teleconverters

when using a teleconverter with any lens, do you lose any lens functions, such as auto focus, and what are the down sides, above and below water?

The main drawback is that you loose light. A 1.4x converter will cost you one stop (a factor of 2) of light, a 2x converter will cost you two stops. Except for some professional cameras autofocus will work up to a lens aperture of 5.6. If you add a 1.4x or 2x converter that means autofocus will still work if your lens has an aperture of 4 or 2.8, respectively, or better.

If your camera has trouble focusing in low light this will get worse with a converter. This may be more of a problem underwater where light can be more limiting than on the surface.

Beyond this I am not aware of special problems apart from the fact that for telephoto shots focusing, camera shake, depth of field become more challenging.

Bart

There are various threads on teleconverters. They are not all the same quality and can be lower quality than the lens you are using. Not all converters will auto-focus with all lenses. These differences can lead to differing results.

Here is one thread on the topic. There is some good information lower in that thread that might interest you. You might want to do more using a SEARCH.

teleconverter info

A large part of the issue....what are you trying to accomplish and what setup are you using?

I really like the Kenko DG 1.4x on my tokina 10-17 but it will not autofocus on my nikon 60mm AFS, for example.

thanks . im interested in getting a 400mm lens for some above water trips ill be doing. Iwould like to be able to use a teleconverter to extend the range thanks

The one nice feature about using a 1.4x on a 400 mm, the setup still focuses at the range of the 400mm. A 560mm lens would generally not focus as close.

Some teleconverters are made for a range of focal lengths. I have an older manual focus version 1.4x Nikon teleconverter that is made for lenses over 200mm, for example. My Kenko 1.4x states it is made for longer lenses as well...but it works just fine for my tokina 10-17.

My older Nikon unit will not attached to the tokina due to how the glass extends on the 2 units. You might want to make certain the lenses you are putting together will work well together. IF there is one locally, they may let you bring in your camera/lens and take pictures out their window...then you could check the prints for sharpness in corners, etc.

Nikon - but what relevance is the camera body ?

Even FF and crop would not seem relevant to me.

Paul C

I use the canon 400 f2.8 and occasionally the 1.4x tc. It does an ok job it the light is good etc and gets a shot but there is a noticeable reduction in the I.Q. I have tried a 2x converter but I would never use the resulting image as it appears far too soft. As mentioned before you lose a stop but that should not be a problem with the newer cameras as the high ISO performance allows you to ramp up the ISO if necessary.