Nikon 18-135 Lens Review
  Tamron 18-250 Lens Review
 

Over the past several years, more than three million visitors have accessed our Internet sites for shopping, research, and information.  In developing our own websites, we have become quite adept at using the Internet for research, and we have utilized our expertise to do research for our own purchases of electronics and technology items.  On this page, we're going to share our experiences with you for onel of our recent purchases. 

Following is a review of the camera lenses for a Nikon digital SLR that we evaluated during a recent purchase decision, and a number of links to sites outside of Wellington Square that we used in our research.  Note the usual disclaimers -- we bought the lens that was best for us, but your needs may well be different, and we do not endorse, or validate the data on, any other websites.

We were replacing a Nikon 28-200 G lens which has a number of favorable reviews.  We already knew this was a good performer from our own results, but we were opting for a wider zoom range starting at 18mm for our travel photos.  We researched, purchased, and evaluated two lenses:  the Nikon 18-135mm and the Tamron 18-250mm with a Nikon mount.  In the end, we returned one of them to our local camera store, and kept the other.  Read on to find out which lens came out on top.

Nikon 18-135mm Lens Reviews (street price $330 - 400)
This medium zoom lens offered us the perfect focal length for our travel photos and has been out long enough to have gathered a number of technical lens reviews.  In addition, enough consumers have purchased this zoom to have built a considerable database of user reviews.  Following are links to the top sites that we used as a basis for our research:
http://www.photozone.de/8Reviews/lenses/nikkor_18135_3556/index.htm
http://www.slrgear.com/reviews/showproduct.php/product/993/cat/13
http://www.popphoto.com/cameralenses/3304/lens-test-nikon-18-135mm-f35-56g-dx-af-s.html
http://www.cameralabs.com/reviews/Nikkor_kit_lens_group_test/page6.shtml

To summarize the lens reviews, the Nikon 18-135mm lens has exceptional sharpness, but at the expense of increased distortion and chromatic aberration.  Since we often crop our travel photos, the sharpness issue was very appealing to us, and the distortion and CA can generally be fixed through software.  However, a recurring issue in consumer comments was an apparent high rate of failure of the autofocusing system in these lenses.  While this lens comes with the Nikon 5 year warranty, that's little consolation if the AF system stops working in the middle of a trip overseas.  Armed with all of the data and conclusions from the lens reviews, we purchased a Nikon 18-135mm lens and tested it ourselves.  The results are shown below.

Tamron 18-250mm Lens Reviews (street price $499)
One of the newer lenses on the market, the Tamron is often referred to as a "super zoom," because it covers such a long focal length (27mm-375mm on our Nikon DSLR due to the effect of the digital sensor).  We did not need a lens with a range this extensive, but the reviews on this lens were intriguing.  Lens review after lens review commented on how sharp and impressive the lens was at nearly all focal lengths.  Could this be an ideal medium zoom lens with a longer zoom included as a plus?  Here are the lens reviews we used:
http://www.photozone.de/8Reviews/lenses/tamron_18250_3563_canon/index.htm
http://www.bobatkins.com/photography/reviews/tamron_18_250.html
http://www.slrgear.com/reviews/showproduct.php/product/1009/cat/23
http://www.popphoto.com/cameralenses/4110/lens-test-tamron-18-250mm-f35-63-di-ii-macro.html
http://www.dphotojournal.com/tamron-af-18-250mm-f35-63-di-ii-ld-aspherical-if-macro/

This lens sounded too good to be true, and it deserved consideration in our buying decision.  Quite frankly, for the relatively small additional cost, we were inclined from the beginning to keep the Tamron 18-250 if it was anywhere close to the Nikon 18-135.  The additional zoom range, if we ever needed it, would be worth the additional cost, plus there was the autofocus dependability issue with the Nikon 18-135. We purchased a Tamron locally, and tested it at the same time we tested the Nikon.

The Results of our Tests

First Impressions
The Tamron has a solid, well-built feel, with a little bit of heft, and zoom and focus rings that are easy to find and easy to operate. Manual focusing with the Tamron was not hard, as it seems the focus ring harkens back to some of the old 35mm film zoom lenses with their ball bearing construction.  Very impressive, and similar to the manual focusing on the Nikon 28-200 zoom lens we were replacing. The Nikon 18-135 zoom, on the other hand, was not a "wow" lens like the Tamron, and it felt a little cheap.  Right out of the box, it was Tamron 1, Nikon 0.

Lens Test Charts
To test resolution and distortion, we printed several test charts from the Internet, from the following websites:
http://www.bealecorner.com/trv900/respat/EIA1956.pdf
http://www.normankoren.com/Tutorials/MTF5.html

Unless you have a hobby of photographing lens test charts, this step may not be one that you would care to duplicate.  However, the advantage of the lens test charts is that they provide an objective and measurable comparison between lenses, without introducing colors and objects that can affect how one feels about a particular lens.

The Lens Tests
All lens tests were conducted using a tripod and the camera's self-timer, to minimize camera shake.  We used the USAF 1951 lens chart, which is sort of a standard for lens testing.  All three lenses produced outstanding shots of the chart that looked like this:

In order to test the lenses, we took several photos of the chart were taken for each lens with a flash, and the best photo was selected for each lens. We magnified the photo of each chart to show the actual pixels. See the circled area in the chart below. This is an extreme amount of magnification, and not surprisingly, none of the lenses could image all of the details of the chart. 

As we examined the resulting photos shown below, we were surprised.  In the first round of testing, the best lens was the Nikon 28-200, the lens we were replacing.  We knew this lens was sharp, but it beat out one of the most highly touted third party lenses, and one of Nikon's sharpness kings.  Wow.  We began to have second thoughts about replacing this lens.

Next we took our charts outside, where there was more light, and the opportunity to stop down each lens to f/11 for better sharpness.  The winner, once again, was the lens we were replacing -- the Nikon 28-200.  But now the Tamron was looking better, and was almost as sharp.  The supposedly super sharp Nikon 18-135 pulled in at a distant third place.

There was one more test we wanted to run indoors -- photos of an interior room, followed by magnifying the resulting photo to isolate a mantle clock.  The first photo below is from the Nikon 18-135, the second photo from the Tamron 18-250, and the third photo is from the Nikon 28-00.  All photos were shot at f/4.8 - f/5, from approximately 20 feet away from the clock at 55mm, and were then magnified 400%.  The results show the Nikon 28-200 is still a little sharper than the other two lenses.  However, the Tamron 18-250 looked pretty good in this series, with less distortion, and was a close second.

Moving outdoors, we took a number of photos with each lens in bright sunlight and in shade.  These were more subjective, but the results (not published here) followed what we had already seen.  The Nikon 28-200 had the best resolution, with the Tamron close behind.  And once again, the Nikon 18-135 came in third.

The Winner
If only we could have just increased the wide angle on the Nikon 28-200 to 18mm, we would have kept that lens.  But since that wasn't possible, we opted for the next best alternative, which was the Tamron 18-250.  This lens showed its potential to take really good photos, keeping in mind that our test shots were magnified much more that we typically would do, even if we were cropping a photo.   We were a little surprised, and disappointed, by the performance of the Nikon 18-135, which did not live up to its reviews.  We kept the Tamron.