This review will primarily detail the lens MTF50 resolution performance and how well the lens autofocuses. Other reviews already rehash the Nikon specifications of the lens, so I don’t intend to repeat all of that here. I don’t sweat minor lateral chromatic aberration, noticeable distortion, and vignette issues; software fixes those. Software can’t create missing resolution, solve inaccurate focus, or rid focus chatter.
I should mention that vignetting at 140mm is breathtaking, but lucky us that software rids it with virtually the click of a button.
My usual disclaimer: this is looking at a single copy of the lens. Yours will be different, but hopefully ‘similar’. The only place I know of that tests lots of copies of lenses is here.
These tests were done using a Nikon D7000 (16 MP) with unsharpened 14-bit compressed RAW format.
Here is a link to get pretty good information on this lens. My main complaint with them (and most of the other web sites) is that they try to reduce resolution measurement down to a single number for an f/stop and focal length setting. It’s not that simple; resolution is a 2-dimensional thing (and also a sagittal versus meridional thing).
Here’s another gripe: Nikon doesn’t even include a lens hood or lens pouch. That’s really insulting, considering the price of this lens.
This lens telescopes out into three sections as you zoom. The tolerances are really tight, though, and it doesn’t have any “wiggle” in it. Everything feels surprisingly solid with this lens. Don’t drop it, though (as if ANY lens handles dropping well).
As opposed to most of their “kit” lenses, the focus ring on this lens is a proper one, nearest the camera. It’s sufficiently wide that I have no complaints about it. Just like their ‘pro’ lenses, you can use it anytime you want to override autofocus.
The lens also has a proper metal lens mount and gasket (rubber seal). That’s it as far as dust/weather resistance is concerned. If you damage any Nikon lens with water or dust, including weather-sealed lenses, your warranty plus 5 bucks entitles you to a latte.
Nikkor 18-140mm zoomed out to 140mm
Focus was a bit sluggish on my D7000 in dim light, and quite a bit faster on my D7100. Since this isn’t exactly a sports/wildlife lens, that’s a minor point. Focus is very repeatable, and that is what’s important. There was zero focus chatter, and that’s crucial (lenses that have focus chatter are useless, in my opinion).
If you’re too far out of focus, you will probably need to give it a nudge in the right direction using the manual focus ring. This is really common for lenses.
I may be pickier than many on this point, but I did notice a focus calibration shift at different focal lengths. It’s not huge (about 4 fine-tune units), but I’d have to say that it’s my least favorite thing about this lens. Stopping down about one stop will mask it. I really wish that Nikon would “invent” a docking station like Sigma has, so you could customize focus tuning at different focal lengths and distances; oh, well.
I don’t have a single lens that doesn’t need some focus fine-tune calibration. This lens is no different. If your camera doesn’t have fine-tune, you need to save up and buy one; refurbished cameras are pretty reasonable these days. Your lenses won’t be giving you what you paid for without fine-tune, unless you put up with Live View autofocus.
Vibration Reduction (VR)
This seems to be the most capable lens VR I have yet tried, at about 4 stops. Everybody is different in how they support the camera while hand-holding it, so your mileage will vary here. I determine “sharp” versus “un-sharp” by photographing a resolution chart at slow shutter speeds and measure where the resolution (MTF50 lp/mm) drops by 10% from maximum. I don’t know if there is some industry standard on VR effectiveness, but what counts for me is when pictures just start to show some blur, and I like to do it by the numbers. I haven’t figured out how to calibrate my level of nervousness with hand-holding, so this VR business is literally “hand waving”. Oh, also, I test at the longest focal length.
Here’s where I get to rant about those lens reviewers that grade lens resolution with adjectives like “good”, “fair”, and “excellent”. What the heck does that mean? How about 2 ‘blur’ units??? Really? I want real numbers and I want to see real pictures of things I’d actually bother to photograph.
I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in another article, but suffice it to say that this is really great stuff; it’s comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, really knows his stuff. Visit his site and give him the praise he deserves.
The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly.
The meridional/sagittal differences are what “astigmatism” is all about. This lens is decent in the sagittal direction when you get away from the lens optical center, and honestly really bad in the meridional direction. Corners are decent from 18-50mm, but then performance goes south (astigmatism galore). But the middle of the lens, at all focal lengths, is really, really good. In fact, it mostly makes up for the corner performance.
What the resolution target looks like. Mine is mounted ‘upside down’.
At long last, I’m getting around to some actual resolution results.
Tests were done with “Live View” AF-S autofocus, contrast detect, IR remote, VR OFF, really big tripod. That’s how I get around any phase-detect problems with focus calibration. The results don’t seem to improve using manual focus and 100% magnification in Live View, so I don’t bother. I use the “best of 10 shots”; not every shot gets the same resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce.
140mm f/5.6 APS-C Corner. Note Sagittal is MUCH better than Meridional
18mm center wide open is quite amazing. Even corners are pretty good.
I got 38mm with 35mm mark on lens. Big resolution dip from 18mm.
50mm about the same as 35mm resolution
70mm wide open. Meridional-direction corners aren't looking too good.
140mm wide open. Again, weak corners but great in the center
18mm. You really notice the barrel distortion.
18mm with software lens distortion fix. Voila, you can ignore distortion. Used Capture NX2.
Southern Cal. Christmas Tree. 140mm.
Near closest focus (1.55 feet versus 1.48 feet closest focus) at 140mm, 1/160, f/7.1, VR ON