Hi Kevin,

Any of the recent 'digital' TCs (eg Kenko Pro 300 series) should have
sufficient quality, as would the non-digital Canon & Sigma TCs. The latter
two, however, won't physically fit your Tamron lens, because they've both
got an extension that protrudes into the space occupied by the Tamron
barrel.

If you think you'd be satisfied with a Canon 75-300 instead of a TC, you
might just as well sell your existing Tamron lens and buy a Tamron, Sigma or
Canon 28-300 lens. There is a definite advantage here, in that you won't
have to risk getting dust on the sensor by changing lenses every time you
want a focal length in the 200-300mm range.

Cheers

Do you really need a soft 200-400mm f11 lens?

MrT.

1. a 7 element teleconvertor is the preffered superior to a 4 element
optically speaking.

2. you lose 2 stops of light.... your Auto-focus will almost be useless.

go the 300mm lens. sharper and better focus.

kosh