Is this a lens malfunction or wrong setting?

[blacksheep]

Hello,
Recently I dropped my lens from knee height onto a carpet, and brought it back to the shop where I had bought it. It came back as "no problem", but I'm still wondering whether there is something wrong with this lens.

Here is the photo I took on a very sunny day, f 6.3, ISO100 and at 1/800 second.

You see that the people are so blur in the photo, and I'm wondering if the lens is really ok, or if it is my setting? I cannot imagine the people move faster than 1/800 second...!?

Thanks for your input in advance!

[Colin Southern]

Hi Mari,

Probably easiest to have the shop test the lens and your camera together. It's something you can do yourself, but you need to be quite methodical about it (eg use a tripod -setup a suitable target (eg tape measure at an angle to the camera) (so we can see any degree of back/front focusing etc) - shoot it at the narrowest aperture.

Looking at the image something obviously isn't correct - but the only way to work out what is to eliminate things one at a time.

[HaseebM]

Agree with Colin. Not sure why the cycle wheel too looks slightly blurry and that is perhaps more telling than the people. Hope its only the setting as the elements in the optic chain are pretty sturdy. I have bumped couple of lenses but no issues.

[dje]

Hi Mariko

I dont think it's the settings causing the problem. There doesn't seem to be any part of the photo properly in focus. Is this problem occurring all the time ?

The only other thought I had was that the lens was inadvertantly left on manual focus without you realising it.

Dave

[inkista]

Looks like a decentered or shifted element to me. I'd say bring this photo back with you to the shop and point out the issue.

[Dave Humphries]

Hi Mariko,

I note from the EXIF data that it was shot on a Nikon D90 at 21mm using the 18 - 105mm kit lens.

We are assuming this is an uncropped in post processing, are we correct?
The EXIF appears to support this assumption, PP being simple, using LightRoom 4.4 from a nef RAW file.

I agree with the view that the entire left hand side appears to be very soft and mis-shapen - it may be a silly question (forgive me), but have you checked the front element (or filter) is clean?
i.e. it is not suffering a large smeary palm or finger print where you tried to catch it

Colin is correct about needing to be systematic diagnosing problems.

Can you at least stand "square on" to a brick wall and shoot that?
So everything is at the same distance from the camera.

Cheers,

[blacksheep]

Hi Mari,

Probably easiest to have the shop test the lens and your camera together. It's something you can do yourself, but you need to be quite methodical about it (eg use a tripod -setup a suitable target (eg tape measure at an angle to the camera) (so we can see any degree of back/front focusing etc) - shoot it at the narrowest aperture.

Looking at the image something obviously isn't correct - but the only way to work out what is to eliminate things one at a time.

Hi again! After you "diagnosed" my lens, I did bring it back to the shop - but apparently they did not check well enough.
I do have an image that I shot the moon at the narrowest aperture of F36 at 5 sec, ISO100 with a tripod two nights ago, would that help??

[blacksheep]

Agree with Colin. Not sure why the cycle wheel too looks slightly blurry and that is perhaps more telling than the people. Hope its only the setting as the elements in the optic chain are pretty sturdy. I have bumped couple of lenses but no issues.

Yes, it is very wired... may I ask what "optic chain" is? Quickly googled, but not really sure what it is...

[Colin Southern]

Hi again! After you "diagnosed" my lens, I did bring it back to the shop - but apparently they did not check well enough.
I do have an image that I shot the moon at the narrowest aperture of F36 at 5 sec, ISO100 with a tripod two nights ago, would that help??

No - not really.

Just shoot something like a flat brick wall -with the camera perpendicular to the wall - preferably at minimum aperture and on a tripod.

[blacksheep]

Hi Mariko

I dont think it's the settings causing the problem. There doesn't seem to be any part of the photo properly in focus. Is this problem occurring all the time ?

The only other thought I had was that the lens was inadvertantly left on manual focus without you realising it.

Dave

The thing is I am not sure of exactly since when this problem started appearing. I did drop the camera last month, but I was already thinking that I used to be able to shoot the moon more clear. Still I wasn't sure whether it was me or a lens.

No, I don't use a manual focus 98% of the time - including this shot.

[blacksheep]

Hi Mariko,

I note from the EXIF data that it was shot on a Nikon D90 at 21mm using the 18 - 105mm kit lens.

We are assuming this is an uncropped in post processing, are we correct?
The EXIF appears to support this assumption, PP being simple, using LightRoom 4.4 from a nef RAW file.

I agree with the view that the entire left hand side appears to be very soft and mis-shapen - it may be a silly question (forgive me), but have you checked the front element (or filter) is clean?
i.e. it is not suffering a large smeary palm or finger print where you tried to catch it

Colin is correct about needing to be systematic diagnosing problems.

Can you at least stand "square on" to a brick wall and shoot that?
So everything is at the same distance from the camera.

Cheers,

Yes, you are completely right about all the setting. - and no, I regularly check the filter (and a lens) for any small dirt
It seems like I should take another test shot..

[blacksheep]

No - not really.

Just shoot something like a flat brick wall -with the camera perpendicular to the wall - preferably at minimum aperture and on a tripod.

Ok!
I'm going to take a photo of a brick wall now.

[blacksheep]

There it is!

ISO100, F22, 1/2 sec. at 18mm of zoom lens 18-105mm


ISO100, F22, 1 sec. at 105mm of zoom lens 18-105mm


Hmm.. it's wired. They look ok to me.

[dje]

Mariko I'd suggest you retake this shot with a larger aperture - say f/6.3. With f/22, diffraction will be starting to mask the performance of the lens.

And make sure the focus point is on the wall, not the cushions.

It's looking promising though.

Dave

[blacksheep]

Mariko I'd suggest you retake this shot with a larger aperture - say f/6.3. With f/22, diffraction will be starting to mask the performance of the lens.

And make sure the focus point is on the wall, not the cushions.

It's looking promising though.

Dave

Really? Oh dear..... ok here they are!

[blacksheep]

I took them all with a self-timer of 2 seconds.

f3.5, 1/25 sec, ISO100


f5.6, 1/13 sec, ISO100


f9, 1/5 sec, ISO100


f16, 0.6 sec, ISO100


Everyone! I see something strange on the left side now!

[dje]

Yes indeed, the left side is out of focus. Off to the repair shop I think.

Dave

[blacksheep]

Oh no.. it's a third time I would have to come back to the shop...
Any idea of what might be the cause of this result? I mean, would it be a defect in auto-focus? Something to do with vibration reduction?
A bit wondering whether I should give up on this lens and save up to buy another lens. This was a kit lens came with D90, which was around 800-900 euro..

[dje]

Oh no.. it's a third time I would have to come back to the shop...
Any idea of what might be the cause of this result? I mean, would it be a defect in auto-focus? Something to do with vibration reduction?
A bit wondering whether I should give up on this lens and save up to buy another lens. This was a kit lens came with D90, which was around 800-900 euro..

Mariko I was really thinking of an authorised Nikon repairer rather than the shop where you purchased it. You might be able to get a quote from them. I tend to think Kathy might be onto the problem in post 5 ie an element out of place. It could well be a better option to just buy a new lens.

Dave

[Stagecoach]

Mariko, the images you have taken to try and assess the lens are not going to give you a decent indication in my opinion.

It is not easy in these scenes to determine exactly what is OOF due to a possible lens problem or due to DOF because we can not tell what objects other than the wall are an equal distance from the camera. I would also question your setting up of the camera to ensure it was perpendicular to the wall.

Here's an example of a quick shot I just took to demonstrate how I would go about setting up to do an initial test to evaluate if I had a left/right focus issue. Very simply I focused on the wall and am looking for a 'difference' in sharpness between the left and right sides. Note, I am not considering or looking for a near/back focus issue.

I used a focal length of 18mm (as you did) but I'm also aware that this being the extreme it's not going to give the best sharpness, but we are looking for difference.



The camera was 2.6mtr from the wall and the candle light holders 1.1 mtr from the camera, knowing these measurements is useful if we want to consider possible DOF. I spent time ensuring the camera was both level and perpendicular to the wall and framing subjects where difference in sharpness could be assessed, subjects could easily have been a piece of newspaper or tape.

A range of shots would be taken as you did and the corner/edge subject blown up and compared, as you know they are on exactly the same plane they should be equal in sharpness.

Following this if I still had concerns about overall sharpness I would then start looking at near/back focus issues if relying on auto focus.



I also suggest that in undertaking a similar test you do what you can to keep the lighting across the frame even as a change in brightness or contrast will affect your perception of sharpness.

Ignore the distortion, this lens is poor at minimum focal length.

Grahame