I have used the Nikon 300mm f/4 AF lens for the last year or so, mostly for shooting birds. While I have been happy with its performance using it with the Kenko 1.4x Pro 300 converter, but I have never felt I have been able to take it's full measure with the Kenko Pro 300 2X. Hence this test...the 300mm by itself, the 300mm with 1.4x (420mm), and the 300mm with 2.0x (600mm). The subject was an experimental wind measuring tower on the top of Mt. Tom, as shot from the Easthampton, MA valley floor some 1200 feet below.

The camera used was the Nikon D300, placed on a tripod and triggered via its automatic 30 second timer with "mirror up". Two shots were taken at each focal length and the best of the pair used in the comparison. My normal base processing was used...a touch of USM (10-5-0). After some internal debate, I decided not to apply any contrast touch-up although I normally would have. The NEFs of the 420mm and 300mm shots were cropped to approximately the same perspective as the 600mm shot, and saved as uncompressed TIFFs using NX2. PhotoMechanic was then used to create 3600 x 2400 "full size" JPEG files good enough for 12" x 8" prints at 300dpi, or 15" x 10" prints at 240dpi. PhotoMechanic was allowed to sharpen according to its built in resizing algorythms.

Later I decided to expand the test, and did a similar series using the Nikon 70-300mm VR and the Sigma 70-300mm APO DG Macro as 300mm lenses, and the Nikon 80-200mm f/2.8 two-ring and the Sigma 18-200mm original wide-zoom as 200mm lenses.

Here are the results. It is readily apparent that the Nikon's are excellent lenses, and the 300mm f/4 especially is one that works well with both Kenko extenders. It is very hard to tell which photo is produced by which combo when viewed blind. The only Nikon weakness was the 80-200's flare of the bright sunshine on the turbine blades. The Sigma zoomx are lower in quality than the Nikons, and this becomes apparent once one gets beyond the 1.4x Kenko...the combination of the 2.0X Kenko and the Sigma lenses is just too opaque to be acceptable. At least that is my opinion.

That said, however, the combination of the Sigma 18-200mm and the Kenko Pro 300 1.4x gives surprisingly acceptable results in 8x10 print size ("large" here in pBase) and probably represents some kind of an all-time bargain for shooting at 300mm (well, 280mm to be exact) since the combo cost me under $300 used.

Take a look for yourself, and comment if you like.

ps. If I may offer a tip, stay in thumbnail mode until you get to a frame you wish to really examine, double-click, then select "Original" on the menu below the photos and view them for the full 3600 x 2400 pixel view. After that, double clicking a thumbnail will expand to file size, and double-clicking the large print will return to thumbnail size. If you want to approximate how they would look as 8x10" prints, chose "Large" as file size instead of "Original" and follow the same procedure, or just use "previous/next" at the top right of the page.