Teleconverters

1.4X Teleconverter

These lens accessories are mounted on the camera with the lens mounted on them.  They multiply the focal length, in this case by 1.4.  So, a 100mm mounted on a 1.4x teleconverter would effectively be equivalent to a 140mm lens.  It reduces the light entering the camera by one stop, i.e., f/5.6 reduced to f/8.  My f/2.8 lens becomes an f/4 lens when mounted on this teleconverter.  You might need to up your ISO setting by a stop, eg, 400 to 800 to achieve the same exposure settings on the camera.  

2X Teleconverter

This teleconverter produces a stronger effect.  You multiply by 2 times the lens focal length, i.e.. a 100mm lens becomes a 200mm lens with this mounted.  The drawback is that you lose 2 stops of light.  You must raise your ISO 2 stops, eg. 400 to 1600.  My f/2.8 lens becomes an f/5.6 lens when mounted on a 2X teleconverter

I have come to the opinion that the 1.4X teleconverter is a good choice.  I loose only 1 stop requiring only one stop of ISO increase and reducing all the attending noise introduced.

I might add, that at mindat they seem to think my setup is too complicated.  I suppose the teleconverter would be one of the first things to go.  You can read the attending conversation at mindat.

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