How to qualify a used lens?

Vmax911 · 11-02-2019, 12:36 PM

I received a lens from KEH. I've read about shooting a brick wall and looking for blurry spots. Any other techniques you use?

**Just1MoreDave** · 11-02-2019, 12:53 PM

I added "make sure it focuses to infinity" after taking my new acquisition on vacation and discovering that it didn't.

**aslyfox** · 11-02-2019, 01:05 PM

make sure that the aperture works with every mode of your camera

take photos under all conditions you expect to encounter

if there were any " in depth " reviews of the lens see if you can duplicate what was done

as an example look at this

Pentax-DA 15mm F4 Limited Review - Introduction | PentaxForums.com Reviews

**pepperberry farm** · 11-02-2019, 01:38 PM

depending upon the lens (AF or MF, etc), I do a walkabout and see if the normal things I shoot look normal...

**Kerrowdown** · 11-02-2019, 01:50 PM - **3 Likes**

I have a really simple technique...take pictures with it and see if I'm happy.

DeadJohn · 11-02-2019, 02:21 PM

Check optics: Shoot with the aperture wide open. The brick wall can help find misaligned lenses. Are all corners equally sharp? Note that some lens designs have slightly soft corners wide open; consider what others have said about the lens before concluding a specific copy is defective.

Check aperture for slow/sticky blades: Flick the aperture lever (if equipped) while the lens is off camera to make sure things "feel okay". Shoot with the aperture stopped way down. If photos wide open are properly exposed, while stopped down gets overexposed, it could be an aperture issue.

Focus mechanism: Turn the manual focus ring to make sure things feel smooth and verify that the focus distance actually changes. Use autofocus (if equipped) on something far and near.

photoptimist · 11-02-2019, 02:22 PM - **1 Like**

A few things to check : a snappy aperture; smooth focus to infinity; smooth zoom; nothing crooked or loose; dust-free/fungus-free/haze-free optics; and no blurring on one side or the other of the frame

One issue is to have fair expectations about the lens. A lot of older lens show more aberrations, softness, and flare than the latest and greatest optics. It's not KEH's fault that the designers of yore lacked the exotic materials and aspheric elements used today. And a very old lens will inevitably have some internal dust, external scratches, etc. Checking Pentax Lens Reviews & Lens Database can give you some idea of how that lens can be expected to perform.

Have fun!

Last edited by photoptimist; 11-02-2019 at 02:32 PM.

Bertrand3000 · 11-02-2019, 02:37 PM

Oh, and don't forget to shoot the lens itself and post here for us!

**aslyfox** · 11-02-2019, 02:53 PM

This thread is a great place to tell us about it should you choose to do so

PentaxForums.com → Off-Topic Forums → General Talk → Your latest acquisition

Read more at: Your latest acquisition - PentaxForums.com

**TwoUptons** · 11-02-2019, 05:39 PM - **3 Likes**

Originally posted by pepperberry farm

depending upon the lens (AF or MF, etc), I do a walkabout and see if the normal things I shoot look normal...

If they look normal, does that mean you’ve wasted your money and could have done it with what you already had?

-Eric

Kozlok · 11-03-2019, 05:13 AM

Use the lens in a Single-in challenge. One photo each day for a month. It really is a great way to get to know a lens. If there is something really wrong, you will notice about day 5.

https://www.pentaxforums.com/forums/groups/102-monthly-photo-challenges/

aaacb · 11-03-2019, 05:45 AM

I for one look at the mechanical aspects first (focus ring, aperture ring if it has one, iris). Then I look inside at the glass elements using a light, this was the sole reason for returning two of the lenses I ever had to return, they had a smudge of some sort (one brand new had a fingerprint...).

Then I take a few photos indoors, one focusing outside in the distance, see if they look fine. I don't pixel peep but if something's out of whack, I can tell. Perhaps as lenses get more and more sharp at f1.4, if I ever buy a DFA*, I'll need to do more controlled tests.

11-02-2019, 12:36 PM	#1
Vmax911 Pentaxian Join Date: Aug 2007 Location: ABQ Photos: Gallery Posts: 826	How to qualify a used lens? I received a lens from KEH. I've read about shooting a brick wall and looking for blurry spots. Any other techniques you use?

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11-02-2019, 12:53 PM	#2
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	I added "make sure it focuses to infinity" after taking my new acquisition on vacation and discovering that it didn't.

11-02-2019, 01:05 PM	#3
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,581	make sure that the aperture works with every mode of your camera take photos under all conditions you expect to encounter if there were any " in depth " reviews of the lens see if you can duplicate what was done as an example look at this Pentax-DA 15mm F4 Limited Review - Introduction \| PentaxForums.com Reviews

11-02-2019, 01:38 PM	#4
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,676	depending upon the lens (AF or MF, etc), I do a walkabout and see if the normal things I shoot look normal...

11-02-2019, 01:50 PM - 3 Likes	#5
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,818	I have a really simple technique...take pictures with it and see if I'm happy.

11-02-2019, 02:21 PM	#6
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,833	Check optics: Shoot with the aperture wide open. The brick wall can help find misaligned lenses. Are all corners equally sharp? Note that some lens designs have slightly soft corners wide open; consider what others have said about the lens before concluding a specific copy is defective. Check aperture for slow/sticky blades: Flick the aperture lever (if equipped) while the lens is off camera to make sure things "feel okay". Shoot with the aperture stopped way down. If photos wide open are properly exposed, while stopped down gets overexposed, it could be an aperture issue. Focus mechanism: Turn the manual focus ring to make sure things feel smooth and verify that the focus distance actually changes. Use autofocus (if equipped) on something far and near.

11-02-2019, 02:22 PM - 1 Like	#7
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,122	A few things to check : a snappy aperture; smooth focus to infinity; smooth zoom; nothing crooked or loose; dust-free/fungus-free/haze-free optics; and no blurring on one side or the other of the frame One issue is to have fair expectations about the lens. A lot of older lens show more aberrations, softness, and flare than the latest and greatest optics. It's not KEH's fault that the designers of yore lacked the exotic materials and aspheric elements used today. And a very old lens will inevitably have some internal dust, external scratches, etc. Checking Pentax Lens Reviews & Lens Database can give you some idea of how that lens can be expected to perform. Have fun! Last edited by photoptimist; 11-02-2019 at 02:32 PM.

11-02-2019, 02:37 PM	#8
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	Oh, and don't forget to shoot the lens itself and post here for us!

11-02-2019, 02:53 PM	#9
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,581	This thread is a great place to tell us about it should you choose to do so PentaxForums.com → Off-Topic Forums → General Talk → Your latest acquisition Read more at: Your latest acquisition - PentaxForums.com

11-02-2019, 05:39 PM - 3 Likes	#10
TwoUptons Loyal Site Supporter Join Date: Nov 2015 Photos: Albums Posts: 4,213	Originally posted by pepperberry farm depending upon the lens (AF or MF, etc), I do a walkabout and see if the normal things I shoot look normal... If they look normal, does that mean you’ve wasted your money and could have done it with what you already had? -Eric

11-03-2019, 05:13 AM	#11
Kozlok Pentaxian Join Date: Jun 2012 Location: Albuquerque Photos: Gallery Posts: 3,148	Use the lens in a Single-in challenge. One photo each day for a month. It really is a great way to get to know a lens. If there is something really wrong, you will notice about day 5. https://www.pentaxforums.com/forums/groups/102-monthly-photo-challenges/

11-03-2019, 05:45 AM	#12
aaacb Pentaxian Join Date: May 2016 Photos: Gallery Posts: 3,724	I for one look at the mechanical aspects first (focus ring, aperture ring if it has one, iris). Then I look inside at the glass elements using a light, this was the sole reason for returning two of the lenses I ever had to return, they had a smudge of some sort (one brand new had a fingerprint...). Then I take a few photos indoors, one focusing outside in the distance, see if they look fine. I don't pixel peep but if something's out of whack, I can tell. Perhaps as lenses get more and more sharp at f1.4, if I ever buy a DFA*, I'll need to do more controlled tests.