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I know very well that my lens is not a perfect lens for wildlife Photography at all, but still if i would like to know answers for below questions.

  1. Which Teleconverter should I use?
  2. How much focal length I can cover?
  3. Does Sharpness still there in my photographs?
  4. Investing money on Teleconverter is a good option.

Thanks

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    I'm curious what teleconverter you're considering, given that a 55-200 is less than $150... and would definitely provide better results. – Dan Wolfgang Jan 30 '17 at 0:17
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None of them.

Here are the reasons why:

  • Teleconverters are designed to be used with telephoto lenses. Most makers of teleconverters state that they are intended with lenses of 70mm focal length or longer. But many teleconverters are designed to ideally work with lenses 135mm or longer. Even if they will physically fit on wider angle lenses, and often they will not, the optics of TCs are not optimized for wide angle lenses.
  • Your 18-105mm f/3.5-5.6 lens is relatively "slow" in terms of maximum aperture. A 1.4X TC makes the maximum aperture one f-number stop slower, a 2X TC makes the maximum aperture two stops slower. Your 18-105mm f/3.5-5.6 lens becomes a 25-145mm f/5-8 lens with a 1.4X and a 36-210mm f/7.2-11 with a 2X. Not only will that require longer shutter times to get proper exposure, but the AF system on your D7200 is limited to lenses with maximum apertures of f/8 or wider, and only a limited number of the AF points will work with lenses with a maximum aperture narrower than f/5.6. Even if AF does work, with a narrower maximum aperture AF will be slower and less accurate than with a lens with a wider aperture. As you shoot in dimmer light, the AF will cease to function at brighter light levels than with a wider aperture lens, and your focus target will need stronger contrast for AF to work than with a lens with wider maximum aperture.
  • Teleconverters are like magnifying glasses. They'll magnify not only your subject, but all of the flaws of your lens as well. They can also add a few more of their own. The most common problems noticeable when using a TC are reduced sharpness, chromatic aberration, and loss of contrast. If there are strong light sources in front of the camera lens flare can also be an issue. TCs work best with very high quality lenses that don't have many optical flaws. For the most part this means very long focal length prime lenses, such as a 400mm f/2.8 lens or a 500mm f/4 lens. Zoom lenses tend to have more optical aberrations due to the compromises involved with designing them to work at various focal lengths. The larger the zoom ratio, the more compromises are usually made. A high quality 70-200mm f/2.8 lens is usually right on the edge of usability with a TC. That's with a zoom ratio of less than 3X and a maximum aperture of f/2.8. Your 18-105mm f/3.5-5.6 has a zoom ratio of 5.83 and is 1-2 stops slower.
  • A good TC will likely cost more than a decent consumer grade telephoto zoom lens, such as an AF-S 55-200mm f/4-5.6G ED VR II. The 55-200 will give better image quality, better AF performance, and has a wider maximum aperture that will allow faster shutter times at the same ISO than your 18-105mm + TC. It will also give you about the same amount of telephoto reach as your 18-105mm + 2X TC. For a little bit more than a mid-range TC you could buy an AF-S 55-300mm f/4-5.6G ED VR.
  • Thanks Michael for detailed answer, appreciated your response. – Atul Agarawal Jan 30 '17 at 21:48
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A TC will do two things which are bad :

  • It will reduce the effective aperture by a stop (for a 1.4x) or two stops (for a 2x). For wildlife this is an issue as you start battling for shutter speed a lot more often.

  • It will generally reduce sharpness and can add some CA. But this reduction is not really bad.

From my own experience I see no real advantage to using a TC compared to cropping and enlarging. I've see some detailed tests, but these don't convince me that there's much difference between a crop and TC. Maybe a slight advantage for a TC with a good lens, but it's slight.

As @dan-wolfgang suggested, the 55-200 or the 55-300 used or new would be a better choice on a budget.

And I've used the 18-105 and 55-200 and they're both good lenses. I'd never use either with a TC. I've used TC's in the past and have long ago discarded them as a nuisance. YMMV but for me they're a poor choice for the money.

  • Please don't mind, I would like to understand..How far subjects I can shot using 55-300..Can I take close ups of far subjects.Lets say, If i buy 55-300, does this lens help me to capture close up of Brids sitting 50-80 feets far. – Atul Agarawal Jan 30 '17 at 2:01
  • @AtulAgarawal Simple approximation: 300mm is about 3x longer than 105mm, so you will get about 3x magnification compared to using the long end of your 18-105mm. This means the bird will be 3x taller and 3x wider, so 9x the area. It's a big difference. If you want exact numbers, you can calculate how much of the sensor a target will fill at a given size and distance - wikipedia has the formula for focal length vs sensor size vs angle of view, and the rest is trigonometry. – j-g-faustus Jan 30 '17 at 18:40

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