Is this lens Decentered ?

Sootchucker

Sootchucker

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Andrew
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HI guys, looking for some advice please. Some time ago I purchased a second hand Nikon 16-85 F3.5-5.6 VR to go with my single DX body (a Nikon D7200) as a walkabout lens.

Now I know this isn't a pro lens, more an advanced kit lens, but the other weekend, I used for the first time properly (I've had it for over 6 months) and noticed something weird. On all shots taken at the wider settings (16-19mm ish ), I've noticed that the images are noticeably softer on the right hand of the frame side than the left, to the point where I can see the softness when the whole image is on screen (not pixel peeping). Using the below images as examples, do you think one of the elements inside the lens is decentered, and if so is this repairable and will it be an expensive repair or not really worth it ?

Images shot at F8 so there should be reasonable DOF and should be around the lenses sweet spot for sharpness.

It would be a shame as otherwise (and at the medium to longer focal lengths), it's a pretty tidy performer, and TBH, apart from the above issue, from the images I've seen on the web, it looks to be almost as sharp around the rest of the frame (and at all FL's) than the new Nikon 16-80 F2.8-4 unit (which is currently selling for just under the £800 mark) ! Having never seen this before in any of my other lenses, I'm not sure if this is just as good as it gets using a middle of the road "kit" lens on a current 24mp sensor, or whether there is a problem ?

BTW, I'm not asking for critique on the images, just the softness down the right side.Images are straight out of camera jpgs, no PP what so ever.

Full Frame



Extreme Left Side of frame



Middle of frame



Extreme Right Side of frame

 
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I do not see any real softness on the first three if shot at 16-19mm,apart from the last photograph which just looks out of focus.The lens has good rep,but , you must have to recognise that it is a F3.5 upward Nikon kit.

I think that in what you have shown it has performed to it specification.
 
There's a lot of difference in subject distance from extreme left content and extreme right. So in my view at least some of what you're seeing is due to DOF.
 
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Just for clarification, the first image is the main one - the other 3 are simple crops from that image (left, middle and right) - they are not 4 separate images.

Settings were D7200 - 16.3mm (24.5mm equiv), ISO 200, 1/320 F8

Geejay, I thought the same at first, but when I checked (and this is my home village), the distance (relative from the camera to subject), from the camera to the front door of the pub (under where it says "spread") and to the car on the very right of the frame are similar distances, and @ F8 I'd have thought any small differences would be covered by the DOF @ F8 from that distance.

Obviously, I don't expect the extreme edges to be anywhere near as good as the middle, but to my eyes at least, the extreme right hand side is very soft indeed (much more than the left). I guess I'll have to do the ubiquitous brick wall test to find out definitively.
 
Shoot a brick wall head on, and an expanse of wide flat horizontal textured area such as grass or gravel spread out ahead of the lens right to the edges of the frame. The brick wall shows you if the lens is softer on one side IF you've shot it precisely head on. The lawn or whatever will show you the curve of the depth of focus. Wide angle lenses often have curved planes of sharp focus.
 
Camera shake all day long. As the shutter button is pressed right side of the camera moves down. Because the left side of the camera is steady, it almost acts as an axis so there is very little movement of the camera on the left hand side. The result is more blurring on the right side than on the left side of the image.
 
redsnappa said:
Camera shake all day long. As the shutter button is pressed right side of the camera moves down. Because the left side of the camera is steady, it almost acts as an axis so there is very little movement of the camera on the left hand side. The result is more blurring on the right side than on the left side of the image.
Click to expand...
At 1/320th?
 
It is difficult to judge the sharpness ofany of the crops as the original is over sharpened.
deptht of field is about acceptable sharpness only what you actually focussed on is truly sharp, evey thing else is progressively less sharp.

what you show is perhaps what one would expect from a medium to good quality zoom of that zoom range. You might expect rather better from a 17-55 f2.8 which has fewer compromises.
 
Sounds bizarre, and a bit unwieldy, but try taking the same shot both in normal orientation and with the camera upside down. Correct the orientation of the upside down photo and compare the two. If the lens is truly decentred then the softness will swap sides showing it was the lens rather than discrepancies in depth of field etc. I had a similar problem with a EF-S 15-85 I once had and this test demonstrated the decentering.
 
Deckard said:
Sounds bizarre, and a bit unwieldy, but try taking the same shot both in normal orientation and with the camera upside down. Correct the orientation of the upside down photo and compare the two. If the lens is truly decentred then the softness will swap sides showing it was the lens rather than discrepancies in depth of field etc. I had a similar problem with a EF-S 15-85 I once had and this test demonstrated the decentering.
Click to expand...
That's the way to do it.
 
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