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Longer Lens Vs. Using A Convertor - John Gravett finds out if switching to a longer lens is better than using a convertor.
The big question here is what is "better" - If it's purely image quality, then the answer is going to be "longer lens" almost every time. But if "better" can mean the difference between leaving the 400 / 600mm lens at home and carrying a lighter lens with a convertor, then that puts a different spin on the question. Bearing in mind the 400mm f/2.8mm weights in at 4.9Kg, and the 600mm f/4 at 5.1Kg; they're pretty heavy to take out "just in case".
The cost argument has to be addressed as well; to own a large range of long lenses puts a certain strain on the budget too, and the option of a convertor can be a great choice.
Nikon offers its users a fabulous range of convertors, the usual 1.4 and 2 x convertors, that many manufacturers offer, but also the 1.7 x convertor in addition.
The above convertors will multiply the length of your lens by 1.4, 1.7 or 2 x depending on the one you choose. But that isn't the only effect they have. They also reduce the aperture of your lens by 1, 1½ or 2-stops as well. So, for example, a 70-200mm f/2.8 becomes a 98-280mm f/4 lens with a 1.4 convertor; a 119-340mm f/5 with a 1.7 convertor and a 140-400mm f/5.6 lens with a 2x convertor. The natural comparison lens would be the 80-400mm, which at the 400mm setting is a f/5.6 lens. I chose to buy the fast zoom plus convertor, which was the more expensive option, but gave me f/2.8 all the way to 200mm, plus the fast focusing of the AF-S lens (the 80-400mm is not an AF-S, and the focus is a little slow and noisy).
Grasshopper photographed with a 105mm macro lens.
Advantages can be made with closest focus as well, as a convertor has no effect on the close-focus distance of the lens. This will usually mean that a "converted" lens will have a closer focus than the non-converted longer counterpart. Something particularly useful with say Nikon's 105mm AF-S VR macro, which works particularly well with a convertor; maintaining working distance and giving even greater than 1:1 reproduction.
So: Will they work, and which one to go for?
It's not quite as straightforward as it might seem. Logically, a 2x convertor might seem the most sensible, especially with a zoom lens; but remember, you are losing more light, and some maintain the 2x convertor is softer than the 1.4 or 1.7 models. I have the 1.4 and 2x – and find both work perfectly with my 70-200mm f/2.8 lens. Remember, although a "test report" might find flaws or softness, quality depends on so many other factors, not least, how big you're likely to print the image, and I've had A3+ enlargements off my 2x convertor that are spot on!
Secondly, the Nikon convertors are designed only for certain AF-S lenses, this is because the front element of the convertor sticks out beyond the body, and they would foul the rear element of wider lenses. They do not work with AFD lenses, nor and Non- CPU lenses (manual focus – there are another range for MF lenses); also for the most part, they only work with FX telephoto and tele-zoom lenses. If you have the right lens, the results are wonderful. If you don't, then you have to decide which lens to go for, a shorter plus convertor, or a longer lens.
There are independent make convertors available that may fit a wider range of Nikon lenses, but don't expect the same quality, the Nikon convertors are made specifically for the lenses they fit, and although expensive, give truly excellent results.
Article by John Gravett of Lakeland Photographic Holidays - www.lakelandphotohols.com