Nikkor AF-S Micro 105 mm f/2.8G Review
I want to present details on the lens MTF50 resolution performance and how well the lens autofocuses. I won’t rehash the Nikon specifications of the lens, since that data is readily available in any number of other places.
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.
I’d also like to mention some comparisons to the 60mm f/2.8 Micro Nikkor AF-D. There is a lot of talk on the internet about how totally inferior the 60mm is to the 105mm. I personally think that the 60mm is more competitive than people think it is, even with its lack of VR compared to the 105. It’s true that you have more working distance between the lens and subject (6 inches versus 3 inches at 1:1) using the 105mm, but often that extra distance isn’t really needed. The working distance goes down to 2.75 inches at 1:1 magnification if you use the 105 lens hood.
These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format.
Here is a link to get pretty good information on this lens. They reduce resolution measurement down to a single number for an f/stop setting. It’s not that simple; resolution is a 2-dimensional thing.
The focus ring on this lens is nice and wide; nobody can complain about that. You can use it anytime you want to override autofocus. Many people use this lens in manual focus mode only, and only use the focus ring to set the magnification before moving the camera/lens back and forth to focus on the subject.
You get a rear rubber dust gasket, but that’s it for moisture/weather sealing.
Phase-detect focus was very fast on my D7100 in dim light, and very repeatable. I also noticed that Live-view shot-to-shot resolution measurements had almost zero variation; the lens focus motor is really first-rate. There was absolutely no focus chatter, and that’s crucial (lenses that have focus chatter are useless, in my opinion).
I noticed no focus calibration shift at different f/stops.
Focus was basically silent (unlike my micro Nikkor 60mm f/2.8).
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. I guess you can manually focus, too (I personally gave up on that the day I got an autofocus lens).
Vibration Reduction (VR)
This has first-rate VR, which is one of the biggest upgrades over my 60mm f/2.8 AF micro Nikkor.
Now for the real meat of this article. You will get to see the full 2-dimensional resolution of this lens, separated into both sagittal and meridional values. Here’s my customary rant about those lens reviewers that grade lens resolution with adjectives like “good”, “fair”, “excellent”, or “1.5 blur units”. Huh? 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, when it exists.
The meridional/sagittal differences are what “astigmatism” is all about. This lens isn’t perfect in that regard, but it’s better than most.
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. That said, this lens was so repeatable that they were all just about the same sharpness.
Wide open. Already impressive resolution, all the way to the edges.
Peak sharpness at f/5.6 These numbers bring tears to my eyes.
Diffraction setting in at f/8, but still excellent.
Pick an f/stop according to desired depth of field. You needn’t bother about trading off sharpness with f/stop. Diffraction starts at f/8, but there isn’t that much of a resolution penalty until about f/16.
Some people refer to a lens with good resolution and contrast as having 'bite'. This lens has big-dog bite. If you can afford it, get it.
Humming bird warning me I’m too close.
105mm Micro Nikkor, 1/60, f/8.0, flash. I combined sharp flash with ambient light at a slow shutter speed to make it a bit more interesting.
Detail from above. This is one sharp lens.
I normally don't display blah images like this, but note how SHARP it is.