telephoto?

[enger]

Hi guys, I'm wanting a lense for my camera that increases the zoom as much as possible. Just wondering what the difference is between a 3x telephoto and a 2x converter? thanks

[TCav]

Teleconverters multiply the focal length of the main lens by its power. A 2X teleconverter will double the focal length of the main lens, while a 3X teleconverter will triple it.

First, there are no generic 3X teleconverters,and the available 3X teleconverters only work with a few lenses. They can damage any lens it is not intended for, and be damaged as well.

Second, teleconverters also decrease the maximum aperture of the main lens. A 2X teleconverter will decrease an f/2.8 aperture to f/5.6. and a 3X teleconverter will decrease an f/2.8 aperture to f/8.0. That means you will need to use longer shutter speeds and/or higher ISO settings. Also remember that your camera's autofocus system will not operate if the maximum aperture is less than f/6.3, so you might lose the ability to autofocus when using a teleconverter.

What lens were you planning to use with a teleconverter?

[VTphotog]

I guess the first question would be -"What camera are you wanting it for?". For a DSLR, the information TCav provides is correct, but for a point & shoot or superzoom camera, there are differences. SLR teleconverters fit between the lens and camera body, spreading the image circle over a larger area, in effect,causing the light loss noted. T/Cs for fixed lens cameras fit to the objective end of the lens. Many of them are designed for particular cameras, and have sufficiently larger lens diameters as to cause no loss of light. An example I am familiar with is the Minolta TC-100, which gives a 1.5x increase in focal length, but does not reduce the effective aperture. (for the D7 and Axx cameras for which it was designed) The tradeoff is that the lens looks like a bell stuck to the end of your camera lens, and can only be used at or near maximum zoom. And it is heavy enough to feel like you are swinging a brick.

Larger ratio converters will either lose light, or have to be big enough to look like the Hubble space telescope. Either way, you will pay for what you get in quality.

brian

[TCav]

Actually, the "light loss" VTphotog mentionedis a result of the change in focal length.

The f-number reference to an aperture (f/2.8, f/4.0, etc.) is actually a statement of the ratio of a lens' focal length to its pupil diameter. A 100mm lens attached to a 2X teleconverter has a resulting focal length of 200mm, but since the pupil diameter remains constant, the ratio of thefocal length to the pupil diameter is halved, resulting in a loss of 2 f-stops.

This is true for teleconverters that fit between the lens and the camera as well as for teleconverters that attach to the end of a lens. The difference is thata teleconverter that is placed between the camera and the lens tells the camera of it's presence so the camera knows to report the corrected f-number, while a camerawill be unaware of the presence of ateleconverter on the end of its lens.

[enger]

The lense i have is a 3x telephoto lense for my Sony camera. I want to get maximum zoom for surfing photos, and am just wondering if the 2x converter would be more powerful than the 3x telephoto? thnks

[TCav]

A 2X teleconverter will double the focal length of your lens, and (roughly) halve your angle of view.

But you may not be able to autofocus with it.

If your current camera only has a 3X zoom, perhaps you'd be better off with a new camera.