difficult to get the lens precisely perpendicular to the subject. A couple of years back I bought a lens for my Sony gear and I was absolutely convinced that it had a mount alignment problem, as the right hand side of every photo was less sharp than the left. After a few days of fretting over it, I did some careful tripod tests, and found out that the fault was mine entirely. I had (and still have) a tendency to point the camera at a slight angle to my subjects. It's very slight, but at close range and with wider apertures, it's enough to show up. At least I'm conscious of that tendency now, and have mostly adjusted my hold as a result In that last shot, it could be that your camera was tilted slightly across the top left to bottom right diagonal, since the sharpest point (to me) appears to be in the upper right quadrant. Good luck with your own tests... Let us know how you get on?

11-03-2018, 12:51 AM	#5
Snafu711 Veteran Member Join Date: Sep 2017 Posts: 307	I had to return my 16-85 twice because of decentering. The thing I noticed is that decentering can vary greatly with focal length. My first copy had the issue mostly at 16 mm (mushy right third of the picture), but with no obvious decentering above 35 mm. The second copy was perfect at 16 mm, but had a soft lower left corner between 24 and 35 mm. Softness moved to upper right corner above 35 mm. Be sure to check the lens at range of focal lengths.

11-03-2018, 04:54 AM	#6
aaacb Pentaxian Join Date: May 2016 Photos: Gallery Posts: 3,724	There's this guide for a more systematic method, though having to do this at different focal lengths will take some time How to Check Your Lens for Decentering - Articles and Tips \| PentaxForums.com

11-08-2018, 12:33 PM	#7
Buntzbooze Forum Member Join Date: Oct 2018 Posts: 60	Mine was very poor from 16 to 28. After a lengthy fix by Pentax, who acknowledge the defect, I would now call it 'ok' at these focal lengths. I find manual focus sometimes alleviates some bluryness at wide angles, but it doesn't instill confidence when I use this lens primarily for landscapes. The dilemma I have is the other focal lenghts are super sharp and if I send the lens back for repair it may come return with issues elsewhere. Your copy seems to be similar to mine.