joer Loc: Colorado/Illinois

If you are not pleasing yourself then what is the point of taking photographs. Of course if you shoot for clients and they are pleased then...that's pleasing too.

amfoto1 Loc: San Jose, Calif. USA

With a 1.4X teleconverter you lose one stop of light. With a 2X you lose two stops.

The only Sigma 100-400mm I'm aware of is f/6.3 at 400mm (where you are most likely to want to use a teleconverter). That 100-400mm f/5-6.3 will effectively become a 140-560mm f/7.1-9 with a 1.4X... or 200-800mm f/10-13 with a 2X.

You will probably lose autofocus. I don't use a D7200, but most cameras' autofocus is "iffy" at best at effective apertures less than f/8. Even in in ideal conditions, if your camera tries to autofocus it's likely to slow down and hunt a lot more. Manual focus also will probably be difficult because your viewfinder will dim down, too. It might be easier to use Live View to manually focus, but that's usually quite slow and can be difficult in brighter lighting conditions.

The teleconverters will also ALWAYS degrade image quality. Stronger 2X will degrade it a lot more than weaker 1.4X TCs. Just how much is very difficult to say.... Generally teleconverters work better with prime lenses, than they do with zooms. There are also a number of different teleconverters to choose among, which vary in their capabilities. The specific lens used with them can make a difference, too... And the Sigma 100-400mm that I'm aware of is a new, relatively untested and largely unreviewed model. A "matched" teleconverter can work pretty well... designed to complement a specific lens. AFAIK, there is no matched teleconverter for the 100-400mm.

How much loss and whether or not images will be acceptable and usable depends upon you and what you're trying to accomplish. I wouldn't expect too much with a relatively low cost zoom lens. Teleconverters generally are most useful with very high image quality, premium primes that can tolerate some loss of IQ and still produce usable images. Just to try to quantify it, 1.4X probably cost 5 to 10% image quality.... while 2X probably make for a 15 to 25% hit in IQ.

I use Canon gear... including their high quality 1.4X and 2X "II" Extenders. I use the 1.4X occasionally with 135mm f/2, 70-200mm f/2.8 and more frequently with 300mm f/4, 300mm f/2.8 and 500mm f/4 lenses. I only use the 2X with the 300mm f/2.8 and 500mm f/4. More recently I've gotten a Canon 100-400mm f/4.5-5.6... which purportedly works pretty well with teleconverters. But I haven't really tried it very much yet.

Of course those Canon teleconverters won't work for you and I am less familiar with the Nikon system, but am pretty sure none of the Nikon teleconverters would work with an f/5-6.3 lens. There are Nikon lens/teleconverter charts online.... though they won't have info specific to a Sigma zoom. If you wanted to give a teleconverter a try, I'd recommend the Kenko "MC-4" 1.4X DGX that sells for about $120-130. It fits most lenses and supports autofocus as best as any of them. It's also quite sharp in the center, though less so in the corners and at the edges. Since your D7200 is a crop sensor/DX camera, it only uses the central portion of the image anyway, so this should be fine. The somewhat more expensive Kenko "Pro 300" 1.4X DGX (around $150) is more evenly sharp across the entire image, so might be a better choice for a full frame/FX camera.

But, there's bound to be some loss of image quality with any TC. So, all in all, your best bet would be to just use your feet, get closer and use the lens without any TC. Or, if you can't get closer, buy a Sigma (or Tamron) 150-600mm lens and use that. Longer focal lengths... whether a different lens or achieved with a teleconverter... are much harder to hold steady and more strongly influenced by various factors that make for reduced image quality. Some things you can overcome with techniques including a sturdy tripod or monopod, sandbag on camera and lens to dampen internal vibrations, remote release so you don't have to touch the camera, mirror lockup, etc.... Other things, such as wind causing camera shake or deterioration due to atmospheric conditions when you're shooting over a much greater distance, are largely beyond your control. All you can do is wait and hope for better conditions.

orrie smith Loc: Kansas

You do not mention which teleconverter. They range from 1.4 to 2.0. The 1.4 will lose less light than the 1.7 or the 2.0. Usually you will retain autofocus and have less degrading on the 1.4. The 1.7 will retain autofocus on most lenses, but will lose more light. The 2.0 will not focus with most lenses and will lose the most light and cause the most lost of photo quality. They should all be used with a tripod when possible for the best image quality. I have not checked the lens you refer to, but be aware that teleconverters will NOT work on all lenses. Nikon has a chart for their lenses that will work with their teleconverters. You should check with Sigma to make sure your lens will work with their teleconverters. In my opinion, because of the limitations of lenses that will work with a teleconverter, they are not worth the money unless you have a specific use for them and understand the limitations. I have a 1.4 and 1.7 Nikon teleconverter and use them very seldom. Only if my subject is wildlife that is too far away for my telephoto lenses and I do not want to lose the shot because I am out of town and will not have the opportunity return and wait for the subject to come closer.

jonfrei

I have a Nikon TC-20E that is about 20 years old. I was fortunate enough to shop a store that let me put several on my camera and try them out. The Nikon unit was hands-down better in sharpness and image quality across the board than any of the aftermarket brands I tried. I do not see any image quality degradation (I use it with my AF-S 80-200, which is also about 20 years old). I do lose 2 stops of light. You compensate for it, and deal with it. The camera and lens meter and focus just fine with it attached. You do have to watch lens compatibility -- it will not work with my VR 80-400.

Retired fat guy with a camera Loc: Colorado

I have a canon 1.4, had a 2x. They are not worth the reach. I have a 300 mm L prime lens, that is very sharp. I use the 1.4 to shoot the strawberry moon a couple weeks ago. I used a tripod, a wireless shutter realease, and the sharpness was just not there. I will give you a real deal on it if you want it.

rehess Loc: South Bend, Indiana, USA

And if you were using a 140x400 f/5,6 lens you might also have to use a tripod; the main difference is that you'd have less money in your pocket and you'd have more weight to lug.

lightyear

George Lepp ( Photo magazine columnist) did some exhaustive teleconverter research years ago using Canon Equipment ( 1.4x, 1.7x, 2x) and various Canon lenses, and reported it. He noted that teleconverters worked best when the converter and lens were made by the same manufacturer, that 1.4x was the best compromise at the time, and that teleconverters had improved over the years and were likely to continue to improve, but would never match the equivalent performance of the same focal length of lens alone. You may want to access his articles or contact him.
Stan

AHK Loc: Lakewood Ranch, Fl.

I have a matched Canon 1.4X with a canon 7D II...its fine on a tripod, ok hand held for a still shot...would not use for action or BIF (slows down the focus)

jonfrei

BIF?

Patrick9 Loc: Muncie, IN

Does a TC have any advantage over simply cropping the image?

optic Loc: Southwestern United States

Teleconverters are made to be used with prime lenses. Further, some are even tailored for use with specific prime lenses. In that case, they can be quite acceptable. Otherwise, their use will result in some loss of quality, the greater the magnification, the greater the loss. Because of the nature of my work, I keep a 2X handy and albeit against the advice of Nikon, use it with the VR Micro-Nikkor 105mm in situations where the need to simply capture and record the subject outweighs the desire for photographic excellence. When, as often happens, I am dissatisfied with an image, I recall Robert Capa's famous dictum --"If your pictures aren't good enough, you aren't close enough."

tazman77 Loc: Wisconsin

Try this site it gives you info on teleconverters and the lens and how they work together.
http://cdn-5.nikon-cdn.com/Assets/Common-Assets/Images/Teleconverter-Compatibility/en_US_Comp_chart.html

gkuep1945 Loc: Dowling Park, Florida

I would recommend you rent/lease the teleconverter of appropriate model and brand for your lens. If you like the outcome, you can then buy the one you like.
I have a Tamron 70-200mm f/2.8 and a Tamron 2X teleconverter and the image comes out very soft, ie. not sharp at all. I have a friend who has a Canon 70-200mm f/2.8 and a Canon 2X teleconverter and he likes it.

Renting will allow you to decide if you really like the images it produces.

ggttc Loc: TN

Second that opinion...

imagemeister Loc: mid east Florida

Teleconverters are a very hot topic on UHH ! - MUCH has been written on this subject ! My recommendation is - unless you have a fast prime or the Sigma 100-300 f4 - forget about using TC's.

Instead, get as close as you can and maximize the IQ of your current lens and CROP - and if needed because of viewing or printing magnification, use software pixel enlargement. Doing this, no cost, no loss of light, no loss of AF, no loss of DOF.