Teleconverters

[Tindomul]

So I was thinking on getting a Teleconverter to increase the zoom on my lens.
I have a Nikon D40 with a 55-200 mm lens. What Teleconverter would you choose if you are on a budget (wanting to spend no more that $200 unless its really really worth it, then I will go as high as $250).
I like to take pics of little warblers, and those birds are so small and usually so far away most of my pics are super blurry when I get home to check them. Very frustrating.
Thanks.

[tropterrarium]

I would not go that route. A zoom is already optically not ideal, then a 55-200 has an f-stop of possibly 4.5-5.6. A 2x TC costs another 2 stops. With birds you may want to use a rather faster shutter speed, and to get that with f/11 you need to have very bright light, or jack up the ISO on the sensor, leading to very grainy pictures.

You may be better off with a 500 mm mirror lens. Usually at f/8, a bit more compact. Has all the downsides of mirror lenses, but gets you closer in a pinch. Mirror lenses are usually quite a bit cheaper than regular ones.

On many zooms, the TC do not fit. So even if you decide to get one, make sure that you can actually connect them, even if lens and TC are of the same brand.

Or save up for a fix focal 300-500 mm lens. That's what I would do anyway.

[Tindomul]

Thanks, I never realized that the fstop would be sacrificed with teleconverters. Def something to think about. Most birds I photograph are not in bright light, they are in the forest.
What are the downsides of mirror lenses?

[RosieC]

Yeah, my immediate thought was just that... you will be sacrificing the fastest f-stops which with moving birds will make things worse. Also note that most camera bodies can't auto-focus if the lens does not let enough light in, usually they quote an f-stop which gives the minimum light needed for the auto-focus. Some teleconverter/lens combinations can reduce the f-stop below what the camera auto-focus needs. Generally (in Canon at least) the more expensive the camera body the less light the auto-focus needs. I'm sort of guessing that for birds that might move at any moment you don't want to be messing with manual focus, although I could be wrong I've not done bird photography.

[tropterrarium]

Originally Posted by Tindomul

What are the downsides of mirror lenses?

Limited number of focal lengths (mostly 500 mm), fix f-stop, usually f/8, occasionally f/5.6, donut hole halos for out of focus points.

The only plus is that they are relatively cheap.

[ronaldhanko]

I bought a teleconverter a year or so ago and hardly ever use it for the reasons given.

[tropterrarium]

I do have a 1.4x TC for my 300 mm f/2.8, and have used it a few times as a 420 mm f/4. With a 1.4x you only lose one f/stop. Note that the 300 mm f/2.8 is a >$4K lens. One more advantage is that the close focus distance is maintained. In general the longer the focal length, the greater the minimum focus distance. So I get the close focus distance of a 300 but the magnification of a 420 lens. This becomes important with rattlesnake portraits or lizards.

I have also used extension rings on the long lens to get closer. There it is important to have a well-corrected lens (= expensive), because extension rings will also magnify color errors (lateral color, chromatic aberration). Some of it you can correct digitally (NikTools), but I always prefer to have a good native image to start with.

As Ron has implied, rather use a dedicated lens to get what you want to do, rather than adding components.