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Field Tests

If you are into landscape photography, then you are probably like  me - always in search for a better wide angle. Well, for different people the definition of 'better' will be different of course, but the usual rule(s) of thumb apply here - sharp, contrasty, good color rendition. What else? For me, it's also reasonable price. There are quite a few really excellent ultra-wide angle lenses out there that cost an arm and a leg and then some more., but quite few at reasonable price. And Nikkor UD 20mm f/3.5 certainly falls into this category. For ~US$200 you can buy a sample in a pretty decent condition. That, plus often gang-ho comments about this lens from online users made me curious to give it a try.

As mentioned earlier, Nikkor UD 20mm f/3.5 was designed for the Nikon F series and is a non Ai lens, meaning that it requires conversion and remachining of the aperture ring if you want to use this lens on modern Nikons. Once converted to Ai, the lens will still retain automatic diaphragm control, and if your camera supports non CPU lens data input as well as  metering with manual lenses, then you will also be able to retain full EXIF information when shooting the UD Nikkor. Other then the need to  convert the lens to Ai, the lens will work like any other fully manual lens.

If you are using a manual lens on a modern digital body, it is likely that you are using a stock focusing  screen, which regretfully is not well suited for accurate manual focusing. With long lenses you can rely on your eyesight when trying to focus, but with ultra wide angles manual focusing without visual aids like split circle screen is going to be pretty tough, simply because of the enormous DOF delivered by wide angles Some cameras like D3 have digital rangefinder, which can certainly be quite helpful but is still not going to be as accurate as a split circle. Now, I have to disclose that I personally don't use a split screen on my Nikons, but when I shoot landscapes, my typical aperture settings are f/8 and f/11. At f/11, the Nikkor UD 20mm f/3.5 will give you a focusing range from about 1.5m to the infinity if you use hyperfocal focusing (note that the UD Nikkor does not have a real DOF scale on the barrel, but there are marks on the chrome ring that can help you simulate the DOF scale). Plenty of focusing coverage for me and probably fo most users. Also, considering that the maximum aperture of the lens if pretty slow to begin with, you are not going to be able to achieve shallow DOF even with wide open aperture and at the minimum focusing distance. Take a look at the shot below, where the central portion of the chain link was placed into focus at ~35cm. You get some separation with out of focus background and foreground blurred slightly due to the slightly shallower DOF, but nothing particularly special.

 

ISO 200, 1/2000, f/3.5, 20mm (Nikon D3)

 

Image resolution with Nikkor UD 20mm f/3.5 was not particularly impressive, as the lens showed quite noticeable amount of softness on both full frame as well as APS-C bodies around borders.  Now, soft corners and wide angle lenses go hand-in-hand  with each other (pardon the pun), in many cases simply because the wide angle lens designs can't achieve a truly flat field curvature, and there is a minor difference in distance across the frame between the focusing plane and the subject. In other cases, distortion, which is quite typical to wide angles, creates an impression of softer corners. Either way, you will notice that if you want to achieve some uniformity across the frame, you'd need to shoot at f/8 and beyond. Even then, border image quality would remain slightly softer when compared to image center, which by the  way is excellent throughout the aperture range.

And speaking of the distortion. The UD Nikkor is surprisingly well corrected for distortion, which is a no small feat for such a wide lens. If you take a look at the images in the sample gallery, you will notice that streight lines even around extreme edges show pretty minimal curving! Kudos to Nikon here...

Like with most ultra wide angle lenses, you should be careful about composing your pictures with UD Nikkor 20mm f/3.5 when a strong light source, like the sun, is positioned within or close to the picture frame. In the shots below, with the sun rays hitting the front element of the lens at ~60 degrees, you can see that the lens falls prone to pretty pronounced flare pretty much throughout the entire aperture range. Aperture ghosting, reduced contrast, glare, de-saturation, color streaks, you name it and  it's going to be present. The lens is a giant light sink, so be careful there.

 

ISO 200, 1/500, f/3.5, 20mm (Nikon D3)
ISO 200, 1/125, f/8, 20mm (Nikon D3)

 

And like with most wide angles, Nikkor UD 20mm f/3.5 showed pretty noticeable vignetting, particularly on a full frmae camera. Even with such a slow maximum aperture, the light falloff noticeably darkens the corners of the picture frame, so if your camera has a built-in vignetting control, you might want to set it to medium to get rid of this artifact. Vignetting actually remains visible until f/5.6. On an APS-C body, light falloff is noticeable as well, but not to the same extent as on a FF body. You still need to stop down to f/5.6 to completely get rid of it though.

 

Vignetting @ 20mm - full frame vs APS-C

 

The biggest surprise for me personally though was the color rendition of this lens. Now, many lenses can produce corner to corner sharp images, and in my book, resolution is one of the few most important factors when choosing a lens (it might not be for you though). But resolution alone is often not sufficient: you would also want a lens that is capable of reproducing colors as accurately as possible and preserving infinitely small tonal transitions. For portrait type lenses, quality of bokeh is another potential factor to be considered. Since we are dealing with an ultra wide angle lens here, bokeh is the least thing one would care about, and considering that most landscape photography will be shot at smaller apertures, the issue of soft borders is going to be mitigated as well. So what is left? Yep, color and contrast. And this is where the lens delivered a pleasant surprise. The lens seems to be capable of accentuating warmer tones, giving colors a boost in saturation and adding a touch of yellowish glow. All while still preserving pretty decent contrast in midtones. Other, typically older, lenses are also known to create yellowish casts - many speculate that this is because manufacturers used to add some radioactive materials to the lens caoting material. I can't really confirm whether this is the case  with Nikkor UD 20mm f/3.5, but the look and feel of the color palette was quite pleasant. It is also worth mentioning that unlike some of Canon's lenses, which often also generate warmer palette, Nikkor did not seem to overblow reds, but obviously with the slight boost in yellow color, your pure reds will no longer be pure. Obviously, not everyone will find this desirable in a lens, but can you think of situations where this characteristic can be of use? I can - sandy beaches, sunsets, you know that magical moments when everything around you starts glowing and turns golden. Ok, the final note on color reproduction is color fringing. You can actually notice some lateral color aberration in images once you blow them to 100%. Particularly around high-contrast transitions - take a look at a couple of the street shots in the image galler and notice pinkish edges around leaves and restaurant/shop signs.

 

ISO 200, 1/3200, f/3.5, 20mm (Nikon D3)